,photographic ,reproduction ,processes ,a ,practical ,treatise of the ,photo-,impressions ,without ,silver ,salts ,by ,p4,c4 ,duchochois ,new ,york ,the ,scovill ,adams ,company #dbc ,broome ,street4 #ahia ,,contents ,,introduction4 ,,the ,,designs4 ,,the ,,cyanotype ,,or ,,blue ,,process4 ,,the ,,cyanofer4 7,pellet's ,process47 ,,the ,,black ,,or ,,ink ,,process4 7,ferro-tannate ,process47 ,,the ,,cuprotype4 7,burnett's ,process47 ,,the ,,aniline ,,process4 ,,the ,,primuline ,,or ,,diazotype ,,process4 ,,tracing ,,process ,,on ,,metal4 ,,graphotypy4 ,,the ,,uranotype4 ,,the ,,platinotype4 ,,artigues' ,,process ,,the ,,carbon ,,process4 ,,appendix4 ,,illustrations ,a ,tournette ,chardon's method of coating ,,preparer',s ,,note ,please remember that this book was published over a century ago1 long before today's chemical safety standards4 ,please get expert advice before attempting to perform any of the procedures described in this book4 ,,authors ,,quoted ,artigues4 ,bevan1 ,e4,j4 ,bingham ,borlinetto ,brasseur1 ,chs4 ,buckle4 ,burnett1 ,c4 ,j4 ,chardon ,cheysson ,colas4 ,cooper1 ,h4 ,cross1 ,c4 ,f4 ,de la ,blanchre1 ,h4 ,de ,st4 ,florent ,draper1 ,dr4 ,john ,ducos du ,hauron ,dumoulin1 ,e4 ,endemann1,h4 ,fisch1 ,a4 ,godefroy4 ,green1 ,a4 ,g4 ,graubassi ,harman1 ,alfred4 ,herschel1 ,sir ,john4 ,houdoy ,hbl1 ,baron4 ,hunt1 ,robert ,liesegang1 ,dr4 ,l4 ,loeffler1 ,j4 ,monckhoven1 ,dr ,von4 ,nipce1 de ,st4 ,victor ,obernetter1 ,j4 ,b4 ,pellet4 ,persoz4 ,phipson1 ,dr4 ,pizzighelli1 ,captain ,j4 ,poitevin1 ,a4 ,roy1 ,paul ,sella1 ,v4 ,j4 ,smee1 ,professor ,stephanowski1 ,karl4 ,swan1 ,j4 ,w4 ,willis1 ,william ,wothly1 ,j4 ,x4 ,,introduction4 ,the photographic processes with the salts of iron are all derived from the researches of ,sir ,john ,herschel4 ,the investigations of that great philosopher are so valuable1 so full of instructions that we are led to reprint them1 together with those of ,mr4 ,c4 ,j4 ,burnett1 on the salts of uranium1 etc41 as an ,introduction4 ,it will be seen that the process by which blue prints are to-day obtained is exactly that ,sir ,john ,herschel devised in #ahdj4 8,it is no longer an insulated and anomalous affection of certain salts of silver or gold1 but one which1 doubtless1 in a greater or less degree1 pervades all nature1 and connects itself intimately with the mechanism by which chemical combination and decomposition is operated4 ,the general instability of organic combinations might lead us to expect the occurrence of numerous and remarkable cases of this affection among bodies of that class1 but among metallic and other elements inorganically arranged1 instances enough have already appeared1 and more are daily presenting themselves1 to justify its extension to all cases in which chemical elements may be supposed combined with a certain degree of laxity1 and so to speak in a tottering equilibrium4 ,there can be no doubt that the process1 in a great majority1 if not in all cases1 which have been noticed among inorganic substances1 is a deoxidizing one1 so far as the more refrangible rays are concerned4 ,it is obviously so in the cases of gold and silver4 ,in the case of the bichromate of potash it is most probable that an atom of oxygen is parted with1 and so of many others4 ,a beautiful example of such deoxidizing action on a non-argentine compound has lately occurred to me in the examination of that interesting salt1 the ferrosesquicyanuret of potassium described by ,mr4 ,smee in the ,philosophical ,magazine1 ,no4 #aji1 ,september1 #ahdj1 and he has shown how to manufacture in abundance and purity1 by voltaic action on the common or yellow ferrocyanuret4 ,in this process nascent oxygen is absorbed1 hydrogen given off1 and the characters of the resulting compound in respect of the oxides of iron1 forming as it does ,prussian blue with proto salts1 indicate an excess of electro-negative energy1 a disposition to part with oxygen1 or which is the same thing1 to absorb hydrogen 7in the presence of moisture71 and thereby to return to its pristine state1 under circumstances of moderate solicitation1 such as the affinity of protoxide of iron 7for instance7 for an additional dose of oxygen1 etc40 8,paper simply washed with a solution of this salt is highly sensitive to the action of the light4 ,prussian blue is deposited 7the base being necessarily supplied by the destruction of one portion of the acid1 and the acid by the destruction of another74 ,after half an hour or an hour's exposure to sunshine1 a very beautiful negative photograph is the result1 to fix which1 all that is necessary is to soak it in water in which a little sulphate of soda is dissolved4 ,while dry the impression is of a dove color or lavender blue1 which has a curious and striking effect on the greenish yellow ground of the paper produced by the saline solution4 ,after washing the ground color disappears and the photograph becomes bright blue on a white ground4 ,if too long exposed1 it gets #8over-sunned1' and the tint has a brownish or yellowish tendency1 which1 however1 is removed in fixing2 but no increase of intensity beyond a certain point is obtained by the continuance of exposure40 8,if paper be washed with a solution of ammonio-citrate of iron and dried and then a wash passed over it of the yellow ferro-cyanuret of potassium1 there is no immediate formation of true ,prussian blue1 but the paper rapidly acquires a violet-purple color1 which deepens after a few minutes1 as it dries1 to almost absolute blackness4 ,in this state it is a positive photographic paper of high sensibility1 and gives pictures of great depth and sharpness1 but with this peculiarity1 that they darken again spontaneously on exposure to the air in darkness1 and are soon obliterated4 ,the paper1 however1 remains susceptible to light1 and capable of receiving other pictures1 which in their turn fade1 without any possibility 7so far as ,i can see7 of arresting them1 which is to be regretted1 as they are very beautiful1 and the paper of such easy preparation4 ,if washed with ammonia or its carbonate1 they are for a few moments entirely obliterated1 but presently reappear with reversed lights and shades4 ,in this state they are fixed1 and the ammonia1 with all that it will dissolve1 being removed by washing in water1 their color becomes a pure ,prussian blue1 which deepens much by keeping4 ,if the solution be mixed there results a very dark violet-colored ink1 which may be kept uninjured in an opaque bottle1 and will readily furnish by a single wash at a moment's notice the positive paper in question1 which is most sensitive when wet40 8,it seems at first sight natural to refer these curious and complex changes to the instability of the cyanic compounds2 and that this opinion is to a certain extent correct is proved by the photographic impressions obtained on papers to which no iron has been added beyond what exists in the ferrocyanic salts themselves4 ,nevertheless1 the following experiments abundantly prove that in several of the changes above described1 the immediate action of the solar rays is not exerted on these salts1 but on the iron contained in the ferruginous solution added to them1 which it deoxidizes or otherwise alters1 thereby presenting it to the ferrocyanic salts in such a form as to precipitate the acids in combination with the peroxide1 or protoxide of iron1 as the case may be4 ,to make this evident1 all that is necessary is simply to leave out the ferrocyanate in the preparation of the paper1 which thus becomes reduced to a simple washing over with the ammonio-citric solution4 ,paper so washed is of a bright yellow color1 and is apparently little1 but in reality highly sensitive to photographic action4 ,exposed to strong sunshine1 for some time indeed1 its bright yellow tint is dulled into an ochrey hue1 or even to gray1 but the change altogether amounts to a moderate percentage of the total light reflected1 and in short exposures is such as would easily escape notice4 ,nevertheless1 if a slip of this paper be held for only four or five seconds in the sun 7the effect of which is quite imperceptible to the eye71 and when withdrawn into the shade be washed over with the ferrosesquicyanate of potash1 a considerable deposit of ,prussian blue takes place on the sunned part1 and none whatever on the rest2 so that on washing the whole with water1 a pretty strong blue impression is left1 demonstrating the reduction of iron in that portion of the paper to the state of protoxide4 ,the effect in question is not1 it should be observed1 peculiar to ammonio-nitrate of iron40 8,the ammonio and potasso-tartrate fully possess and the perchloride exactly neutralized partakes of the same property2 but the experiment is far more neatly made and succeeds better with the other salts40 8,the varieties of cyanotype processes seem to be innumerable1 but that which ,i shall now describe deserves particular notice not only for its pre-eminent beauty while in progress1 but as illustrating the peculiar power of the ammoniacal and other parsalts of iron above-mentioned to receive a latent picture susceptible of development by a great variety of stimuli4 ,this process consists in simply passing over the ammonio-citrated paper on which such a latent picture has been impressed1 very sparingly and evenly1 a wash of the solution of the common yellow ferrocyanate 7prussiate7 of potash4 ,the latent picture1 if not so faint as to be quite invisible 7and for this purpose it should not be so71 is negative4 ,as soon as the liquid is applied1 which cannot be in too thin a film1 the negative picture vanishes1 and by very slow degrees is replaced by a positive one of a violet blue color on a greenish yellow ground1 which at a certain moment possesses a high degree of sharpness and singular beauty and delicacy of tint4 ,if at this instant it be thrown into water1 it passes immediately to a ,prussian blue1 losing1 at the same time1 however1 much of its sharpness1 and sometimes indeed becoming quite blotty and confused40 8,to prevent this confusion gum arabic may be added to the prussiated solution1 by which it is hindered from spreading unmanageably within the pores of the paper1 and the precipitated ,prussian blue allowed time to agglomerate and fix itself on the fibers4 ,by the use of this ingredient also1 a much thinner and more equal film may be spread over the surface1 and when perfectly dry1 if not sufficiently developed1 the application may be repeated4 ,by operating thus ,i have occasionally 7though rarely7 succeeded in producing pictures of great beauty and richness of effect1 which they retain 7if not thrown in water7 between the leaves of a portfolio1 and have a certain degree of fixity--fading in strong light and recovering their tone in the dark4 99 99 990 8,if paper be washed with a mixture of the solutions of ammonio-citrate of iron and ferrosesquicyanate 7red prussiate7 of potash1 so as to contain the two salts in about equal proportions1 and being then impressed with a picture1 be thrown into water and dried1 a negative blue picture will be produced4 ,this picture ,i have found to be susceptible of a very curious transformation4 ,to effect this it must be washed with a solution of protonitrate of mercury1 which in a little time entirely discharges it4 ,the nitrate being thoroughly washed out and the picture dried1 a smooth iron is passed over it1 somewhat hotter than is used for ironing linen1 but not sufficiently so to scorch or injure the paper4 ,the obliterated picture immediately reappears1 not blue1 but brown4 ,if kept for some weeks in this state between the leaves of a portfolio1 in complete darkness1 it fades1 and at length almost disappears4 ,but what is very singular1 a fresh application of heat revives and restores it to its full intensity40 8,this curious transformation is instructive in another way4 ,it is not operated by light1 at least not by light alone4 ,a certain temperature must be attained1 and that temperature suffices in complete darkness4 ,nevertheless1 ,i find that on exposing to a very concentrated spectrum 7collected by a lens of short focus7 a slip of paper prepared as above 7that is to say1 by washing with the mixed solutions1 exposure to sunshine1 washing and discharging the uniform blue color so induced1 as in the last article71 its whiteness is changed to a brown over the whole region of the red and orange rays1 but not beyond the luminous spectrum4 ,three conclusions seem unavoidable3 first--that it is the heat of these rays1 not their light1 which operates the change2 second--that this heat possesses a peculiar chemical quality which is not possessed by the purely calorific rays outside of the visible spectrum1 though far more intense2 and third--that the heat radiated from obscurely hot iron abounds especially in rays analogous to those of the region of the spectrum above indicated40 ,sir ,john ,herschel then proceeds to show that whatever be the state of the iron in the double salts in question1 its reduction by blue light to the state of protoxide is indicated by many other agents4 8,thus1 for example10 says ,robert ,hunt1 8if a slip of paper prepared with the ammonio-citrate of iron be exposed partially to sunshine1 and then washed with the bichromate of potash1 the bichromate is deoxidized and precipitated upon the sunned portion1 just as it would be if directly exposed to the sun's rays40 8,i have proved this fact with a great number of preparations of cobalt1 nickel1 bismuth1 platinum and other salts which have been thought hitherto to be insensitive to the solar agency2 but if they are partially sunned and then washed with nitrate of silver and put aside in the dark1 the metallic silver is slowly reduced upon the sunned portion4 ,in many instances days were required to produce the visible picture2 and in one case paper being washed in the dark with neutral chloride of platinum was sunned and then washed in the dark with nitrate of silver2 it was some weeks before the image made its appearance1 but it was eventually perfectly developed1 and1 when quite so1 remained permanently impressed upon the paper40 ,the following process1 discovered at the same time as the cyanotype1 and termed chrysotype1 is thus described by ,sir ,john ,herschel3 8,in order to ascertain whether any portion of the iron in the double ammoniacal salt employed has really undergone deoxidation1 ,i had recourse to a solution of gold1 exactly neutralized by carbonate of soda4 ,the proto-salts of iron1 as is well known to chemists1 precipitate gold in the metallic state4 ,the effect proved exceedingly striking1 and1 as the experiment will probably be repeated by others1 ,i shall here describe it ab initio4 ,paper is to be washed with a moderately concentrated solution of ammonio-citrate of iron and dried4 ,the strength of solution should be such as to dry into a good yellow color1 not at all brown4 ,in this state it is ready to receive a photographic image1 which may be impressed on it either from nature in the camera obscura1 or from an engraving on a frame in sunshine4 ,the image so impressed is1 however1 very faint1 and sometimes hardly perceptible4 ,the moment it is removed from the frame or camera1 it must be washed over with a neutral solution of chloride of gold of such strength as to have about the color of a sherry wine4 ,instantly the picture appears1 not1 indeed1 at once of its full intensity1 but darkening with great rapidity up to a certain point1 depending on the strength of the solutions used1 etc4 ,at this point nothing can surpass the sharpness and perfection of detail of the resulting photograph4 ,to arrest this process and to fix the picture 7so far at least as the further agency of light is concerned71 it is to be thrown into water very slightly acidulated with sulphuric acid1 and well soaked1 dried1 washed with hydrobromate of potash1 rinsed and dried again4 99 99 990 8,in point of direct sensibility1 the chrysotype paper is certainly inferior to the calotype2 but it is one of the most remarkable peculiarities of gold as a photographic ingredient1 that extremely feeble impressions once made by light go on afterwards1 darkening spontaneously and very slowly1 apparently without limit so long as the least vestige of unreduced chloride of gold remains in the paper4 ,to illustrate this curious and 7so far as applications go7 highly important property1 ,i shall mention incidentally the results of some experiments made during the late fine weather on the habitudes of gold in presence of oxalic acid4 ,it is well known to chemists that this acid1 heated with solutions of gold1 precipitates the metal in its metallic state2 it is upon this property that ,berzelius has founded his determination of the atomic weight of gold4 ,light1 as well as heat1 also operates this precipitation2 but to render it effectual1 several conditions are necessary3--,first--the solution of gold should be neutral1 or at most very slightly acid2 secondly--the oxalic acid must be added in the form of a neutral oxalate2 and thirdly--it must be present in a certain considerable quantity1 which quantity must be greater the greater the amount of free acid present in the chloride4 ,under this condition1 the gold is precipitated by light as a black powder if the liquid be in any bulk2 and if merely washed over paper1 a stain is produced1 which1 however feeble at first1 under a certain dosage of the chloride1 oxalate and free acid1 goes on increasing from day to day and from week to week1 when laid by in the dark and especially in a damp atmosphere1 till it acquires almost the black of ink2 the unsunned portion of the paper remaining unaffected1 or so slightly as to render it almost certain that what little action of the kind exists is due to the effect of casual dispersed light incident in the preparation of the paper4 ,i have before me a specimen of paper so treated in which the effect of thirty seconds' exposure to sunshine was quite invisible at first1 and which is now of so intense a purple as may be well called black1 while the unsunned portion has acquired comparatively but a slight brown4 ,and 7what is not a little remarkable1 and indicates that in the time of exposure mentioned the maximum of effect was attained7 other portions of the same paper exposed in graduated progression for longer times1 viz41 one minute1 two minutes1 and three minutes1 are not in the least perceptible degree darker than the portion on which the light has acted during thirty seconds only40 8,if paper prepared as above recommended for the chrysotype1 either with the ammonio-citrate or ammonio-tartrate of iron1 and impressed1 as in that process1 with a latent picture1 be washed with nitrate of silver instead of a solution of gold1 a very sharp and beautiful picture is developed of great intensity4 ,its disclosure is not instantaneous2 a few moments elapse without apparent effect2 the dark shades are then first touched in1 and by degrees the details appear1 but much more slowly than in the case of gold4 ,in two or three minutes1 however1 the maximum of distinctness will not fail to be obtained4 ,the picture may be fixed by the hyposulphite of soda1 which alone1 ,i believe1 can be fully depended on for fixing argentic photographs40 8,the best process for fixing the photographs prepared with gold is as follows3 ,as soon as the picture is satisfactorily brought out by the auriferous liquid1 it is to be rinsed in spring water1 which must be three times renewed1 letting it remain in the third water five or ten minutes4 ,it is then to be blotted off and dried1 after which it is to be washed on both sides with a somewhat weak solution of hydriodate of potash4 ,if there be any free chloride of gold present in the pores of the paper it will be discolored1 the lights passing to a ruddy brown2 but they speedily whiten again spontaneously1 or at all events on throwing it 7after lying a minute or two7 into fresh water1 in which1 being again rinsed and dried1 it is now perfectly fixed40 ,as the chrysotype will be no more referred to1 we shall state1 first1 that the image can be developed with a plain solution of silver nitrate or one acidified with citric or any other organic acid1 which generally gives a brown impression that can be toned with an acid or alkaline gold bath1 the color varying with the solution employed2 and secondly1 that the process may be employed to obtain outlines of any picture on paper or canvas to be colored in oil-paints4 ,the impression developed with gold terchloride is pale blue1 quite permanent1 and does not at all interfere with the work of the artist4 ,the canvas should first be washed with a mixture of alcohol and aqueous ammonia1 then dried and rubbed with pumice stone powder to give a tooth4 ,the modus operandi suggests itself4 ,the researches of ,mr4 ,c4 ,j4 ,burnett on the application of uranium salts and other compounds to photography are recorded in the ,photographic ,notes of ,ths4 ,sutton for #aheg4 ,we give in the following lines the most interesting parts of the two papers of ,mr4 ,burnett3 99 99 99 8,the next class of processes are dependent on the sensitiveness to light of the salts of uranic oxide or sesquioxide of uranium1 ,u#b,o#c40 8,in the first process1 the paper being charged with the uranic salt and exposed to the solar influence under the negative to be copied1 is washed with a solution of the ferridcyanide or red prussiate of potash4 ,the #8,harvest ,scene' in the exhibition1 being from an albumen negative lent me by ,mr4 ,ross1 the well-known ,edinburgh photographer1 is an example1 the salt of the sesquioxide of uranium being in this case the hydrofluate1 and the time of exposure from the strength of the albumen negative fully an hour of good sunshine4 ,i have used for the solution of the uranic oxide for this process a variety of acids with very similar results2 the sensitiveness of the prepared paper to light varying much1 however4 ,for instance1 a collodion negative with the hydrofluate paper producing a very good print in half an hour of unsteady sun1 while with a paper prepared with the tartaric acid solution of the oxide1 it gave an equally good impression in less than five minutes of the same intermitting sunshine1 indicating thus a difference of sensitiveness of six to one in favor of the tartrate40 8,the rationale of this process is the reduction of the sesqui-oxide of uranium1 ,u#b,o#c1 on those parts of the paper exposed to the solar influence1 to a lower state of oxidation1 the photo-oxide ,,uo1 the salts of which have the property of forming with soluble alkaline ferridcyanides a rich chocolate-brown precipitate1 while the salts of the sesquioxide are destitute of this reaction4 ,hence the brown deposit on the parts of the picture on which the sun has been allowed to act when the developing solution is applied1 and the absence of any such appearance on those parts which have been protected from its influence40 8,as to the manipulatory details of this process1 the paper is floated on the solution in a dark room and hung up to dry1 and then preserved from light in a portfolio4 ,if carefully secluded from light it appears to keep well4 ,after exposure for the proper time under this negative1 there is in some cases scarcely any visible impression2 while in other cases1 particularly when using the tartaric solution1 ,i have found the impression very distinguishable1 of a brownish or blackish shade1 although still quite faint4 ,the development is best conducted by floating it1 anything like rubbing the picture being very objectionable40 8,when the picture has fully come out1 which is generally from three to ten minutes at the very most1 it is removed from the developing bath1 placed in cold water and washed very gently for a few minutes1 the water being frequently changed till it ceases to acquire a yellow tinge from the dissolved red prussiate4 ,the picture is then drained from the water1 pressed between folds of blotting paper1 dried 7,i dry in the dark71 and the process is complete4 99 99 99 ,i may state1 as one recommendation of this process to ladies and other lovers of clean hands1 that any brown stains left by it on the fingers or elsewhere are at once removable by a little weak ammonia or soap and water4 99 99 99 ,i would particularly suggest1 as deserving of notice1 the development of the salts of sesquioxide of uranium1 and still more iron1 by the metals and metallic-cyanic alkaline salts1 as also by the mellonides and nitro-prussides1 and the latter also by itself and as developed by many metallic salts40 8,i have since had the opportunity of trying the nitro-prusside of sodium1 which1 by itself1 gives a blue and white picture1 in color like that obtained from the red prussiate of potash40 8,when mixed with a solution of ammonio-nitrate of copper1 previous to its application to the paper1 the color obtained is pale purplish pink or peach-blossom color4 ,by mixing it in the same way with ammonio-oxalate of sesquioxide of iron1 we get a dull green picture1 changeable through intermediate stages into brown by alkaline carbonates1 and that into a dirty black by gallic acid4 ,it may be well to know that the blue of the picture given by the red prussiate in the process of ,sir ,john ,herschel may be considerably modified or entirely changed to another color1 in many ways1 without interfering with the purity of the white ground1 by steeping the picture1 after the undecomposed red prussiate has been washed out1 in solution of salts of various metals1 copper1 uranium or cobalt1 for instance1 and that the colors so produced may be modified as desired1 according to the stage at which the action is stopped40 8,there remains but one class of uranic photographs to be described1 namely1 that obtained when we develop with a salt of silver or gold 7or platinum874 ,this class may be made to print much more rapidly than our ordinary silver printing process1 approaching sometimes more nearly to the calotype development in this respect4 ,we get the minutest details with great fidelity1 and the picture is effectually fixed by a simple fresh hyposulphite solution1 with a good color in many cases1 or by ammonia1 which will be considered an advantage by those who hold the hyposulphite an enemy to durability4 ,different shades of color are produced according to different solvent acids and different details4 ,i have got a good black perfectly like that of an engraving1 by the nitrate of uranic oxide1 developed by ammonio-nitrate of silver 7or plain nitrate7 and fixed by plain hyposulphite without any coloring bath4 99 99 99 ,i have tried the hyposulphite of gold on some of the silver-developed prints prepared with the hydrofluate of the uranic oxide and fixed with ammonia1 which had an exceedingly unpleasant raw-red color1 a very agreeable gray was at once obtained4 ,i have succeeded in getting very beautiful impressions by development of the uranic paper by chloride of gold alone40 ,in another communication to the ,photographic ,notes1 more interesting perhaps than the foregoing1 ,mr4 ,burnett says3 8,the clearest and brightest of my results have been obtained by the action of gallic acid1 tannin1 or especially a mixture of tannin and carbonate of ammonia1 potash or soda1 on the blue pictures obtained by the solarization of paper prepared with ferridcyanide of potassium1 ferrocyanide or ferridcyanide of ammonium4 99 99 99 ,i have also experimented with the bichromate and iron1 with gallic1 tannin and other developer2 but ,i must confess to not having been1 in this particular way1 so successful as ,mr4 ,sella appears to have been in the preservation of the whites1 owing possibly to my not having taken the trouble to wash out sufficiently the iron before toning407#a7 8,i have experimented most extensively in many ways with the chromates and bichromates1 and have succeeded in various ways in getting very good results4 ,a very capital process for many purposes is to float or steep your paper in a mixed solution of bichromate of potash and sulphate of copper4 ,as for ,e4 ,hunt's chromotype process10 7#b7 ,i have mixed gelatine1 or occasionally grape sugar1 or both1 with the solution1 but instead of developing it by a silver solution1 as in the chromotype1 wash out the salts unacted on by light1 and develop by floating on a solution of ferrocyanide of potassium4 ,the color of the red copper salt which now forms the picture may be modified or changed in many ways1 viz41 by soaking the picture1 after the ferrocyanide of potassium has been washed out of the lights1 in a solution of sulphate of iron 7or the iron salt may1 but not so advantageously1 have been applied to the picture before the application of the ferrocyanide74 ,solutions of chloride of tin1 gallic and tannic acids1 alone or with alkalies or alkaline carbonates1 may also be employed to modify or change the color4 ,instead of developing by ferrocyanide you may develop by the cobalt or chromo-cyanogen salts1 or by an alkaline mellonide arsenite1 etc4 ,sulphureted hydrogen1 or a sulphide1 will give a brown1 or black tone1 which may be protected against oxygen and dampness by a resinous varnish4 8,of all the simple pictures obtainable with bichromated papers1 without complications or other tonings1 those obtainable by the combination of a salt 7say the sulphate7 of manganese1 with the bichromate in the paper preparation1 are about the best2 these pictures being1 however1 capable of being toned and modified in many different ways if desired4 ,this may be accomplished by the use of toning baths of ferridcyanide or ferrocyanide1 or other metal cyanogen salts1 etc41 or by either mixing the salts of other metals1 as copper or iron1 with the cyanic toning baths1 or using them in the original solution1 or by soaking the paper in them1 as in ,sella's process1 previously to the application of the metal cyanic1 mellonic or other toning baths4 ,alkalies and alkaline carbonates may also be used to remove the chromic acid1 and leave a subsalt1 or the very stable oxide or carbonate of manganese1 which may be peroxidized by the use of chloride of lime1 peroxide of hydrogen1 or ozone40 8,in all the processes with metallic salts1 alone with bichromates1 the use of sized or unsized paper along with gelatine1 etc41 has some advantages4 ,i have got good results by such processes on albumen paper1 the albumen tending to prevent mealiness in the print2 also on paper soaked in gelatine before the application of the bichromic solution4 99 99 99 ,there is great interest connected with the action of all such papers1 along with the tannin and vegetable coloring matters4 ,i have long been of opinion that by the steeping of papers or textile fabrics1 containing the salts not only of iron1 as recommended by ,mr4 ,sella1 but of tin1 copper1 bismuth1 lead1 etc41 in solutions of cochineal1 red cabbage1 beetroot1 grass or the most ordinary foliage1 etc41 that the most useful results might be obtained2 though for certain permanence ,i am not sure but that some of the other processes which ,i have briefly run over with the cyanogen acid salts or metallic acid salts1 as precipitators1 may be more to be depended upon4 ,the processes with precipitated oxides1 such as the one with manganese and similar ones1 with other metals which ,i have described1 ,i also consider as deserving of more attention than almost any processes which have been stated1 on the score of probable permanence2 but perhaps the best process for black1 or generally useful neutral tint1 without silver1 that has yet been offered to the public1 ,i believe to be the process alluded to with the bichromate of potash and sulphate of copper1 toned by an iron salt4 99 99 99 ,this process1 the cuprotype 7as also the uranotype and manganotype7 is applicable perfectly to films of albumen or gelatine on glass or porcelain1 textile fabrics1 parchment1 paper1 tiles and many other substances besides paper40 ,,the ,,designs4 ,,how ,,to ,,make ,a ,,negative ,,drawing ,the drawing paper for designs to be reproduced by the cyantotype and the other processes described in this book should be of a fine texture1 free from opacities and very white2 and1 as the design must serve as a clich it is a sine qua non that it be drawn with a very black ink and with well-fed lines1 especially those which are very fine4 ,to obtain a complete opacity1 and1 at the same time1 to keep the ink quite fluid1 which gives great facility to the designer1 one adds some gamboge 7or burnt sienna7 to the ,india ink4 ,the ink of ,bourgeois1 which is compounded with yellow and can be diluted as easily as ,india ink1 is excellent1 so is also the ,american ink of ,higgins47#c7 ,as much as possible it is desirable to replace the colored lines indicating the constructions1 the axis1 projections1 etc41 by differently punctuated lines made with ,india ink4 ,however1 if the use of colors be obligatory on the original design1 one should trace the red lines with very thick vermilion or sienna1 the yellow lines with gamboge1 and the blue and green lines with a thick mixture of ,prussian blue and chrome yellow in different proportions4 ,one must abstain from applying washes of any tints on the original4 ,if necessary they should be brushed over when the reproductions are made2 moreover they can be often replaced by cross-lines more or less open1 and the shadowing represented by thicker but not closer lines4 ,tracing paper is recommended instead of linen1 which latter1 on account of its thickness and granulation1 gives less satisfactory results in regard to the transparency of the ground and the continuity of the lines4 ,to reproduce a design on ordinary paper--not too thick--or an engraving1 etc41 the paper is rendered transparent by rubbing over on the back of the original a solution of #c parts in volume of castor oil in #aj parts of alcohol1 by means of a small sponge4 ,when the paper is quite transparent1 the oil in excess is removed by pressure between sheets of blotting paper1 and the paper dried before the fire or spontaneously4 ,the design so treated is not in the least injured1 for it assumes its primitive condition by dissolving the oil from the paper by immersion into strong alcohol1 which it is necessary to renew once or twice1 then rinsing in alcoholized water if the drawing be in ,india ink1 or simply in water in the case of an engraving1 and finally drying between sheets of blotting paper4 ,instead of an alcoholic solution of castor oil1 vaseline can be employed4 ,the paper is more transparent4 ,the method by which are made negative drawings1 that is1 those which can be used as negative clichs to reproduce the design in black lines on a white ground1 is thus described by ,mr4 ,cheysson1 wlio originated it1 in a manual published by the ,department of ,public ,works of ,france1 from which we have borrowed most of the above instructions for the drawing of designs suitable for the photo-reproduction processes37#d7 8,one can avoid the necessity of making a negative from the original drawing by transforming the drawing itself into a negative40 8,to that effect it suffices to draw with lithographic ink1 then to cover the paper with aniline brown1 and1 after drying1 to wash it with turpentine oil which dissolves the lithographic ink without altering the aniline4 ,the lines appear then white on a brown ground impervious to light 7that is1 non-actinic74 ,the design is thus transformed into a negative1 and can yield positive impressions with paper sensitized with silver salts1 the ferriprussiate or the bichromate of potash4 ,the lithographic ink should be very black and the lines well fed40 8,when the drawing is finished it is placed on a board lined with sheets of blotting paper1 then one spreads all over it the aniline brown with a brush1 and1 lastly1 after drying1 the paper is carefully rubbed with a bung of cotton or a rag imbued with turpentine until the lines of the design are dissolved40 ,in our practice we have often taken a negative clich from drawings made in the ordinary manner1 without the aid of the camera obscura 7which would have been too expensive for drawings of a certain size71 by simply printing a proof by contact on plain or albumenized silvered paper1 and fixing1 without toning1 in a new solution of sodium thiosulphate1 then washing as usual4 ,the proofs thus obtained from designs drawn with an opaque ink1 which allows a long insulation and1 therefore1 yields an intense reduction1 are of a deep brick-red color1 quite non-actinic1 and give very good positives by the ,artigues process4 ,n4,b4--,paper in drying never assumes its original shape2 it is1 therefore1 necessary to make the figures on the reproductions from plans when they are not on the originals4 ,,choice ,,of ,,paper4 ,,sizing4 ,in all the photographic processes by precipitation of metallic oxides the quality of the paper has a great influence on the results4 ,when the paper is not well sized and not well calendered1 the sensitizing solution is absorbed1 instead of simply impregnating the surface of the paper1 and not only the image is sunk in and its sharpness impaired1 but good whites can never be obtained1 especially if the image should be toned1 owing to the impossibility of eliminating the metallic salts not acted on1 that is1 not reduced by the action of light which the fibers of the paper mechanically retain4 ,the 8endless0 rolls of paper1 #ed3 inches wide--or 8blue print paper10 as it is sometimes termed--of ,blanchet frres et ,klber1 of ,rives1 better known as 8,rives' paper01 that of ,johannot1 of ,annonay 7,france71 and the ,steinbach 7,saxe7 paper are recommended4 ,for small prints from negatives in half tone the positive paper1 #ahbb inches1 of ,rives or ,saxe1 should be preferred to the heavy kind4 ,it is advisable to size it1 so that the impressions be entirely formed on the surface of the paper4 ,moreover1 an additional sizing is always advantageous1 whatever be the photographic process employed1 to prevent the imbibition of the sensitizing compound and to obtain more brilliant and vigorous images1 for the iron1 chromium1 uranium and other metallic soluble salts require the presence of an organic matter 7alcohol1 ether1 gum arabic1 glucose1 caseine1 etc47 to be reduced by the agency of light2 and as a consequence1 the greater1 within certain limits1 of course1 the amount of organic matters1 and the more thoroughly they are mixed with the salts1 the more sensitive the preparation and the better the results4 ,arrowroot is the best sizing for our purposes4 ,gelatine may be employed1 albumen also1 but the coating should be insolubized when applied on the paper and dry4 ,sizing with ,arrowroot4--,in a porcelain dish diffuse #d parts of powdered arrowroot and one part of liquid glucose in #bjj parts of distilled or rain water and dissolve by heat over an alcohol lamp1 stirring all the while4 ,let the solution boil for an instant1 and when the paste is homogeneous let it cool down and then remove the skin formed on its surface and strain it through a fine canvas4 ,now provide with three small sponges free from gritty matters and cleaned in water1 and nail by the four corners1 one over the other1 felt size uppermost1 as many sheets of paper as you wish to size on a board somewhat smaller than the paper4 ,this done1 with one of the sponges take a small quantity of the arrowroot and1 brushing it length-way and cross-way1 spread the paste into an even layer1 then1 by rubbing very lightly with the second sponge1 efface the striae and smooth the coating as well as possible4 ,the third sponge serves to remove the excess of paste when too much is at first spread on4 ,from six to seven sheets of paper1 #ahbb1 can be sized with the quantity of arrowroot paste above given4 ,another1 but not quite so effective a manner of sizing although sufficient for the cyanotype1 is the following1 employed by ,mr4 ,pizzighelli for the paper used in the platinotypic process3 ,ten parts of arrowroot are powdered in a mortar with a little water and then mixed by small quantities to #hjj parts of boiling water4 ,after a few minutes #bjj parts of alcohol are added and the mixture filtered4 ,the paper is immersed for two or three minutes in the warm solution and hung up to dry4 ,sizing1 with ,gelatine4--,dissolve at a temperature of about #adj deg4 ,fahr4 7#fj deg4 ,c47 #aj parts of good gelatine in #hjj parts of water1 then add #bjj parts of alcohol and #c parts of alum dissolved in a little water4 ,filter and prepare the paper by immersion as above directed4 ,the gelatinized paper when dry should be prepared a second time and dried by hanging it up in the opposite direction in order to obtain an even coating4 ,,the ,,cyanotype ,,or ,,blue ,,process4 ,this process gives white impressions on a blue ground with diapositives or drawings on transparent or semi-transparent materials1 and blue impressions on a white ground from negatives4 ,it is commonly known under the names of 8blue print process10 8negative ferrotype process0 and 8ferro-prussiate process40 ,the process is indeed exceedingly simple4 ,a sheet of paper1 impregnated or sensitized1 as it is termed1 with a solution of ferric citrate and ferricyanate is impressed under a clich17#e7 then immersed in pure water1 whereby the image is developed and at the same time fixed4 ,it is on account of the great advantages offered by its simplicity that this process is generally preferred by civil engineers and architects for the reproduction of their plans4 ,the sensitizing solution is prepared in mixing by equal volumes the two solutions following3 ,a4 ,iron1 ammonio #bj parts citrate ,water #ajj parts ,b4 ,potassium #ae parts ferricyanate 7red prussiate7 ,water #ajj parts ,although the mixture keeps pretty well for a certain period in the dark1 it is best to prepare only the quantity wanted for actual use47#f7 ,the paper is preferably sensitized in operating as follows3 ,take hold of the paper by the two opposite corners and fold it into a loop1 lay it on the iron solution1 the center of the sheet first placed in contact with the liquid1 and then gradually spread it by lowering the corners with a little pressure4 ,no solution should run over on the back of the paper2 it would be a cause of stain4 ,this done1 and without allowing the liquid to penetrate in the paper1 immediately take hold of the two corners near the body and withdraw the paper by dragging it over on a glass rod for this purpose fixed on the edge of the tray4 ,now pin up the paper to dry1 which should be done rapidly1 and sensitize a second time in proceeding in the same manner4 ,if this second sensitizing be found objectionable1 let float the paper for no more than ten seconds2 of course this method of sensitizing is not applicable to prepare larger sheets of paper4 ,in this case the paper is pinned by the four corners on a drawing board or any other support1 lined with blotting paper and quickly brushed over with a sponge sparingly imbued with the sensitizing mixture1 so as to wet the paper with a very small excess of liquid4 ,the rationale of this manner of sensitizing is to impregnate only the very surface of the paper with the ferric salts1 and thereby to obtain an intense blue with very good whites1 which latter it would be impossible of obtaining should the sensitizing solution be allowed to reach in the fibers of the paper1 for1 in this condition1 it is impossible1 owing to the exigencies of the process1 to wash out thoroughly the iron salts to prevent the chemical changes which cause the whites to be tinted blue4 ,it is for this reason that better results are also obtained with well sized papers4 ,the sensitizing should be done by a very diffused daylight1 and the drying1 of course1 in a dark room4 ,when sensitized the paper is yellowish green4 ,it should be well dried for keeping1 and rolled or wrapped in orange or brown paper and preserved from the action of dampness and of the air4 ,it does not keep well1 however1 no more than two or three months1 perhaps1 in good condition2 but the sooner it is employed the finer the proofs1 the better the whites and more rapidly is the paper impressed4 ,there is in the market a paper which keeps for a long time4 ,it is prepared by adding a small quantity of gum arabic or of dextrine to the sensitizing solution4 ,good for the reproduction of line work1 it does not give very satisfactory results for pictures in half tones4 ,the following compound gives a paper much more sensitive1 but not keeping so long1 than that prepared according to the formula previously given3 ,tartaric acid #be parts ,ferric chloride1 solution #hj parts 7in volume7 at #de deg4 ,baum ,water #ajj parts ,when the acid is dissolved1 add gradually concentrated aqueous ammonia1 just enough to neutralize the solution--#agj volumes1 about4 ,the chemical change consists in the formation of ferric tartrate4 ,let cool the solution1 then1 after adding the following1 keep it in the dark3 ,potassium ferricyanate #ba parts ,water #ajj parts ,another and very sensitive preparation is the following3 ,a4 ,iron perchloride1 #dj parts cryst ,oxalic acid #aj parts ,water #ajj parts ,b4 ,potassium #bj parts ferricyanate ,water #ajj parts ,mix ,printing4--,the process we describe yields negative impressions1 that is a positive image from a negative clich1 and a negative image from a positive clich1 exactly as the silver printing-out process ordinarily employed in photography4 ,consequently1 for the production of non-reversed proofs from plans1 etc41 the original drawing should be placed face downwards on the glass plate of the printing frame1 and1 upon the back1 the sensitive paper is laid and pressed into perfect contact by means of a pad1 felt or thick cloth4 ,the printing frame is that used by photographers4 ,the lid is divided1 according to the side1 in two1 three and even four sections1 held by hinges and fastened for printing by as many cross-bars1 in order that by opening one section1 from time to time1 the operator can follow the progressive changes resulting from the action of light on the iron salts4 ,to print1 the frame should be placed in the light in such a manner as the luminous rays fall perpendicularly upon the drawing or clich4 ,the reason of this is obvious1 since the sensitive paper is not in direct contact with the design1 but separated by the material upon which it is drawn4 ,during the insolation--whose time depends necessarily from the more or less transparency of the clich1 and1 also1 from the intensity of the light7#g7--the paper assumes first a violet tint1 which gradually intensifies to a dark shade2 then this tint fades1 becomes brownish1 then pale lilac1 while the parts under the lines--that is1 the design--upon which the light has1 therefore1 no action1 are visible by keeping the original yellow-green tint of the prepared paper4 ,it is when the lilac color is produced that the exposure is sufficient4 ,to ascertain when the exposure is correct1 a few black lines can be traced on one of the edges of the margin of the design1 and strips of the sensitive paper placed upon them to serve as tests in operating1 as it will be explained in the description of the ,cyanofer process4 ,when one of them is taken out and show1 by being washed in water1 a clear white line on a deep blue ground1 the exposure is at an end4 ,one understands that the blue color of the ground is more or less intense according to time of insolation1 for the chemical actions between the reduced and the non-reduced iron salts is so much more complete as the salts acted on are more or less deoxidized1 that is1 reduced to ferrous salts2 and that to obtain the maximum of effect1 which1 therefore1 depends on the allowable time of exposure1 the drawing ink should be opaque and non-actinic as far as possible1 because when1 on testing1 the lines are tinted the exposure should be discontinued4 ,however1 a slight coloration of the lines is not very objectionable1 for it disappears by a longer washing after the development4 ,the image is developed and fixed by washing in water two or three times renewed4 ,the water must be free from calcareous salts2 these salts converting the iron into carbonates which impart an ochrey tinge to the proof4 ,rain water--any water in which no precipitate is thrown down by the addition of a few drops of a weak solution of silver nitrate--may be used with safety4 ,during the development the ground takes a blue color which rapidly intensifies1 while the iron compound1 not acted on and imparting a yellow green tint to the design1 is washed out from the white paper4 ,if the print has not been sufficiently exposed the ground remains pale blue1 more or less2 the reason has been explained4 ,in this case the development should be done quickly1 as the blue is always discharged by washing4 ,on the other hand1 whenever the whites are tinted by excess of exposure1 they can be cleared partly or entirely by a prolonged immersion in water1 but the ground is also to some extent lightened4 ,when the proof is well developed and fixed1 that is1 when the soluble iron salts are eliminated1 the blue color can be brightened by adding to the last but one washing water a small quantity of citric acid1 or of potassium bisulphate1 or a little of a solution of hypochlorite of lime 7bleaching powder74 ,the action of light in this1 as well as in the other photographic processes with metallic salts described in this work1 is one of deoxidation1 as shown by ,herschel4 ,the chemical changes which produce the blue precipitate is quite complicated4 ,it is evident that both the ferric citrate and the ferric cyanate are partly reduced to ferrous salts under the luminous influence1 and react in presence of water with the unreduced part of each of these compounds1 the ferric citrate with the ferrous cyanate forming ,prussian blue 7ferric-ferrocyanate71 and the ferric cyanate with the ferrous citrate giving rise to ,turnbull's blue 7ferrous ferricyanate74 ,the blue of the print is consequently a mixture in a certain proportion of the two compounds2 and as the color of ,prussian blue is quite different from that of ,turnbull's1 it follows that by varying in a certain measure the percentage of the two ferric salts forming the sensitizing solution1 the color of the blue may be varied thereby4 ,hence the difference in the formulas given by different authors47#h7 ,the blue color of the image can be changed into black or dark green4 ,but to that purpose the paper should be1 although not exactly necessary1 well sized as before directed1 and sensitized with extra care to prevent the imbibition of the iron solution into the paper4 ,after exposure the proof should necessarily be thoroughly washed to eliminate the soluble iron salts1 then immersed for a moment in water acidified with nitric acid1 #a3ajj1 and this done and without washing treated by a solution of aqueous ammonia at #b per #ajj of water4 ,in this the blue color disappears1 being changed into a red brownish tint1 which indicates that the ,turnbull's and ,prussian blues are transformed1 the former into ferroso-ferric hydrate1 with formation of ferrocyanate1 and the latter into ferric hydrate4 ,it is by the action of tannin 7gallotannic acid7 on the ferric oxides thus formed that the black is produced1 and by that of catechu-tannic acid contained in the extract of catechu that one obtains a dark green1 almost black color4 ,to obtain the black tone it suffices to immerse the proof on its removal from the ammoniacal in a solution of tannin at #e per #ajj of water1 and when toned1 to wash it in a few changes of water4 ,the process to turn the blue color into a green was devised by ,mr4 ,paul ,roy4 ,it is as follows3 ,dissolve #g parts of borax in #ajj parts of water1 and acidify the solution with sulphuric acid added drop by drop until the litmus paper becomes red2 then1 in the same manner1 neutralize with aqueous ammonia not in excess1 but just enough to show an alkaline reaction2 this done dissolve #a part of powdered catechu and filter4 ,in this the proof is immersed after development until the desired effect is attained4 ,wash1 etc4 ,to clear the lines1 or to make additions1 or to write on the blue margin of the proof a solution of potassium oxalate is employed4 ,it dissolves the blue without leaving scarcely any trace of it4 ,the solution can be prepared by mixing the two solutions whose formula is given below37#i7 ,a4 ,oxalic acid #aj parts ,water #ajj parts ,b4 ,caustic potassa #ab parts ,water #ajj parts ,the blue prints are permanent4 ,when drying they darken a little from oxidation2 exposed to sunshine for some hours1 they bleach considerably2 but in the shade the faded pictures progressively absorb oxygen from the air and assume their original intensity and color in a period so much the longer as the insulation has been more prolonged2 it may take weeks if the picture were much bleached4 ,,the ,,cyanofer4 7,,pellet',s ,,process47 ,this process gives blue impressions on a white ground from positive clichs1 and white impressions on a blue ground from negative clichs4 ,it is termed 8positive ferrotype process40 ,the cyanofer is an application of one of the numerous and useful inventions for which photography is indebted to ,a4 ,poitevin4 ,in #ahfc he discovered that certain organic substances were rendered insoluble by ferric chloride1 and that they again became soluble2 when under the influence of light the ferric chloride has been reduced to a ferrous salt4 ,this curious phenomenon is the base of the process now to be described4 ,as usual the process has been modified by compounding the sensitive solution in various ways and by minor details in the manner operating4 ,but although these modifications have rendered the process easier to work with1 there is not a great difference in the results obtained4 ,we give two formulas4 ,aside from the addition of gum arabic1 which was suggested by ,mr4 ,pellet1 and which constitutes the capital improvement of the process1 the formula is substantially that devised by ,mr4 ,poitevin4 ,prepare three solutions as follows3 ,a4 ,gum arabic1 best #ej parts quality ,water #agj parts ,b4 ,tartaric acid #ab parts ,water #hj parts ,c4 ,ferric chloride #ce parts in volume solution at #de deg4 ,baum ,mix gradually ,b to ,c1 then ,c1 by small quantities1 in agitating briskly4 ,it is important to prepare the solution as directed1 for by adding the ferric chloride before tartaric acid1 the gum arabic would be at once coagulated4 ,when the ferric chloride is mixed1 the solution at first thickens1 but becomes sufficiently fluid for use in a certain period4 ,it does not keep1 and should be employed the day it is made if possible4 ,the paper1 which should be well sized and calendered1 and which1 when not giving good results by too much absorbing the sensitive solution1 must be starched as before directed1 is coated either by brushing or by floating4 ,by the first method a roll of paper five yards long can be prepared without great trouble1 and give1 perhaps1 better results than if prepared by floating2 but the latter method is by far the the most convenient3 one does not generally prepare by brushing sheets of paper larger than about #cjdj inches4 ,for brushing1 the paper is pinned on a board1 then1 with a large badger brush dipped in the sensitive solution1 the latter is applied as evenly as possible2 after which1 by lightly passing the brush over1 the striae are removed1 the coating well equalized1 and the paper hung up to dry4 ,the coating should not be very thin1 and1 above all1 not too thick1 for then it would require an unusually long exposure to allow the light acting through the whole thickness of the film1 which is a sine qua non to obtain a clear ground1 i4e41 not stained blue4 ,to prepare by floating1 pour the solution in a shallow tray1 which needs not to be more than #bjcd inches1 #cj inches being the width of the drawing paper usually employed2 then roll the paper and place it on the solution4 ,now1 taking hold of it by two corners1 draw it out slowly3 the paper will unroll by itself4 ,this operation can be done by diffused daylight1 but1 of course1 the paper should be dried in a dark room4 ,it dries rapidly4 ,endless rolls are prepared by machinery4 ,to expose1 the drawing is placed in the printing frame1 face downwards1 and the sensitive paper laid over it4 ,the whole is then pressed into contact by interposing a cushion between the lid of the frame and the paper1 and exposed so that the rays of light fall perpendicularly upon it4 ,the cyanofer preparation is quite sensitive4 ,from half a minute to two minutes exposure1 according to the intensity of the light and the thickness of the coating1 is sufficient in sunshine to reproduce a drawing made on the ordinary tracing paper4 ,in the shade1 by a clear sky1 the exposure is about five times longer1 and varies from half an hour to an hour and more in cloudy weather1 but then the design is seldom perfectly sharp4 ,the progresses of the impression is followed by opening one side of the printing frame and examining the proof4 ,the exposure is sufficient when the paper is tinged brown on the parts corresponding to the ground of the design4 ,the image appears then negative1 that is1 yellowish on a tinged ground4 ,another and more safe method of ascertaining the correct time of exposure1 which can be employed concurrently with the other1 is to place a few strips of the same sheet of sensitive paper between the margin of the design1 upon which a few lines have been traced1 and the paper1 and1 without opening the frame1 to draw one of them1 from time to time1 and dip it in the developing solution4 ,if the whole strip be tinted blue1 the proof is not sufficiently exposed2 but if the lines soon appear with an intense coloration on the yellowish ground of the paper1 and the latter do not turn blue in a minute1 at the most1 the exposure is right4 ,by excess1 the lines are with difficulty developed or broken4 ,for developing1 we provide with three wooden trays lined with lead or gutta-percha1 or1 more economically1 coated with yellow wax4 ,the wax is melted1 then applied very hot1 and1 when it is solidified and quite cold1 the coating is equalized with a hot iron1 whereby the cracks produced by the contraction of the wax when cooling are filled up4 ,one of these trays should contain a layer1 about three-quarters of an inch thick1 of an almost saturated solution of potassium ferrocyanate 7the developer72 the next be filled with water1 and the third with water acidified by sulphuric acid in the proportion of three per cent4 in volumes4 ,all this being ready1 the margin of the proof is turned upwards--so as to form a disk of which the outside is the impressed surface--in order that the ferrocyanate solution does not find its way on the back of the proof1 which would produce stains4 ,now the proof is laid1 the lower edge first1 on the developer1 and gradually lowered upon it1 when1 taking immediately hold of it by the two corners nearest to the body1 it is lifted out and held upright to allow one following the development of the image2 and1 presently1 if any air-bubbles are seen on the proof1 they should at once be touched up with a brush wetted with the ferrocyanate solution2 the reason explains itself4 ,the image appears at once4 ,as soon as the fine lines are well defined1 the blue intense1 and1 especially1 when the ground has a tendency to be tinged blue1 the proof is placed in the tray filled with water and in this turned over two or three times1 when it is immersed in the diluted sulphuric acid4 ,in this bath the print acquires a deep blue coloration1 consisting of ,prussian blue1 and the ground becomes tinted with a blue precipitate without adherence1 which is easily washed off by throwing the liquid on the proof with a wooden spatula1 or1 better1 by rubbing with a rag tied to a stick4 ,when the ground is cleared1 and after three or four minutes immersion to dissolve the iron salts acted on1 the proof is rinsed in water several times renewed to free it from acid1 and hung to dry4 ,there are two causes of failures in this process1 viz41 over and under-exposure4 ,in the former case the fine lines are broken or washed out in clearing the proof 7which may also arise from the drawing made with an ink not opaque enough72 in the latter the ground is more or less stained4 ,the blue stains1 the lines for corrections1 etc41 are erased with the the potassic oxalate 7blue salving1 as it is termed7 whose formula has been given4 ,the additions1 corrections and writing are made with a ,prussian blue ink prepared by mixing the two following solutions3 ,a4 ,ferric chloride1 #d parts dry ,water #cej parts ,b4 ,potassium #ae parts ferrocyanate ,water #bej parts ,the precipitate being collected on a filter and washed until the water commences to be tinged blue1 is dissolved to the proper consistency in about #djj parts of water4 ,this ink does not corrode steel pens4 ,it has been stated that the cyanofer process keeps for years if preserved from the combined action of dampness and the air4 ,the writer found in his practice that the ferric salts in presence of the organic matters 7the sizes7 acts as does potassium bichromate and renders1 in a certain period1 the cyanofer film insoluble even after a prolonged insulation4 ,paper freshly prepared is always more sensitive and gives better whites and generally finer results47#aj7 ,the prints can be toned black in operating as in the cyonotype1 but the results are seldom good4 ,captain ,pizzighelli's formula is as follows3 ,prepare ,a4 ,gum arabic #ae parts ,water #ajj parts ,b4 ,ammonia ferric #de parts citrate ,water #ajj parts ,c4 ,ferric chloride #de parts ,water #ajj parts ,for sensitizing mix in order3 ,solution ,a #ajj parts ,solution ,b #dj parts ,solution ,c #bj parts ,the mixture very much thickens at first1 but becomes sufficiently fluid for use in a few hours4 ,it keeps well for two or three days4 ,leaving out ,b and replacing it by rain water1 this makes also a good solution for the cyanotype4 ,,the ,,black ,,or ,,ink ,,process4 7,,ferro-,,tannate ,,process47 ,this process gives black positive impressions on white ground from positive clichs1 and negative impressions from negative clichs4 ,it has been attributed to ,mr4 ,colas1 but in reality it was invented by ,mr4 ,poitevin1 who describes it as follows in his communication of ,may1 #ahfj1 to the ,socit ,francaise de ,photographie3 8,i make a solution containing--0 ,iron perchloride1 cryst #aj parts ,tartaric acid #c parts ,water #ajj parts 8,i apply the paper on this mixture and let it dry spontaneously in the dark1 and at the moment of using it ,i completely desiccate it at a gentle heat4 ,thus prepared the paper is of a deep yellow color4 ,light decolors it rapidly1 and ten or twelve minutes' exposure through a positive clich suffices to well impress it1 that is1 to reduce in the whites the iron perchloride to the state of protochloride40 8,to print1 one is guided by the decoloration of the paper1 and even for more facility ,i add to the solution of iron perchloride and tartaric acid a small quantity of a solution of potassium sulphocyanide for the purpose of obtaining a red tint1 which is more visible and disappears also under the influence of light in proportion to the decomposition of the perchloride4 ,one obtains then after exposure a red design on the white ground of the paper4 ,this red color is not permanent4 ,it even disappears by keeping the proof in the dark40 8,to develop and then to fix the design thus obtained ,i wash rapidly the paper in ordinary water1 or better1 in water holding chalk in suspension4 ,the red coloration disappears1 a part of the iron perchloride is washed out1 and in the parts which have not been acted on by light the perchloride is transformed into sesquioxide4 ,i replace then the water by solution of gallic acid or of tannin and the image progressively appears in ink-black4 ,when ,i judge the image to be sufficiently intense ,i wash the proof in rain water1 in preference to ordinary water1 which might cause the gallic acid and tannin to turn brown4 ,i sponge between sheets of blotting paper and let the proof dry spontaneously40 8,if in place of gallic acid ,i use a diluted solution of potassium ferricyanide 7red prussiate of potash71 ,prussian blue is formed in the parts acted on by light4 ,the preparation is even sensitive enough to permit one to obtain an impression in the camera obscura in developing by the ferricyanide40 8,as to the proofs in gallate 7or tannate7 of iron1 they can be transformed into ,prussian blue in a solution of potassium ferrocyanide 7yellow prussiate of potash7 slightly acidified by sulphuric acid40 ,the paper most suitable for this process is that which has been previously well sized with starch1 as explained in a special paragraph of this pamphlet4 ,paper prepared with a film of coagulated albumen gives also good results4 ,it may be prepared by brushing as well as by floating1 but in either case the paper should be wetted on the surface only and dried rapidly at a temperature of about #aae deg4 ,fahr4 7#df deg4 ,c47 and kept in a dry place4 ,it does not keep for more than from ten to fifteen days1 owing to the hygroscopicity of the iron compound4 ,mr4 ,colas1 who prepares the paper for the ,parisian market1 ,i think1 states that he avoids its deterioration by keeping it wrapped in blotting paper1 between two sheets of ,india rubber1 to exclude air and dampness4 ,silvered albumen and plain paper1 well desiccated1 could be kept in that way for a certain period1 especially if the blotting paper is impregnated with sodium bicarbonate and well dried4 ,mr4 ,a4 ,fisch advises to discard the preliminary washing and to develop just on the removal of the proofs from the printing frame4 ,in operating in this manner the development is best made by floating1 taking care that the solution does not run off the back of the proof4 ,the developer may consist of a dilute solution of nutgalls or of ,tannin or gallic acid #d parts ,oxalic acid #j4ae parts ,water #a1jjj parts ,after developing the proof should be washed rapidly--under a jet of water1 if possible--for were the iron salt and the reagent not soon removed1 or any remain in the paper1 the ground would be tinted violet4 ,and whatever be the care taken1 it very seldom occurs that the whites are pure when the proof is dry4 ,this for half-tone pictures has not a great importance1 but for the reproductions of plans it is sometimes objectionable4 ,in fact it must be acknowledged that none of the processes now at our disposal--if we except the so-called ,artigues process described further on--gives an entirely satisfactory result4 ,a simple and expeditious process1 yielding intense black impressions on a white ground1 is yet to be found for the reproduction of plans1 maps1 etc41 without resorting to a negative clich or drawing4 ,,the ,,cuprotype4 7,,burnett',s ,,process47 ,this process gives positive impressions from negative clichs4 ,uranic nitrate #aj parts ,cupric nitrate #b parts ,water #ajj parts ,float for a minute strong1 well-sized paper on this solution and let it dry spontaneously in the dark4 ,expose until the image is visible1 then develop by floating on a solution of potassium ferricyanide at #e per #ajj of water--the image appears at once with a rich brown color4 ,when developed1 wash it in several changes of water until the unaltered salts are eliminated4 ,the proof is then fixed1 and1 if too intense1 can be reduced in water slightly acidified with hydrochloric acid4 ,a fine black image is obtained by toning in a solution of platinic chloride at #a per #ajj of water4 ,the chemical actions giving rise to the formation of the metallic ferrocyanide1 of which the image consists1 are quite complicated4 ,under the luminous agency the uranic nitrate is first reduced1 then the uranous oxide acts on the cupric nitrate1 forming cupric oxide1 which is finally reduced to the metallic state4 ,this metal now converts the ferricyanate in the ferro compound1 which1 by another action1 forms both cupric and uranic ferrocyanate4 ,the following uranium process gives black impressions3 ,in a saturated solution of tartaric acid dissolve freshly precipitated ferric oxide1 and keep the solution--ferric tartrate--in the dark4 ,to prepare the sensitizing solution1 dissolve #bj parts of uranic nitrate and from #a to #c parts of tartaric acid in #ajj parts of water1 and add a small quantity of ferric tartrate1 the proportion varying with the tint desired3 an excess gives a blue black4 ,with this solution brush the paper over1 and1 when dry1 expose under the negative clich1 then develop with a solution of potassium ferricyanate at #d per #ajj of water4 ,to fix1 it suffices to wash in water1 renewed three or four times4 ,as pointed out by ,mr4 ,b4 ,j4 ,burnett 7see ,introduction71 many photographic processes can be devised by basing them upon the various chemical changes1 of which uranous oxide1 reduced by light from the uranic nitrate or sulphate1 is susceptible by means of metallic or organic reagents4 ,in the ,appendix some of the most important processes1 with or without silver salts as reagents1 will be described4 ,,the ,,aniline ,,process4 ,the aniline process was published in #ahfe1 by ,mr4 ,willis1 the inventor of the platinotype47#aa7 ,it is based on the oxidation of aniline by chromic acid1 thus3 ,a sheet of paper brushed with a solution of potassium bichromate and sulphuric acid1 dried1 and after insolation under a clich exposed to the fumes of aniline which1 in reacting with the chromic compound not reduced by light1 forms a blue-black image4 ,the process gives1 consequently1 a positive impression from a positive clich4 ,there are various methods of operating2 we will briefly describe them4 ,,sensitising ,,solution4 #a4 ,potassium #f parts bichromate ,sulphuric acid #f parts ,magnesium chloride #aj parts ,water #aej parts ,willis recommended #aj parts of solid phosphoric acid instead of sulphuric acid2 the latter forms a preparation about twice more rapidly reduced4 #b4 ,potassium #aj parts bichromate ,manganous sulphate #d parts ,potassium #bj parts bisulphate ,water #cjj parts #c4 ,ammonium #e parts bichromate ,ammonium chloride #e parts ,cupric sulphate #a part ,sulphuric acid #h parts ,water #aej parts ,good well-sized paper should be employed4 ,rives is too tender and absorbs too much4 ,steinbach is better4 ,for small sizes1 whatever be the paper selected1 it is well to size it with starch and1 if possible1 to calender it on a hot steel plate1 or1 in lieu1 to iron it4 ,this is not1 however1 a sine qua non4 ,the paper is sensitized by brushing or by floating4 ,to sensitize by floating1 it should be left but for a few seconds on the solution and removed by dragging it on a glass rod in order to remove the superfluous liquid4 ,only the surface of the paper should be impregnated1 otherwise the whites would be more or less tinted and the image imbedded not as sharp4 ,sensitized1 the paper must be dried as rapidly as possible4 ,it does not keep1 and should be employed the day it is prepared or the day after1 keeping it well wrapped in paper4 ,as said above1 it is exposed under a positive clich1 plans1 designs1 etc41 drawn on tracing paper or linen4 ,the more transparent the material1 the more rapid the chemical changes4 ,during the insolation--and it is very short--the chromic compound is reduced1 the parts corresponding to the ground1 that is1 the transparent parts of the clich1 are discolored1 while those under the design remain unaltered2 the image being1 therefore1 faintly visible1 and being formed of the chromic mixture1 it is developed by the fumes of aniline in a blue black tone4 ,therefore1 if the paper be not sufficiently exposed1 the ground is colored like the image1 although not as deeply1 since the dye formed is proportionate to the more or less quantity of unreduced compound1 and if exposed too long the image is imperfectly developed or not at all by excess4 ,the discoloration of the ground1 which turns to a greenish hue1 easily indicates when the exposure is sufficient4 ,but1 to ascertain it1 the beginner should use tests as in the cyanofer process4 ,mr4 ,endemann regulates the time of exposure by partly covering a strip of the sensitive paper with a piece of the tracing material upon which the design is made1 and exposing the whole until the covered part of the paper assumes the same shade as the part directly exposed to light4 ,to develop the print is placed in the bottom of a tray1 which is then covered with a lid upon which is pinned blotting paper well imbued with an aniline and benzine mixture1 or the reverse2 that is1 exposing the print fastened to the lid and placing the aniline on the bottom of the tray4 ,the tray should be hermetically closed2 that is a condition to obtain a fine and equal coloration4 ,for this purpose the lid should be well lined with sheets of blotting paper and a weight placed over it during the operation4 ,large prints are necessarily developed in a fumigating box made ad hoc4 ,the aniline solution consists of ,aniline 7commercial for #h parts red7 ,benzine1 rectified #ajj parts ,in place of benzine1 ether ,u4,s4,p41 sp4 grav4 #j4hcg1 may be used4 ,when the proof is not over-exposed the development commences in a few minutes4 ,the image first takes a dirty black olive color which turns blue in water1 then the tone darkens to a dark-brownish tint4 ,the time of exposure to the aniline fumes depends on the time of insolation2 if short1 the ground is soon tinted1 and consequently the development should then be stopped2 if over-exposed1 the development proceeds slowly4 ,the darkest tone is obtained by a rather full exposure which admits a long fumigation4 ,sometimes the image takes a green color2 it suffices then to wash the proof in water rendered alkaline by a few drops of aqueous ammonia to obtain the normal color4 ,to somewhat improve the tone of the image and1 if objectionable1 to remove the chromic oxide which tinges the ground greenish1 the proof should be immersed in a dilute solution of sulphuric acid #a3ajj1 then washed twice1 and finally passed in ammoniacal water #a3ajj4 ,mr4 ,hermann ,endemann has published1 in #ahff1 the following process in the ,journal of the ,american ,chemical ,society1 pp4 #ahi et seq43 ,the paper1 which must be well sized with glue1 #a3ej1 is sensitized with the following solution and exposed when dry1 but still slightly damp3 ,a4 ,potassium #a ounce or #dhj bicarbonate parts ,salt #a ounce or #dhj parts ,sodium vanadate #b_/c grain or #j4ff part ,water #bj ounces or #i1fjj parts ,b4 ,sulphuric acid #b ounces or #ifj parts ,water #aj ounces or #d1hjj parts ,when cold mix to ,a4 8,from the composition of the solution10 says ,mr4 ,endemann1 8it is evident that it must be strongly acid2 but when this solution is exposed to light1 in the presence of the organic substances of the paper1 the acidity of the solution disappears1 we obtain potassium and sodium sulphates1 basic chromium sulphate1 salt and vanadic acid4 ,while1 therefore1 the unchanged parts of the paper remain acid1 the changed parts acquire a neutral reaction1 and while the first will readily assimilate bases1 the second will not4 ,exposed in an atmosphere laden with water and aniline1 the aniline will be absorbed in those parts where the solution remains acid and in proportion to the remaining acidity40 ,to develop the image the paper is spread over the opening of a frame tightly placed on a pan1 in the bottom of which is heated a solution of aniline in water1 #a3ej1 until the image appears brown1 and for further development in a box laden with steam water1 which1 according to ,mr4 ,endemann1 requires two hours to obtain a deep black coloration4 ,to remove the chromium compound the picture is immersed in a solution of aqueous ammonia1 #a3f1 then washed and dried4 ,a few years ago the aniline process was improved by developing the image with the aniline-benzine mixture vaporized by steam in a box made specially for that purpose1 whereby a reproduction can be obtained in less than ten minutes4 ,in the photographic department of ,messrs ,poulson ,eger's ,hecia ,architectural and ,ornamental ,iron ,works1 which is directed by ,charles ,bilordeaux1 this process is worked in the following manner3 ,the developing is made of sheet iron with a door sliding up and down1 it being balanced by a counterpoise1 and provided with a chimney4 ,in the box is a gutter1 extending the whole length of the bottom1 covered with muslin and connected to a steam pipe2 there is also a coil similarly connected4 ,after the insolation1 which requires about one minute in sunshine1 the print is suspended in the box1 the muslin brushed over with the solution of aniline1 and live steam allowed to pass through the gutter for only two minutes1 whereby the aniline being vaporized acts on the chromic salt and develops the image2 then the steam is allowed in the coil1 and1 in from three to four minutes1 the paper is dry and the picture finished4 ,the image stands on a slightly greenish ground1 which is not objectionable for the purpose the reproductions are made4 ,the sensitizing solution is similar to that published by ,mr4 ,endemann1 viz43 ,potassium bichromate #dfj grams ,sodium chloride #dfj grams ,ammonium vanadate #j4ge gram ,sulphuric acid #a liter ,water #ac liters ,,the ,,primuline ,,or ,,diazotype ,,process4 ,primuline1 discovered in #ahhg by ,mr4 ,a4 ,g4 ,green1 an ,english chemist1 is a dye of a primrose color1 possessing a great affinity for cotton fibers1 to which it is readily fixed by simply immersing the material for a few moments in a hot solution of the dye4 ,if the material so dyed be placed in an acidified solution of nitrous oxide1 the primuline is diazotized1 forming a derivative compound of a deeper color1 which fades in the light1 and which in presence of amines and phenols gives rise to a variety of dyes whose color depends on the reagent employed1 while1 when acted on by light1 the resulting compound is entirely deprived of this property4 ,in other words1 the diazotized primuline acts as a mordant only when not altered by the luminous action4 ,the chemical change light effects in the diazotized primuline is not well known4 ,it is pretty certain1 however1 that nitrogen is set free1 for if gelatine imbued with primuline be immersed in water after insulation1 nitrogen is set free and can be collected as usual in a tub filled with water and inverted on the substance4 ,by itself diazotized primuline is slowly influenced by light1 but quickly acted on in presence of organic substances4 ,it is more sensitive when applied on cotton or paper than on wool1 silk1 linen1 and such organic compounds as gelatine1 albumen1 caseine1 starch1 etc4 ,its sensitiveness is about one-tenth less with gelatine than with cotton4 ,the sensitiveness of diazotized primuline to light1 when united to organic substances and the different colors which can be obtained with the unaltered compound1 have given rise to an interesting printing method1 the invention of ,messrs4 ,a4 ,g4 ,green1 ,c4 ,f4 ,cross1 and ,e4 ,j4 ,bevan1 which yields positive impressions from positive clichs4 ,the manipulations of the process are simple3 ,in a certain quantity of rain water1 kept at nearly the boiling temperature by an alcohol lamp placed under the vessel1 dissolve per cent4 #b parts of commercial primuline1 and in this immerse1 by means of a glass rod1 some pieces of calico--free from dressing--turning them over several times during the immersion4 ,when the fibers are well imbued1 which requires from four to five minutes1 remove the calico with the glass rod and rinse it thoroughly in water4 ,this done1 wring out the superfluous liquid as much as possible1 and1 finally1 immerse each piece separately in a solution of ,sodium nitrite1 #g parts commercial ,hydrochloric acid1 #af parts commercial ,water #ajj parts ,after turning the pieces of calico two or three times over1 they are rinsed to eliminate the acid1 then drained and placed between sheets of blotting paper to dry4 ,all this1 except the impregnation with primuline1 should be done in the dark room4 ,as said above1 primuline is transformed by nitrous oxide into a diazotized compound1 and consequently the material is now susceptible of being acted on by light4 ,it does not keep1 and should be exposed1 etc41 soon after its preparation4 ,paper is impregnated with primuline either by floating or brushing4 ,the best results are obtained with paper previously sized with arrowroot or gelatine in order to keep the image entirely on the surface of the paper4 ,linen1 silk and wool are treated as calico4 ,the clichs should be positive to obtain positive expressions and somewhat more opaque than those employed in the processes before described1 else vigor and intensity could not be obtained4 ,here we must state that the primuline process seems to be better adapted for the reproductions of drawings1 such as made for the black process1 and of opaque photo-clichs in lines1 or white and black1 than for printing in half tone4 ,when the material to print upon is thick and wholly impregnated with diazotized primuline1 it is advisable1 since the insulation could not be prolonged to effect the change through1 to expose the back of the material for a certain but short period in order to clear it4 ,this is especially advantageous when the clich is not of good intensity4 ,during the exposure1 which varies from #cj seconds to #aj minutes and more by a dull light1 the progresses of the luminous action is seen by the bleaching of the material which assumes a dingy coloration4 ,but in order to ascertain when the decomposition is complete on the ground of the image1 it is well to use tests as in the cyanofer process1 dipping one of them in the developer from time to time4 ,the developers are compounded as follows3 ,,for ,,red4 ,beta-naphthol #d parts ,caustic potassa #f parts ,water #ejj parts ,rub the alkali and the naphthol with a little water in a mortar and add the remainder of the water4 ,,for ,,orange4 ,resorcin #c parts ,water #ejj parts ,when dissolved add ,caustic potassa #e parts ,,for ,,yellow4 ,carbolic acid1 cryst #e parts ,water #ejj parts ,,for ,,purple4 ,naphthylamine #f parts ,hydrochloric acid1 in #f parts volume ,mix in a mortar1 then add ,water #ejj parts ,,for ,,black4 ,eikonogen1 white crystals #f parts ,water #ejj parts ,pulverize the eikonogen1 add the water and1 at the same time1 the material on its removal from the printing frame1 and keep in motion until the development is effected4 ,,for ,,brown4 ,pyrogallol #e parts ,water #ejj parts ,after the development1 which requires but a few moments1 it suffices to wash the material to fix the image by eliminating the soluble compounds4 ,however1 for purple the material should be passed in a dilute solution of tartaric acid and not washed afterwards2 it should remain acid4 ,when it is desirable to obtain an impression in several colors1 the various developers are thickened with starch1 then locally applied with a brush on the image1 which is always visible after exposure4 ,for printing on wood1 glass and porcelain1 see further on4 ,,printing ,,on ,,wood1 ,,canvas1 ,,opal1 ,,and ,,transparencies ,printing on ,wood4--,to print on a wood block a design to be engraved on the same presents certain difficulties4 ,in the first place1 the sensitizing solution must not be absorbed by the wood1 but remain wholly on its surface2 then the photo film1 although thick enough to produce an image sufficiently intense to be distinctly visible in all its details1 should not scale or clip away under the graver1 and not interfere in any way with the work of the artist2 the least touch of the graver must reach the wood and make its impression4 ,lastly1 the design should be permanent4 ,these difficulties will be avoided by adhering to the instructions given in the lines following4 ,the solution to render impervious the surface of the wood consists of ,common gelatine #e parts ,gum arabic #c parts ,castile soap #c parts ,water #ajj parts ,dissolve by heat on a water bath4 ,to apply it1 the wood is rubbed with fine sandpaper1 then heated over a spirit lamp to about #hf deg4 ,fahr4 7#cj deg4 ,c47 and upon it is poured in excess the liquefied and quite warm solution1 which must be allowed to penetrate in the pores of the wood by letting it gelatinize1 when it is wiped off clean4 ,nothing must remain on the surface of the wood4 ,this done1 and while still damp1 the preparation is rendered insoluble by pouring over a solution of alum at #e per #ajj of water4 ,the object of this preliminary operation is to render the wood impervious1 and therefore to prevent the sensitizing solution to penetrate its texture4 ,the wood is then heated again and its surface whitened with a little silver white or sulphate of barium1 diffused in a small quantity of the following warm solution3 ,gelatine #a parts ,alum #j4a part ,water #ajj parts ,while wet1 this is smoothed with a jeweler's brush1 taking care to leave on the wood1 a very thin layer of the mixture1 only sufficient to obtain a white surface which1 by contrasting with color of the wood assists the engraver in his work4 ,the wood should now be allowed to dry thoroughly1 when it is coated with a tepid solution of ,isinglass #c parts ,water #ajj parts and dried4 ,now the sensitizing process differs according as whether the clich is positive or negative4 ,in the former case the preparation is sensitized with the solution employed in the black process1 proceeding afterwards as usual2 in the latter1 that is1 when the clich is negative1 the best process is the cuprotype47#ab7 ,for printing1 special frames are employed to permit one to examine the progress of the impression from time to time without the possibility of either the wood block or the clich moving4 ,these frames open in two4 ,the upper frame is provided with screws on the four sides to hold firmly the block when it is placed into contact with the clich by means of the screws fixed on the cross bars4 ,as to the clich1 if it is made on a glass plate1 it is secured on the thick glass plate of the lower frame by two wooden bars against it pushed by screws4 ,when the block is ready for printing1 the prepared side is usually concave4 ,it is straightened by slightly wetting the back and resting it on one end1 prepared side against the wall4 ,printing on ,canvas4--,the canvas should be first brushed with a solution of aqueous ammonia in alcohol1 #a3c1 to remove greasiness until the thread just commences to show1 then1 when rinsed and dry1 rubbed with fine sand to give a tooth1 dusted1 washed with a sponge and then coated with the following solution1 proceeding afterwards as in the cuprotype process3 ,isinglass #h parts ,uranic nitrate #e parts ,copper nitrate #b parts ,water #bjj parts ,printing on ,opal1 ,celluloid1 etc41 is quite simple2 it suffices to coat the material with the following gelatine solution1 and1 when the film is dry1 to proceed in operating by any one of the processes before described4 ,the sensitizing compound may be incorporated to the gelatine solution1 but we prefer not to do it and to sensitize the plates as they are wanted for use4 ,a4 ,gelatine #d parts ,water #gj parts in volume ,dissolve and mix little by little in order3 ,b4 ,chrome alum #j4be parts ,water1 hot #bj parts ,c4 ,alcohol #aj parts ,when coated place the plates on a level stand until the gelatine is set1 and let them dry on a rack4 ,transparencies4--,prepare the plate as directed above with ,a4 ,gelatine #f parts ,water #gj parts ,b4 ,chrome alum #j4c part ,water1 hot #bj parts ,c4 ,alcohol #aj parts ,sensitize with the uranic-copper solution employed in the cuprotype4 ,by this process transparencies of a rich brown1 not actinic1 color are obtained4 ,consequently they can be used to reproduce negatives by the same process4 ,for lantern slides they may be toned black by platinic chloride4 ,to strip off the picture1 apply1 first1 on the glass plate a substratum of ,india rubber1 #b to #ajj of benzole1 coat with plain collodion1 immerse the plate in water as soon as the film is set1 and when greasiness has disappeared pour on the gelatine solution and proceed4 ,for tranferring on any material1 a sheet of paper is immersed in a solution of ,india rubber cement in #bj parts of benzole1 dried1 coated with the gelatine solution1 sensitized1 etc41 by operating in the ordinary manner4 ,after development1 the proof1 being dry1 is brushed over with alumed gelatine moderately warm1 dried1 immersed in tepid water until the gelatine is softened and tacky1 when it is placed on the material and squeezed into contact4 ,this done1 the transfer should be allowed to dry thoroughly4 ,now1 by imbuing the proof with benzole to dissolve the ,india rubber1 the paper is easily stripped off1 leaving behind the picture adhering to the material4 ,,tracing ,,process ,,on ,,metal4 ,we call the attention of metal engravers to this process4 ,it is well known that wood engravers have their original designs photographed on the block in order to save considerable time by not making the drawing themselves2 moreover the cost is nominal1 so to say1 and the copy more true and perfect than it can be done by hand4 ,why should not the copper engraver and the aquafortist avail themselves of the same advantages8 ,a few do it secretly1 no doubt1 but the generality not knowing the process1 or1 if so1 not having tried it1 think it is not possible or that it may spoil their plates4 ,this is an error4 ,it can be done and very easily by adhering to the following instructions3 ,dissolve #b parts of ammonium bichromate in #ajj parts of water1 and in this let soak for an hour or so #aj parts of ,coignet's best gelatine1 then dissolve on a water bath1 filter through flannel1 and the solution is ready for use4 ,before being coated1 the plate should necessarily be cleaned free from oxidation and greasy matters4 ,this is done by immersing the plate for a few moments in a warm solution of common potash1 then rinsing and rubbing it with chalk moistened with a little water1 when after rinsing again and draining the plate should be immediately prepared4 ,to spread the gelatine solution in an even and thin layer1 a tournette is employed4 ,the most simple consists of a round wooden stick of which the upper part is carved in the form of a cup with an edge1 or rim1 about one quarter of an inch broad4 ,on this rim is melted some gutta-percha1 upon which the plate is pressed into contact and adhers quite firmly when the gutta-percha is solidified4 ,the stick is perforated at the lower end and revolves on an iron pivot fixed at the bottom of the support1 being held in the opening on the platform of the same1 as shown in the diagram on the following page4 ,the plate being fastened to the tournette1 the warm gelatine solution is flowed over it and spread to the edges by means of a glass rod or a piece of cardboard1 avoiding air bubbles4 ,this done the tournette is set into motion1 and when the film is equalized1 which is done in a moment1 the plate is detached1 placed on a leveled stand and slowly dried with the spirit lamp4 ,a ,tournette ,by a good light the exposure on the shade does not exceed twenty minutes with a pretty intense transparency1 and should be regulated with a photometer4 ,when the insulation is sufficient1 the image is slightly visible1 and should be so4 ,the plate is then bordered with banking wax and bitten-in with a solution of ferric chloride at #de deg4 ,baum1 or-- ,ferric chloride1 crystal #bj parts ,hydrochloric acid #a part ,water #ajj parts ,the parts of the gelatine film the most acted on are impermeable1 so to say1 and consequently do not allow the etching fluid to penetrate to the copper2 while those the least impressed are permeated according as to their degree of insolation1 ,therefore1 when the ferric chloride solution is poured upon the film and carefelly brushed over with a soft brush1 in a few moments the image progressively appears1 the deep blacks first1 then the half tints1 and lastly the most delicate details1 the whole requiring but a few minutes4 ,it is now that the etching action should be stopped by washing under the tap4 ,however1 should by excess of exposure1 or any other cause1 the details not appear within five or six minutes1 the ferric chloride should nevertheless be washed off1 for then it may find its way under the film and the plate would be spoiled4 ,after washing the gelatine is dissolved in a solution of potash1 etc41 when the image would be found slightly engraved4 ,should the image be in half-tints1 it would be advisable to apply a grain of rosin on the gelatine film just before etching4 ,to engrave on steel the operations are the same1 but on its removal from the printing frame the plate should be soaked with water renewed several times until the bichromate is washed off4 ,the film is then dried spontaneously and afterwards flowed for about two minutes with the ,solution ,a1 then1 this being thrown away1 with the ,solution ,b1 which is allowed to act for a similar period4 ,a4 ,nitric acid1 pure #abj parts ,silver nitrate #f parts ,alcohol1 #ie deg #ej parts ,water #ge parts ,b4 ,nitric acid1 pure #e parts ,alcohol1 #ie deg #dj parts ,water #fj parts ,,graphotypy4 ,this process consists in converting a clich in half tones into one in lines1 which can be directly printed on paper1 or impressed1 by means of an ink transfer made as explained before1 on a stone1 or on a zinc or copper plate for etching in relief1 or in intaglio1 according as the clich is negative or positive4 ,a clich on gelatine1 but preferably on a collodion film1 is varnished with a solution of yellow wax and bitumen in benzole and turpentine-oil3 ,bitumen of ,judaea #h parts ,yellow wax #b parts ,benzole #dj parts ,turpentine oil #fj parts 7filter7 then etched as done to engrave in the aquafortis manner1 the corrections being made by applying with a brush some of the above varnish on the defective parts1 which are worked over when the varnish is dry4 ,the tools are simply needles of various thickness ground in sharp square and round points of different sizes4 ,when the etching is finished1 the parts which should form the ground1 or white parts of the design1 being covered with the bitumen varnish is non-actinic1 or1 in other words1 does not admit the light acting on the sensitive plate preparation employed to reproduce the design1 except by an exposure a good deal longer than that necessary to reduce the metallic salts4 ,the engraver will see at once that1 although it greatly simplifies the copying work and1 consequently1 saves much time1 this process does not1 however1 bind him to any rules and leaves him perfectly free to follow its inspirations and make such alterations as he thinks proper to produce artistic effects2 in a word1 the reproduction will no more be a picture taken by a mechanical process1 so to say1 but an original drawing reflecting his talent and characteristic manner4 ,a similar process much employed by photo engravers1 and presenting the same advantages1 is to convert an ordinary photograph on paper--or a blue print1 as devised by the writer--into a design in lines by drawing with ,india ink1 or the special ink of ,higgins1 and1 this done1 to wash off the photographic image1 the design being afterwards reproduced by the ordinary processes as a negative or a positive clich4 ,when the photograph is a silver print especially made for the purpose in question and1 consequently not toned1 but simply fixed in a new thiosulphate 7hyposulphite7 bath1 and well washed--it is bleached by flowing over a solution of-- ,bichloride of mercury #e parts ,alcohol #dj parts7#ac7 ,water #ajj parts ,if the photograph has been toned1 i4e41 colored by a deposit of gold1 or if it was fixed in a thiosulphate bath in which toned prints have been fixed1 then the image is dissolved by treatment in a solution of potassium cyanide in alcoholized water4 ,when a blue photograph is reduced1 it is advisable before drawing upon it to first reduce its intensity by a prolonged immersion into water4 ,pale blue is a very actinic color which is not reproduced in photography1 except by the ortho-chromatic process1 or if it does1 the impression being very weak1 is not objectionable4 ,when the image has not been sufficiently or not at all bleached1 the blue is dissolved by an alcoholized solution of the blue solving4 ,,the ,,uranotype4 ,this process1 devised by ,j4 ,wothly1 in #ahfd1 did not receive from the photographers the attention it merits1 as it is always the case when a process is patented1 and can be replaced by another equally practical which is not4 ,it gives pictures of a very good tone1 which are quite permanent2 we have some made in #ahff1 which are suffered no change whatever1 they seem to have been printed from yesterday4 ,the first process given by ,wothly does not appear to be complete4 ,it has been well described by ,h4 ,cooper and a gentleman who signs by the initial letter ,x4 ,the process published in #ahfe by ,wothly is as follows3 ,a sheet of paper is sized by brushing with a paste made of #bd parts of arrowroot in #ejj parts of water1 to which are added a few drops of a solution of citric or tartaric acid1 then coated with a collodion consisting of #ajj cubic centimeters of plain collodion1 a few drops of oil of turpentine and #cj cubic centimeters of the following sensitizing solution3 ,nitrate of uranium #cj to #ij parts ,chloride of platinum #b parts ,alcohol #ahj parts ,the time of exposure is about that required for paper prepared with silver chloride4 ,the image is bluish-black but weak4 ,after washing the print is immersed in a solution containing #j4e parts of chloride of gold for #b1jjj parts of distilled water1 and then fixed in a bath of sulphocyanate of potassium1 which tones the image blue-black4 ,it may happen that the proof is slightly tinted red4 ,this arises from a small quantity of lime in the paper which forms uranate of calcium4 ,to prevent the proofs turning yellow1 it should be washed in an exceedingly weak solution of acetic acid4 ,if1 after exposure1 the print is immersed1 without it being washed1 in the gold bath1 the image becomes rose-red1 but the whites remain pure4 ,the effect is peculiar4 ,h4 ,,cooper',s ,,process 7#ahfe74 ,,preparation ,,of ,,the ,,paper ,st4 ,vincent arrowroot #bjj grains ,boiling water #aj ounces ,crush the arrowroot to fine powder1 then rub it to a paste with a little water1 and let an assistant pour a few drams of boiling water while you keep stirring all the time2 finally1 let him add the rest of the boiling water1 the operator still continuing the stirring4 ,the paste is allowed to cool1 and will be thicker when cold than when hot4 ,remove the upper portion entirely when quite cold1 otherwise1 if any left1 it will give rise to streaks4 ,the author insists upon the necessity of all these cares4 ,two sheets of paper are now placed side by side on a flat board1 then the surface of the first is covered with the paste by means of a sponge1 proceeding1 before you leave it1 all over the sheet in a horizontal direction2 the second sheet is covered in a like manner4 ,by the time the second sheet is pasted1 the first one will be partially dry4 ,the sponge is now drawn over each sheet1 in succession1 in a perpendicular direction in order to efface the streaks from the first sponging4 ,if the paste drags in a slimy manner1 it is too strong1 and a fresh arrowroot must be prepared1 because dilution only ends in failure4 ,why dry1 the paper is rolled under moderate pressure1 and when it lies smoothly the maximum pressure may be applied4 ,,plain ,,collodion4 ,alcohol #ab ounces ,ether #d ounces ,pyroxyline #hj grains ,,sensitive ,,collodion4 ,plain collodion #a ounce ,nitrate of uranium1 pure #cj grains ,nitrate or silver #e grains ,add the uranium first1 and as soon as it has dissolved all that it can1 add a grain or two of soda1 and when settled pour off the supernatant collodion and add the silver47#ad7 ,to coat the paper with collodion1 use a board with a handle beneath1 such as is used by plasterers4 ,on this place a sheet of paper1 the edges being turned up about the sixteenth of an inch2 this enables the whole of the sheet to be covered without spilling the collodion or allowing it to run on the back of the paper4 ,there is a marked difference in the appearance of the prints when they leave the pressure frame4 ,some samples of collodion cause the picture to print of a beautiful green1 others of a rich brown1 and some of a yellow or orange tint4 ,the last take the longest of all to tone1 and difficultly assume the tint of well toned silver prints17#ae7 those printing to green or brown tone very rapidly4 ,after printing the pictures are placed in diluted sulphuric acid1 #a to #cj of water1 until the high lights are perfectly clear and white2 this takes from ten to fifteen minutes4 ,after washing well under a stream of water1 they are placed in the toning and fixing bath4 ,,toning ,,and ,,fixing ,,bath4 ,sulphocyanide of ammonium #a ounce ,water #ab ounces ,chloride of gold #a to #c grains ,after removing from this bath1 the prints are immersed for a few moments in water1 and then rapidly washed4 ,,formula ,,for ,,preparing ,,the ,,pyroxyline ,nitric acid1 sp4 gr4 #a4cj #ab fluid ounces ,sulphuric acid1 sp4 gr4 #cf fluid ounces #a4hde ,water #h fluid ounces ,temperature #acj degrees ,fahr4 ,time of immersion #ae minutes4 ,x',s ,,process 7#ahfe74 7,secrets of the ,uranotype7 ,preparation of the ,uranium ,compound4--,precipitate the nitrate of uranium from its solution by concentrated liquid ammonia4 ,let settle the precipitate1 decant1 and wash in several changes of water4 ,dissolve it by heat in pure nitric acid1 taking care not to add an excess of acid4 ,the ammonio-nitrate of uranium salt is then crystallized and dried4 ,mix a solution of #f drams of this salt1 dissolved in #c drams of water1 to a solution of #ae grains of silver in #cj minims of water1 and crystallize4 ,this salt is called ammonio-nitrate of uranium and silver4 ,,sensitizing ,,solution4 ,ammonio nitrate salt #c drams ,alcohol #h drams ,distilled water #ae drops ,nitric acid1 pure #a drop ,plain ,collodion4--,dissolve in a small quantity of ether #a dram of ,canada balsam and #a dram of castor oil1 filter and let evaporate the solution to the consistency of oil4 ,of this1 add #aj minims to a collodion made of ,alcohol #aj ounces ,ether #bj ounces ,pyroxyline #bbj grains ,,sensitive ,,collodion ,plain collodion #ab drams ,sensitizing solution #f drams ,nitric acid #b or more drops ,keep this collodion in the dark1 as it is quite sensitive4 ,,preparation ,,of ,,the ,,paper ,arrowroot1 pulverized #a ounce ,water #cb ounces ,solution of acetate of #aj drops lead ,heat to #ajj deg4 ,fahr4 and then add four ounces of albumen4 ,the paper is floated on this solution for five minutes and hung up to dry4 ,the sizing may also be applied with a sponge in the manner often described4 ,the proofs should be slightly over-printed and1 before toning and fixing1 placed for about ten minutes in the following solution3 ,distilled water #dj ounces ,acetic acid #a ounce ,hydrochloric acid #a ounce ,after washing in several changes of water1 the proofs may be toned in any toning bath1 and then fixed with sulphocyanide of potassium1 washing afterwards in the usual manner4 ,,the ,,platinotype4 ,this process1 discovered by ,william ,willis17#af7 yields very fine impressions which wholly consists of platinum and are1 therefore1 chemically permanent4 ,it has been described theoretically and practically by ,pizzighelli and ,kbl in a paper for which the ,vienna ,photographic ,society has awarded the ,voightlander prize47#ag7 ,the following is an abridgment of this important process1 as described by the authors3 ,the paper1 calendered or not17#ah7 is sized with gelatine or arrowroot4 ,the color of the proof with the latter size is brownish black1 and bluish black with the former4 ,to prepare the gelatine solution #aj parts of gelatine are soaked in #hjj parts of water and then dissolved at a temperature of #fj deg4 ,c4 7#adj deg4 ,fahr471 when #bjj parts of alcohol and #c parts of alum are added and the solution filtered4 ,to prepare the arrowroot solution #aj parts of the substance are powdered in a mortar with a little water and mixed to #hjj parts of boiling water1 added gradually in stirring4 ,after boiling for a few minutes #bjj parts of alcohol are added and the mixture filtered4 ,these solutions are employed warm4 ,the paper is immersed for two or three minutes and hung up to dry in a heated room1 then immersed a second time and dried by hanging it up in the opposite direction1 in order to obtain an even coating4 ,the potassic platinic chloride is an article of commerce4 ,it should be soluble without residue in #f parts of water and without acid reaction4 ,in this proportion it constitutes the normal stock solution employed in the various formulas4 ,the standard ferric oxalate solution is also found in commerce4 ,treated by potassium ferricyanate it should not be colored blue1 nor become turpid when diluted with one-tenth part of water and boiled4 ,the former reaction indicates that it contains no ferrous salt1 and the latter no basic oxalate4 ,the authors give the following instructions for preparing the ferric oxalate solution1 to which they attach much importance3 ,five hundred parts of ferric chloride are dissolved in #e1jjj parts of water and heated to boiling1 when a solution of soda is added until the liquid becomes alkaline47#ai7 ,about #bej parts of caustic soda are generally employed for this purpose4 ,the precipitate--ferric oxide--is now washed in warm water until the last washing water is quite neutral to test paper1 then drained and mixed with #bjj parts of pure crystallized oxalic acid4 ,the mixture is then allowed to stand in the dark for several days at a temperature not exceeding #cj deg4 ,c4 7#hf deg4 ,fahr47 ,at first the solution from green turns to a yellow green1 and finally becomes almost brown4 ,at this moment the excess of ferric oxide is filtered out and the liquor submitted to a quantitative analysis1 the result of which leads to ascertain the quantity of ferric oxalate in #ajj parts of the solution and the excess of oxalic acid4 ,the solution should then be diluted with distilled water1 such as it contains #bj parts of ferric oxalate per #ajj parts of water1 and oxalic acid must be added in the proportion of from #f to #h per #ajj of the ferric oxalate1 taking into account the quantity of acid the solution already contains4 ,the solution should be kept in the dark4 ,it is altered by light47#bj7 ,,iron ,,chlorate ,,solution ,ferric oxalate solution #ajj parts ,potassium chlorate #j4d parts ,this solution is employed to obtain more contrasts4 ,,preparation ,,of ,,the ,,sensitizing ,,solution ,platinum solution #ab parts ,ferric oxalate solution #aa parts ,distilled water #b parts ,this solution gives very soft tones with intense black4 ,to obtain more brilliancy we use the following proportions3 ,platinum solution #ab parts ,ferric oxalate solution #i parts ,chlorate of iron solution #c parts ,distilled water #b parts ,to obtain results comparable to those which the silver printing out process gives1 the following mixture is employed3 ,platinum solution #ab parts ,ferric oxalate solution #h parts ,chlorate of iron solution #d parts ,distilled water #h parts ,for very weak negatives1 reproductions of drawings1 etc41 we use-- ,platinum solution #ab parts ,chlorate of iron #aa parts ,distilled water #b parts7#ba7 ,to obtain proofs not completely black1 as1 for example1 reproductions of lead drawings1 the solution may be diluted with half or the whole volume of distilled water4 ,but if the solution be applied on little absorbent surfaces or on paper strongly sized it is not advisable to dilute it4 ,preparation1 of the ,paper4--,the paper should be kept slightly moist in order that it does not too completely absorb the sensitizing solution4 ,therefore1 when the atmosphere is very dry1 it is well to keep the paper in a damp place1 in the cellar for example4 ,before sensitizing1 which should be done by a very diffused light1 a quantity of the solution proportionate to the surface to be sensitized 7about #ae c4c41 for a whole sheet of ,rives' or ,saxe paper7 must be measured1 and spread with a large brush7#bb7 on the paper fixed with drawing pins on a board covered with a sheet of blotting paper4 ,when well impregnated1 the paper is hung up to dry in the dark room1 and as soon as the apparent dampness of the surface has disappeared1 it should be dried immediately at a temperature of #cj--dj deg4 ,c4 7#hf--aja deg4 ,fahr74 ,if the paper be dried too rapidly the sensitive compound remains on its surface1 and in developing the image does not come out well4 ,if1 on the other hand1 the drying is too slow1 the solution penetrates too much in the paper and the image is wanting of vigor and does not appear very sharp4 ,one cannot depart from this rule that the desiccation from the moment the solution has been applied until the paper is dry should last no more than from twelve to fifteen minutes4 ,the sensitized paper is hygroscopic and must be preserved in a calcium box4 ,it is a conditio sine qua non that the paper must be quite dry before1 during1 and after printing1 to obtain good results4 ,dampness is the greatest enemy in this process4 ,for printing a pad of ,india rubber should be placed over the platinum paper to prevent it from attracting the atmospheric moisture1 and in damp weather it is even advisable to cover it with several sheets of blotting paper previously heated before the fire4 ,the platinum paper is at least three times more sensitive than the silver paper used in the printing-out process1 under the reductive action of light the yellow color of the prepared paper turns brown and then becomes of a lighter color1 nearly orange1 so that the darker parts of the image often appears more luminous than the dark half tints4 ,no rule can be given to regulate the insolation1 but after a few trials it is easy to judge when it is right by observing the progress of the reduction and the color of the image4 ,the orange color indicates the complete reduction of the ferric oxalate4 ,when the details in the lights are faintly visible1 the exposure is generally right4 ,the developer consists of an almost saturated solution of potassium oxalate acidified by oxalic acid1 and for use heated to #hj--he deg4 #j4 7#agf--ahd deg4 ,fahr4717#bc7 in an agate glazed iron tray placed upon a water bath at the above temperature4 ,by simply drawing the proof over it1 the image is at once developed47#bd7 ,when the proof is thought to be over-exposed1 the oxalate solution can be employed at a lower temperature4 ,if1 on the contrary1 it is under-exposed1 the solution may be heated even to the boiling point4 ,the developer can be used over and over again4 ,it should always have an acid reaction4 ,according to ,mr4 ,borlinetto a sepia tone is obtained by using the following cold developer3 ,saturated solution of #abj parts potassium oxalate ,saturated solution of #ac parts copper chloride ,oxalic acid #a4e part ,after developing the proofs are immediately immersed for fixing in a solution of hydrochloric acid1 #a to #hj of water1 renewed so long as the paper is tinged yellow 7about three times71 leaving the proofs ten minutes in each solution4 ,lastly1 they are washed to remove the acid4 ,the platinotype has been still improved by ,captain ,pizzighelli1 who devised the following methods of operating by which the impressions are obtained by the continuous action of light1 that is1 without development1 thus rendering the platinotype just as simple as the ordinary printing-out silver process4 ,in these new processes to the sensitizing solution is added the alkaline oxalate1 which effects the reduction of the platinous salt during the exposure to light4 ,consequently the prepared paper is insolated until the image appears as it should be1 or--which is exceedingly useful in cloudy weather--until it is entirely visible but still deficient in delicate half tones1 for in the dark the action proceeds and the image developing itself will be found finished in a period which may extend to a few hours4 ,but it can be1 however1 developed in a few seconds by immersion in a cold or slightly warm solution of sodium carbonate1 #a3be of water4 ,the image is fixed as directed in the foregoing process4 ,the paper1 prepared exactly as in the former process and kept in the calcium box until wanted for use1 should not be employed quite dry1 but allowed to absorb a little moisture by hanging it in the dark room4 ,hence1 the ,india rubber and other protecting pads can be dispensed with4 ,they are even objectionable1 for dampness is absolutely necessary to promote the chemical changes by which the image is developed4 ,a4 ,,ammonio-,,ferric ,,oxalate ,,solution ,ferric oxalate solution #ajj parts ,neutral ammonium oxalate #ah to #bj parts ,b4 ,,sodio-,,ferric ,,oxalate ,,solution ,ferric oxalate solution #ajj parts ,neutral sodium oxalate #ae to #ah parts ,to prepare these two solutions the ammonium or sodium oxalate is dissolved by small quantities at a time1 and when the emerald color due to the formation of the double oxalate commences to darken1 the saturation being then complete1 no more of either salt should be added4 ,the solution is now well shaken with #c parts of glycerine1 allowed to settle and filtered4 ,any one of the double oxalates can be used4 ,the ammonium tends to produce softer pictures and bluish tones4 ,to obtain more contrasts a little potassium chlorate may be added4 ,c4 ,,iron ,,chlorate ,,solution ,solution ,b #ajj parts ,potassium chlorate #j4d part ,d4 ,,mercuric ,,solution4 ,mercuric chloride #bj parts solution at #e3ajj ,sodium oxalate solution #dj parts at #c3ajj ,glycerine #b parts ,,sensitizing ,,solutions4 ,,for ,,black ,,tones4 ,platinite solution1 #a3f #e parts ,solution ,b #f parts ,solution ,c #b parts ,,for ,,sepia ,,tones4 ,platinite solution1 #a3f #e parts ,solution ,c #d parts ,solution ,d #d parts ,intermediate tones are obtained by diminishing the dose of ,c and replacing it by an equal volume of ,b4 ,for this process the paper should be sized with ,arrowroot #b parts ,sodium oxalate at #c3ajj #ajj parts ,to dispense with this preliminary sizing ,captain ,pizzighelli adds gum arabic to the platinite solution1 whereby the sizing and sensitizing are done in one operation4 ,the gum arabic solutions are prepared as follows3 ,e4 ,gum arabic in #dj parts powder ,sodium ferric #dj parts oxalate solution1 ,b ,sodium oxalate #ajj parts solution at #c3ajj ,glycerine #c parts ,place the glycerine and the gum arabic in a mortar1 then1 stirring with the pestle1 dissolve by adding1 little by little1 the mixture1 heated to #dj--de deg4 ,c4 7#ajd--aac deg4 ,fahr471 of the solution of sodium ferric oxalate and sodium oxalate4 ,let stand for about two hours and grind again to dissolve entirely the gum arabic4 ,filter through muslin4 ,f4 ,mercuric chloride #bj parts solution1 #e3ajj ,sodium oxalate solution1 #dj parts #c3ajj ,gum arabic in powder #bd parts ,glycerine #b parts ,dissolve as said above4 ,,sensitizing ,,solutions4 ,,for ,,black ,,tones4 ,platinite solution1 #a3f #e parts ,solution ,e #f parts ,solution ,c #b parts ,,for ,,sepia ,,tones4 ,platinite solution1 #a3f #e parts ,solution ,c #d parts ,solution ,f #d parts ,mix just before use4 ,the solutions do not keep4 ,the paper prepared by either one of these two processes can be exposed as in the old process1 and the image developed bythe hot oxalate solution4 ,the preparation of wood1 canvas1 etc41 for the platinotype printing need not to be described2 it suggests itself4 ,,causes ,,of ,,failures4 ,the images are veiled4 ,this defect may result from various causes1 viz43 #ast4 ,the stock ferric oxalate solution is impaired by a partial reduction of the ferric salt into ferrous oxalate4 ,the solution should be preserved in an orange colored vial1 and kept in the closet of the dark room4 ,it should be tested from time to time for the ferrous salt with a solution of potassium ferricyanate4 ,if it does not contain any ferrous oxalate it can be used by adding to it a little of the iron chlorate solution4 #b;d4 ,the paper has been exposed to light during the sensitizing or the subsequent operations4 ,one should bear in mind that the platinum paper is twice more sensitive than silvered paper4 #c;d4 ,the sensitized paper has been dried at a temperature above #dj deg4 ,c4 7#ajd4 deg4 ,fahr47 #dth4 ,over-exposure4 ,the proofs are not sharp4 #ast4 ,the sensitive paper has absorbed moisture4 #b;d4 ,it is too old4 ,the paper cannot be kept good for over six weeks1 unless special care be taken4 ,according to ,mr4 ,bory1 the sensitive paper altered by keeping is restored to its original good quality by simply brushing it over with a solution of #j4je parts of potassium chloride or the same quantity of potassium chlorate in #ajj parts of distilled water1 or a mixture of these two solutions1 or one of iron chlorate4 ,by treating the insolated paper with these solutions1 the image is destroyed1 and the paper can be used again4 ,one operates as for sensitizing1 taking care to desiccate the paper1 as it has been directed4 ,the proofs are brilliant during the development1 but become dull in drying4 ,the paper not well sized4 ,it has been dried too slowly4 ,remember that it should be quite desiccated within fifteen minutes4 ,the paper is more or less yellow4 #ast4 ,the paper tinted with ultramarine4 #b;d4 ,the sensitizing solution or the developer are not sufficiently acid4 #c;d4 ,the washing 7fixing7 in the solution of hydrochloric acid was not sufficient to eliminate the iron salts from the paper4 ,the proofs harsh1 devoid of half tones4 #ast4 ,the sensitizing solution contains too much iron chlorate4 #b;d4 ,exposure too short4 ,the paper is stained4 ,the brush not kept clean while sensitizing4 ,black spots4 ,they are generally due to metallic dust in the paste of the paper1 or from particles of undissolved salt in the platinite solution4 ,,nb3 ,no good results can be expected unless the paper be kept absolutely dry before1 during and after exposure1 when using the former 7original7 process4 ,impaired sensitiveness of the paper1 want of vigor1 tinged whites1 muddiness1 indicate dampness4 ,,artigues' ,,process ,the ,artigues process1 so called1 is1 without any doubt1 the best to be employed for the reproduction of plans and drawings in lines4 ,it is simple1 expeditious1 and yields black impressions on a very pure white ground which are absolutely permanent4 ,and this is of the utmost importance when the copies are to be used for military purpose1 or kept in archives1 such as those of the ,patent ,office1 for example4 ,should it not require the use of negative clichs1 it would certainly supersede any of the processes previously described2 moreover1 as it will be seen1 it can be employed for many other purposes than that of obtaining duplicates from original drawings4 ,the objection is not even very great indeed1 for the design can be1 without great trouble1 transformed into a negative by the aniline method described in the beginning of this work4 ,the ,artigues process is an adaptation for the purposes in question of the carbon process invented by ,poitevin4 ,we shall describe it in extenso4 ,the paper can be prepared with any one of the following solutions3 #ast4 ,dissolve #b parts of ammonium bichromate and #e parts of best gum arabic in #ae parts of water and neutralize with a few drops of concentrated aqueous ammonia2 then add #ajj parts in volume of whites of egg and a certain quantity of thick ,india ink1 and1 this done1 beat the whole to a thick froth4 ,in ten or twelve hours the albumen will be deposited and ready for use4 ,the quantity of ,india ink added to the albumen should be such as the paper be black when coated1 but1 however1 sufficiently transparent for one to see the shadow of objects placed on the back of it1 and the coating should not be thick4 ,this is important in order to allow the light acting through the whole thickness of the preparation when the paper is insolated under the clich1 for1 if the film be too opaque or too thick 7by addition of too much gum arabic71 it would be only impressed on its surface1 and the image dissolved during the development4 ,the cause of this failure must be explained4 ,under the action of light the bichromate employed to sensitize the albumen is reduced into chromic oxide which render insoluble this organic substance--or any other1 such as caseine1 gelatine1 gum arabic1 etc42 therefore whenever the film is not acted on in its whole thickness1 the subjacent part being still soluble1 is necessary washed off and with it the superficial impressed part1 that is1 the image4 #b;d4 ,take #aj parts of lamp black and work it up in a mortar to the consistency of a thin paste by gradually pouring a little of a solution of from #f to #h parts of gum arabic and #a part of liquid glucose in #ajj parts of water1 adding afterwards the remainder1 into which #b parts of ammonium bichromate have been dissolved1 and filter through flannel4 ,with this1 coat the paper by brushing so as to form a thin and uniform film1 and pin it up to dry in the dark4 ,these solutions keep well for a certain period4 ,we have kept the albumen1 which we prefer to use1 for two months in good condition2 but the sensitive paper does not for more than three or four days in taking the usual care4 ,it is more practical--and this is recommended--to leave out the bichromate from the preparations1 and to coat the paper1 in quantity1 beforehand1 and for use to sensitize it with a solution of potassium bichromate at #c per cent4 of water applied on the verso with a ,buckle brush47#be7 ,the bichromate solution should be allowed to imbue the paper for about one minute1 and having brushed it once more1 the paper is pinned up to dry in the dark room4 ,it can also be sensitized from the back by floating1 if this manner is found more convenient4 ,when dry the paper is impressed under a negative clich of good intensity until the design1 well defined in all its details1 is visible on the back of the paper1 which requires an insolation of about two minutes in clear sunshine1 and from eight to ten times longer in the shade4 ,in cloudy weather the exposure to light is necessarily very long4 ,as explained before1 the luminous action1 by reducing the chromic salt in presence of certain organic substances1 causes the latter to become insoluble2 consequently if1 on its removal from the printing frame1 the proof be soaked in cold water1 for1 say1 ten minutes1 and1 placing it on a glass plate or a smooth board1 gently rubbed with a brush or a soft rag1 the parts of the albumen or gum arabic preparation not acted on will dissolve1 leaving behind the black image standing out on the white ground of the paper4 ,this done1 and when the unreduced bichromate is washed out in two changes of water1 the operation is at an end4 ,as to the theory of this and similar processes1 the insolubilization of the bichromate organic substance acted on by light was formerly attributed to the oxidation of the substance by the oxygen evolved during the reduction of the chromic salt into chromic oxide2 but from the fact that oxidation generally tends to destroy organic matters1 or to increase their solubility1 it is more probable that it results from the formation of a peculiar compound of the substance with chromic oxide 7,j4 ,w4 ,swan72 moreover1 gelatine imbued with an alkaline bichromate1 then immersed first in a solution of ferrous sulphate and afterwards in hot water1 is insolubilized with formation of chromium trioxide1 ,cr#b,o#g,k#b,,so#d;,fe ,,so#d,k#b;,c#b,o#d;,fe,c#b,o#c 7,monckhoven74 ,a similar but inverse action occurs1 as shown by ,poitevin1 when gelatine rendered insoluble by ferric chloride becomes soluble by the transformation1 under the influence of light1 of the ferric salt into one at the minimum4 ,the writer has improved the above process by simplifying the modus operandi as follows3 ,instead of compounding the preparation with gum arabic and the coloring matter1 the albumen is simply clarified by beating the whites of eggs to a froth1 etc41 and the paper is coated by floating for one minute1 then hung up to dry in a place free from dust4 ,if the reader has any objection for albumenizing his own paper1 he can use the albumen paper found in the market for the printing-out silver process generally employed by photographers4 ,the paper is sensitized from the back with the potassium bichromate bath by floating or by brushing4 ,when dry1 it is exposed as usual1 but for a shorter period than when the preparation contains the ,india ink or other coloring matters which impede the action of light4 ,the progress of the impression is followed by viewing1 from time to time1 the albumenized side of the paper4 ,when the design is visible1 well defined and brownish1 the proof1 being removed from the printing frame1 is rubbed with very finely powdered1 or1 better1 levigated graphite1 and1 this done1 immersed in cold water for from fifteen to twenty minutes1 when by gently rubbing it under a jet of water with a soft rag1 or with a sponge imbued with water1 the albumen is washed off from the parts not acted on1 leaving the design on a perfectly white ground4 ,if instead of graphite1 or any dry color insoluble in water1 lithographic ink1 much thinned with turpentine oil1 be applied on the print in a light coating which permits one to see the design under it1 and if1 then1 the print be soaked in water and afterwards developed as just directed1 an image in greasy ink is obtained4 ,and1 furthermore1 by replacing the printing by transfer ink1 one readily obtains a transfer ready for the stone or a zinc plate to be etched in the ordinary manner4 ,as usual there are two causes of failures in these processes1 viz41 under and over-exposures4 ,in the former case the image is partly washed off2 in the latter the ground cannot be cleared4 ,the reasons are obvious4 ,mr4 de ,saint ,florent gives the following processes37#bf7 ,a sheet of albumenized or gelatinized paper is sensitized from the verso on a solution of potassium bichromate1 dried in the dark and exposed under a positive clich4 ,after insolation1 the proof is washed in water1 to which are added few drops of ammonia1 then inked all over with an ink consisting of #ajj parts of liquid ,india ink1 #g parts of sulphuric acid and #c parts of caustic potassa1 and dried in a horizontal position4 ,when quite dry1 the proof is placed in water1 and after an immersion of about ten minutes1 rubbed with a soft brush3 the image little by little appears1 and if the time of exposure be right1 it is soon entirely cleared1 and1 then1 if not enough vigorous1 it may be inked again4 ,the gloss of the image is removed by means of a solution of caustic potassa at #aj per #ajj1 and the proof finally washed with care4 ,if in lieu of albumen paper1 one employs paper prepared with a thin coating of gelatine1 and dissolves the not acted on gelatine in warm water1 a very fine positive image is obtained by means of acidified inks which will fix themselves on the bare paper4 ,positive impressions from positive clichs can also be obtained in operating in the following manner3 ,on its removal from the printing frame the proof is washed1 sponged between sheets of blotting paper1 then covered with not acidified ,india ink mixed with potassium bichromate1 and1 when dry1 exposed from the verso to the action of light4 ,this done the image is cleared with a somewhat hard brush4 ,,the ,,carbon ,,process4 ,the carbon tissue is seldom prepared by photographers4 ,however1 for the sake of completeness1 we shall give the formula of the mixtures most generally employed1 and describe the manner of coating the paper on a small scale4 ,preparation of the ,tissue4--,the gelatine generally recommended to compound the mixture is the ,nelson's autotype gelatine4 ,coignet's gold label gelatine1 mixed with a more soluble product1 such as ,cox's gelatine1 for example1 gives also excellent results4 ,gelatine #aaj parts ,sugar #be parts ,soap1 dry #ab parts ,water #cej parts ,the coloring substances consist of3 ,,for ,,engraving ,,black4 ,lamp-black #bj parts ,crimson lake #b parts ,indigo #a part ,,for ,,warm ,,black4 ,lamp-black #c parts ,crimson lake #c parts ,burnt amber #b parts ,indigo #a part ,,for ,,sepia ,lamp-black #b parts ,sepia of ,cologne #ah parts ,,for ,,photographic ,,red ,,brown4 ,india ink #c parts ,crimson lake #d parts ,van ,dyck brown #d parts ,for blue1 ,turnbull's blue is employed2 for yellow1 light chrome yellow2 for red1 carmine dissolved in aqueous ammonia1 evaporating1 then adding water1 etc4 7,see further on47 ,to prepare the mixture1 dissolve the sugar and soap in the cold water1 add the gelatine1 let it soak for an hour1 then dissolve it in a water bath and mix by small quantity the colors finely ground together and wetted to the consistency of a paste4 ,after filtering through flannel the mixture is ready for use4 ,for coating1 the method devised by ,mr4 ,alf4 ,harman has been found excellent in the hands of the writer1 not only for the purpose in question1 but also for coating paper with gelatinous or viscous 7gum arabic7 preparations4 8,take two tin dishes1 such as used for the development of the carbon prints2 arrange one on your bench tilted to an angle2 the lower angle is intended to receive the warm water for keeping the gelatine mixture to a proper temperature4 ,into this angle of the tray arrange another tray somewhat smaller1 and keep it from touching the bottom of the outer one by the insertion of any small article that will suggest itself4 ,into the inner tray the gelatine mixture is to be poured40 8,the actual making of the tissue can now be proceeded with1 and is so simple and certain as not to be believed until put to the test4 ,purchase a roll of paper-hanger's lining paper of good quality1 cut it into widths of about one and a half inch less than the width of your inner tray1 and in length of1 say1 thirty inches4 ,for the success of the operation it is necessary that the paper be rolled up the narrow way4 ,now having just sufficient water at a temperature of #ajj deg4 ,fahr4 7#ch deg4 ,c47 into the outer tray1 pour the gelatine mixture into the inner one1 and take one of the lengths of rolled paper1 and1 holding it by both ends1 gently lower it on the surface of the gelatine2 then at once slowly raise the end of the paper1 which will unroll itself and become beautifully coated in far less time than it takes to describe4 ,twenty sheets may be coated in a quarter of an hour1 and be equal in all respects to that made by the most expensive machine40 ,in the description of this method of coating1 ,mr4 ,harman does not explain how the gelatine should be allowed to set before hanging up the paper to dry1 which is1 however1 obviously important4 ,it is as follows3 ,place on the tray a smooth board a little larger than the sheet of paper1 leaving a small space at the end furthest from the body1 and slowly1 without a stop1 draw off the paper1 prepared side uppermost1 on the board upon which it should remain until the gelatine is set4 ,if the paper curls up1 wet the back a little with a sponge before coating4 ,the following coating method1 due to ,mr4 ,chardon1 is excellent for sheets of paper of the ordinary photographic size1 #ahbb inches4 ,on a glass plate placed on a leveled stand1 is laid a sheet of paper previously wetted1 which is then flattened into contact with an ,india rubber squeegee1 taking care to remove the air bubbles interposed4 ,the quantity of gelatine necessary to coat the paper is regulated by means of a glass rod held by an iron lath1 which serves to handle it2 at each end of the rod is inserted a piece of an ,india rubber tube whose thickness regulates that of the gelatine layer4 ,the mixture is poured from a small teapot1 at the opening of which has been adapted a bent glass tube about three-sixteenths of an inch in diameter1 between the rod and the lath1 so that by a simultaneous motion1 one can equalize the gelatine as it is poured on4 ,when the gelatine is set the paper is hung up to dry4 ,in drying1 the gelatine contracts1 and1 necessarily1 causes a deformation of the tissue1 which curls up at the edges and loses its planimetry4 ,to prevent this1 while the gelatine is almost dry1 the tissue is placed under pressure until quite desiccated4 ,dumoulin advises to apply on the film1 while still soft and tacky1 a wooden frame1 which1 by adhering to it4 keeps the tissue perfectly plane as it dries4 ,chardon's method of coating ,sensitizing4--,the tissue is sensitized in a bath of potassium bichromate4 ,the degree of concentration of the bath1 which varies from #b to #e per cent4 of water1 is important4 ,the tissue sensitized in a weak bath is less rapidly acted on by light and yields more contrasts than when imbued in a concentrated one4 ,the former should consequently be employed for printing weak negatives1 and the latter for those which are intense4 ,a bath compounded with #cj parts of potassium bichromate1 #a1jjj parts of water and #b parts of aqueous ammonia1 is used for printing negatives of the ordinary intensity1 the tissue being1 then practically of the same sensitiveness1 a silvered paper insolated to obtain a print not over-exposed4 ,for intense negatives the ammonia should be discarded and replaced by the same quantity of chromic acid4 ,the time of immersion has also a certain influence on the results4 ,the less the tissue is allowed to absorb the solution the less sensitive it is1 but also the more the tendency of the half tints to be washed off during the development4 ,generally the tissue should remain immersed until it lies flat and the edges just commence to curl up1 unless white and black impressions are desired1 but even then it is preferable to operate as said above1 using a bath at #b per cent4 ,for use the bichromate bath should be cooled down to #ae deg4 ,c4 7#ei deg4 ,fahr471 and much lower in summer1 say #aj deg4 ,c4 7#ej deg4 ,fahr471 and kept at about this temperature by placing pieces of ice around the tray4 ,at #bj deg4 ,c4 7#fh deg4 ,fahr47 the prints are more or less granulated2 above this the gelatine is softened and the reticulation greater2 at #be deg4 ,c4 7#ge deg4 ,fahr47 it may dissolve4 ,the addition of alcohol to the bichromate bath--sometimes recommended to harden the film and allow it to stand a higher temperature1 and to hasten the desiccation of the tissue--is objectionable1 for the spirits tend to reduce the bichromate1 which is transformed into the green salt1 and1 therefore1 a partial or complete insolubilization of the gelatine is the result4 ,aqueous ammonia added to the sensitizing solution has for its object to permit one to keep the sensitive tissue for a somewhat longer period1 but it renders it less sensitive4 ,if enough be added to turn the solution yellow weak prints are obtained4 ,the bichromate bath should be renewed often4 ,it does not keep owing to the presence of gelatine and other organic matters which it dissolves and which cause the reduction of the chromic salt even in the dark4 ,the tissue prepared in such a bath is not very sensitive and the image develops with difficulty1 and even cannot be developed at all4 ,as said above1 the tissue is well sensitized when its edges commence to curl up4 ,it is then removed from the bath by drawing it on a glass rod fixed at the end of the tray1 and placed1 prepared side down1 on a slightly waxed glass plate1 rubbing it with an ,india rubber squeegee to remove the superflous liquid1 when it is hung up to dry4 ,while wet the bichromated tissue is insensitive2 the sensitizing can therefore be made by daylight1 but the drying should of course be done in the dark room1 that is in a room lighted by a candle or the sunlight filtered through a deep orange window glass4 ,caution4--,the soluble bichromates are very poisonous4 ,by absorption they produce skin diseases not without danger and very difficult to cure4 ,hence when handling the wet tissue the fingers should be protected by ,india rubber tips1 and any yellow1 stains on the hands should be rubbed with a dilute solution of aqueous ammonia1 and the hands well rinsed in water4 ,drying4--,when the tissue dries rapidly it adheres well on the support upon which it is applied for developing and yields brilliant images which are easily cleared4 ,on the other hand1 were it allowed to dry slowly the adherence would not be so complete1 the image dull and developing with difficulty4 ,they may even refuse to develop at all from the insolubilization of the gelatine4 ,in winter and in the cool days of spring and autumn1 the gelatine dries quick enough in the air1 but when the weather is warm and damp1 the gelatine1 drying very slowly1 may be so softened as to run off1 or to produce an entirely objectionable reticulation1 or the defects above mentioned4 ,this may be avoided by drying it pinned up in a box1 or a closet1 over quick-lime4 ,when dry1 the tissue is generally wrinkled1 brittle1 breaks easily in handling and cannot be laid flat on the clich2 but by holding it over a basin of boiling water1 the steam in a few moments rendering it sufficiently pliable to lay it flat between glass plates1 where it should be kept under pressure until wanted for use4 ,the writer always dries the tissue in the following manner1 which he devised about sixteen years ago47#bg7 ,and not only the least trace of reticulation is avoided1 but the tissue1 drying quite flat1 lies in perfect contact with the negative1 which is quite important to obtain proofs exactly sharp all over4 ,a clean glass plate is rubbed with talc1 or1 which the writer prefers1 flowed with a solution of7#bh7 ,yellow wax1 pure #a part ,benzine1 pure #ajj parts then strongly heated1 allowed to cool and rubbed clean 7apparently7 with a piece of flannel4 ,after once more repeating this operation the plate is coated with the following plain collodion37#bi7 ,ether1 conc4 #bej parts1 in volume ,alcohol1 #ie deg #bej parts1 in volume ,pyroxyline #c parts ,when the film is set1 the plate is immersed in filtered water until greasiness has disappeared1 when on its removal from the bichromate bath the tissue is laid1 without draining1 upon it and pressed into contact with the squeegee to remove the excess of liquid and1 with it1 the air bubbles interposited4 ,the tissue is then allowed to dry in the air on the collodionized plate in the cold season1 or1 when the weather is warm and damp1 in a box in the bottom of which is placed a quantity of quicklime in earthen dishes4 ,when dry1 the plates are placed one upon another1 wrapped in paper and kept in a dry place4 ,when wanted for use the tissue is stripped off and will be found quite flat with a beautiful surface to print upon4 ,one should avoid to keep the sensitized tissue in a moist and warm atmosphere1 for in less than ten hours it becomes insoluble even in complete darkness4 ,it should neither be kept in the air contaminated with gaseous reductive matters1 such as the products of the combustion of coal gas and petroleum1 sulphydric or sulphurous emanations from any source1 the fumes of turpentine oil1 etc41 which1 by reducing the chromic salt1 cause the insolubilization of gelatine1 prevent the print to adhere on the support or the clearing of the image1 which may even refuse to develop4 ,the sensitive tissue keeps well for three or four weeks in cool and dry weather1 and no more than eight or ten days in summer unless well desiccated and kept in a preservative box4 ,if kept too long the image cannot be developed4 ,the ,photometer4--,the time of exposure is regulated by means of a photometer4 ,of all the photometers which have been devised for that purpose we do not know any one more practical than that suggested in #ahgf by ,mr4 ,j4 ,loeffler1 of ,staten ,island4 ,it is made as follows3 ,on a strip of a thin glass plate1 #fb inches1 make four or five negatives1 #aa inch1 exposing each one exactly for the same period and developing in the usual manner1 but without any intensification whatever4 ,it is even advisable to reduce the intensity if they were opaque4 ,fix1 etc41 and apply a good hard varnish4 ,now cover the back of these negatives with strips of vegetable paper or transparent celluloid1 or1 better1 of thin sheets of mica1 in such a manner as there be one thickness on the second negative1 two on the third1 three on the fourth1 etc41 leaving the first one uncovered4 ,then place on the whole a glass plate of the same size as the first and border like a passe-partout4 ,the ,negatives4--,for the carbon process the negatives should be intenser than those intended for printing out on silver paper4 ,however1 good proofs may be obtained from any negatives1 so to say1 by varying the strength of the bichromate solution1 as1 also1 by using the tissue freshly sensitized for weak negatives1 in order to obtain vigor1 and for strong negatives1 the tissue two or three days after its preparation1 when it yields better half tones4 ,printing dodges are also resorted to4 ,that the most commonly employed consists to varnish the back of the negatives with a matt varnish1 or to stretch on the same a sheet of mineral paper upon which the retouches are made by rubbing graphite1 chrome yellow1 pink or blue colors to strengthen the shadows or the whites1 as the case requires4 ,as a rule1 it is advantageous to cover the printing frame with tissue paper1 whatever be the quality of the negatives4 ,the negatives should be bordered with deep yellow or orange-red paper to form what is termed a 8safe edge0 upon which should rest the tissue in order to prevent the margin from being insolubilized by the reductive action of light4 ,if this precaution were neglected it would be impossible to strip off the paper without tearing the proof when the tissue is applied on the support upon which the image is to be developed4 ,before exposing it is advisable to ascertain what the printing qualities of the negative are by making on silvered paper a proof of it--not over-printed--and another of the photometer1 both being exposed at the same time and for the same period4 ,this done1 compare the proof from the negative clich with those of the photometer1 and mark the negative with the number of that of the photometer to which it corresponds1 stating the shade of the proof next to it2 for example3 ,no4 #b2 ,no4 #c faint1 or commences to appear1 etc4 ,this ,no4 #b and the observation will indicate the intensity of the negative and serve as a guide for printing on the tissue1 since1 as before explained1 the silver paper is practically of the same sensitiveness as the tissue prepared for negatives of the ordinary intensity4 ,exposure4--,to print1 the tissue is laid over the negative1 taking care that it covers the safe edge1 and a strip of silvered paper placed in the photometer1 then both the printing frame and the photometer are exposed to light side by side4 ,unless the negative be weak1 when more vigor is obtained by exposing in sunshine1 the printing should be done in the shade4 ,it is a well-known fact that the part of the bichromated film corresponding to the half tones in the lights are not sufficiently impressed in comparison to the blacks while impressed in direct sun's light in this as well as in the collotype1 photogravure and other processes with the chromic salts1 because the luminous action through the bare glass1 or nearly so1 which in the negative represent the shadows and half blacks1 is more energetic in proportion than through the other parts1 from which it results that these parts being most acted on are made deeply insoluble through the thickness of the film1 and then require to be cleared by a treatment with water at a higher temperature than the parts representing the half tints in the lights of the picture1 which are but superficially and slightly insoluble1 can stand4 ,from time to time during the exposure the print in the photometer is examined1 and when a certain picture is printed to a certain shade1 or when the one next by commences to appear or is faintly printed1 etc41 the exposure of the tissue is sufficient4 ,this1 as the reader has already inferred1 is a matter of experience1 the guide being the knowledge of the intensity negative tested as above explained4 ,development4--,the carbon prints are developed either on a sheet of paper upon which it should remain 7single or simple transfer71 or on a provisory support to be afterwards transferred on paper or any other material 7double transfer74 ,simple ,transfer4--,this process is quite simple3 ,the impressed tissue and a sheet of paper coated with alumed 7insoluble7 gelatine are immersed face to face in cold water1 and when the tissue is softened both are removed1 one superposed on the other1 and the whole1 being placed on a glass plate and covered with a thin oil cloth1 is firmly pressed into contact with the squeegee4 ,the rationale of applying under water the tissue on the gelatinized paper is to avoid the interposition of air bubbles4 ,to operate by simple transfer the tissue should be impressed under a reversed negative4 ,the reason is obvious4 ,double ,transfer4--,by this method the carbon prints are generally developed on porcelain or opal plates1 which more easily than glass plates permit one to follow the progress of the development and to retouch the imperfections before transferring the picture on paper4 ,in order that the image does not adhere on the provisory support a little of the following mixture is spread over the plate1 which is then pretty strongly heated1 and1 when it has cooled down1 polished lightly with a piece of white flannel to obtain a very thin and even layer free from stri4 ,if the plate has not been used before for the purpose in question1 it should be waxed a second time in the same manner3 ,yellow wax #d parts ,rosin #a part ,turpentine or benzine #bej parts ,the plates can be developed on the plates so waxed1 but for 8full gloss10 that is1 for enameled pictures1 a film of collodion is applied on the plates1 which then1 instead of being waxed1 should to be simply flowed with a solution of ,india rubber #a to #ajj of benzole3 ,ether #bej parts ,alcohol #bej parts ,castor oil #a part ,pyroxyline #e to #f parts ,when the plate is coated and the collodion film set1 it is immersed in water until greasiness has disappeared and wanted for use4 ,then the tissue1 previously soaked in water1 is applied upon it 7taking care to avoid air bubbles7 and squeezed1 lightly at first1 with some force afterwards1 to insure a perfect contact4 ,zinc plates are also employed as provisory supports instead of glass1 opal or porcelain plates4 ,the modus operandi is exactly the same47#cj7 ,the plates should be well planed1 free from scratches1 etc41 and well polished to obtain glossy pictures without one having recourse to a film of collodion4 ,for matt pictures1 i4e41 without gloss whatever1 the plate should be finely granulated1 and when waxing a very light pressure should be exerted to remove the excess of wax1 else it might be quite impossible to strip off the picture in transferring on paper4 ,for double transfer on biscuits1 objects in alabaster1 porcelain1 wood1 any even or curved rigid materials1 flexible supports are employed to develop the pictures4 ,these supports are prepared by fastening albumen paper on a board and evenly brushing over the following hot compound1 filtered through flannel1 which1 when dry1 is polished with a cloth3 ,stearine #ae parts ,rosin #c parts ,alcohol #ajj parts ,the flexible supports should be waxed1 then collodionized for full gloss1 as the glass1 porcelain and metallic plates4 ,another method which the writer recommends is the following1 due to ,mr4 ,swan3 ,immerse a sheet of paper in a solution of ,india rubber1 #d3ajj of benzole1 and let dry1 which requires a few minutes4 ,this is the flexible support4 ,then after exposure1 brush over the ,india rubber solution on the carbon tissue1 apply upon it the support when the benzole is evaporated1 and pass the whole under a rolling press to secure adhesion1 then develop4 ,to transfer1 soak the proof in tepid water1 apply it on the material prepared1 as it will be explained further on1 and when dry1 imbue the support from the back with benzole1 to soften the ,india rubber1 and strip4 ,to dispense with a rolling press1 the proof may be developed on lacquered vegetable paper prepared by immersion in a solution of #aj parts of red shellac in #ajj parts of alcohol4 ,after developing the proof is coated with alumed gelatine1 and when dry transferred as usual4 ,to strip off it suffices to imbue the paper with alcohol in order to dissolve the shellac4 ,when the picture must be transferred on small spaces or on small objects the most simple method--the most effective1 perhaps--is the following1 devised some years ago by the writer and now employed for the ornaments of 8articles de ,paris30 ,prepare the provisory support as usual1 but with a thicker film of collodion2 then1 after developing and coloring1 if necessary1 the picture is coated with gelatine1 to which may be added some zinc white or other colored substance to form a ground4 ,this dry1 strip off1 immerse the pellicle in water to soften the gelatine and transfer on the material collodion side up4 ,the proofs should be developed within three or four hours after insolation1 for the luminons action continues pretty actively in the dark1 and this for a long time2 thus3 a proof rightly exposed in the morning behaves as one over-exposed if developed in the evening1 and after a certain period either can not be developed or refuses to adhere on the support4 ,however1 the proofs can be kept for three weeks1 may be more1 before development1 if the soluble bichromate be washed off1 the tissue sponged and dried rapidly in the warm season4 ,this capital improvement is due to ,mr4 ,charles ,brasseur4 ,it has been said that before being applied on the support the proof should be immersed in water to soften the tissue4 ,the time which it should be allowed to absorb water has an importance which must not be neglected4 ,if it do not remain long enough to be soaked through1 small invisible air bubbles are formed on its surface1 and interposing themselves between the image and the support1 form minute1 brilliant1 silver-like spots on the finished picture2 and1 if the temperature of the water is above #bj deg4 ,c4 7#fh deg4 ,fahr471 the image will be more or less reticulated4 ,the temperature depends a good deal of the softness of the gelatine2 #ae deg4 ,c4 7#ei deg4 ,fahr47 is safe1 except1 however1 when the thermometer is in the thirtieths 7#ijth ,fahr471 when the water should be cooled down a few degrees lower1 but not at the melting ice temperature1 for then the proof would not adhere well4 ,as a rule1 the tissue should remain in the cold water until it becomes flat and shows a tendency to curl up4 ,it is at this very moment that it should be squeezed on the support4 ,the proofs should not be developed immediately after transferring4 ,the adherence is greater and the pictures finer and devoid of defects when the development is made half an hour1 and even an hour1 after4 ,if developed too soon the picture will be partly1 and even entirely1 washed off4 ,hence1 a number of transfers can be prepared beforehand1 placing them1 face to face one upon another1 in order that the tissue does not dry1 which is quite essential4 ,to develop1 the plate1 with the tissue adhering to it1 is placed in water heated to #cj deg4 ,c4 7#hj deg4 ,fahr471 where it is left rocking the tray occasionally until the paper rises up by itself at the corners1 when taking hold of it by one corner1 it is stripped off1 leaving behind the image buried in soluble gelatine4 ,should the paper offer any resistance whatever1 the gelatine should be allowed to become more soluble by increasing the temperature of the water1 or by a longer immersion4 ,there is1 in fact1 no objection to this4 ,the plate--and that is a good method--can be placed in an upright position in a tin box1 made ad hoc1 and left therein in warm water until the paper detaches itself and the image is partly developed and the bichromate washed off4 ,this done1 the plate is held in an inclined position on a tray filled with water at #ce deg4 ,c4 7#ie deg4 ,fahr471 which is dashed with a wooden spoon on the image to clear it from the non-acted-on gelatine4 ,presently one can judge whether the exposure is right4 ,if it is too short1 the half tints in the shadows are washed off1 unless the negative be too intense1 when a similar effect also occurs in the whites4 ,if it is too long1 either the image is with difficulty cleared or remains undeveloped4 ,in the latter case1 it is recommended by some operators to increase the temperature of the developing water to near the boiling point1 and1 for local clearing1 to pour it on4 ,this we find objectionable1 for the half tints are easily washed off4 ,a better process1 when the picture can not be cleared by water at #ej deg4 7#abb deg4 ,fahr471 or thereabout1 is to use a solution of common salt at #e or #f per cent4 of slightly warm water47#ca7 ,it is even preferable to finish the development in a tepid solution of potassium sulpho-cyanide1 #ab3ajj4 ,the dissolving action is long1 but not only1 as said above1 the half tints are best preserved1 but blistering and local washing-off are avoided4 ,after development the plate is rinsed under the tap1 then flowed two or three times with a solution of chrome alum at #a per cent4 of water1 then washed1 and finally allowed to dry spontaneously4 ,it is objectionable to use a strong solution of alum1 and in it to immerse the plate for any length of time2 the gelatine is considerably hardened--which is not necessary--and more liable to crack by time in being thoroughly desiccated4 ,we discard the common alum which we found liable to produce a slight reticulation4 ,two defects are complained of by the beginners1 viz41 the want of adherence of the deep blacks1 and1 especially1 the isolated and fine lines when the picture is a reproduction of an engraving1 a drawing1 etc41 and the liability in half tone pictures of the delicate details being washed out4 ,the first defects are avoided by pouring a solution of boric acid on the transitory support before applying the tissue and developing at a low temperature with salted water4 ,the second from an imperfect knowledge of the properties of gelatine acted on by light in presence of a salt of chromic acid4 ,one should bear in mind that the degree of solubility of gelatine so acted on1 as also its degree of impermeability--which is important in certain processes of photogravure--is proportionate to the degree of insolation2 thus1 when not impressed1 bichromated gelatine dissolves in water heated to about from #be to #cj deg4 ,c4 7#gg to #hj deg4 ,fahr471 and when acted on between #cj and #ajj deg4 ,c4 7#hf to #aab deg4 ,fahr471 according as to the degree of insolation1 that is1 of reduction of the chromic salt1 the latter temperature being that of insolubility of the parts the most acted on4 ,the very delicate half tints do not1 generally1 stand a temperature higher than #ce deg4 ,c4 7#ie deg4 ,fahr471 and1 therefore1 as the degree of insolubility of the various parts cannot be ascertained1 a priori1 it is advisable during the development to increase gradually the temperature of the water from this degree1 and not to exceed #de deg4 ,c4 7#aac deg4 ,fahr471 in order to obtain the most perfect result from a negative of good intensity4 ,indeed1 by placing the supports on a rack and immersing the whole in water heated to #cj to #ce deg4 ,c4 7#hf to #ie deg4 ,fahr471 the image will clear up by itself to perfection in a certain period4 ,this method is excellent for proofs in lines4 ,those from the grained negatives employed in photogravure are still more perfectly developed in a tepid solution of potassium sulphocyanate1 since the impressions wholly consist of insoluble parts 7the lines7 and gelatine not acted on4 ,retouching4--,the retouches are easily made4 ,they should be done before transferring when working by the double transfer process4 ,the transparent spots1 and any parts which should be altered1 are retouched with the material of the tissue dissolved in warm water2 the whites are cleared with a scraper2 and any parts which are not intense enough1 or which should be blended by the addition of half tints1 are worked on the proof--to which a tooth has been given by rubbing with cuttle-fish powder--by means of a stump and an appropriate color1 a mixture of lamp-black and carmine1 for example1 in very fine powder4 ,the proofs can also be colored by chemical means 7see further on71 or with water colors employed with a solution of chrome alum1 #a to #bjj of water1 or gilt1 silvered or bronzed with metallic powders applied with the gilder's size thinned with turpentine on the proof previously coated with a thin layer of alumed gelatine4 ,second ,transfer4--,to transfer1 a sheet of enameled or simple transfer paper is immersed in tepid water until the gelatine is softened and feels slippery to the fingers4 ,the support is then placed under water at ordinary temperatures--not under #af deg4 ,c4 7#fj deg4 ,f47--for two three minutes1 then rubbed with a camel brush to remove the air bubbles1 which might be formed on the surface of the image1 when1 without draining1 the gelatinized paper is laid upon it1 covered with the thin oil cloth1 and pressed into contact with the squeegee1 commencing in the center to the sweep off the water1 then repeating the operation for the other half1 as explained to apply the tissue on the provisory support4 ,when the whole is quite dry1 which requires three or four hours1 the edges are cut with a penknife and the whole stripped off4 ,it may happen that the proof is covered with minute1 silver-like brilliant spots1 which are nothing else than very small air bubbles interposited between the carbon proof and the transfer paper4 ,they are caused by the gelatine paper not having been sufficiently softened or not laid on the proof with proper care4 ,the defect may also arise from the transfer paper coated with not sufficiently thick gelatine4 ,to transfer on any rigid material1 the proofs on flexible supports are coated by floating on the following gelatine solution1 then allowed to dry1 and1 when wanted for use1 immersed in tepid water to soften the gelatine and secure adherence3 ,gelatine #ej parts ,water #djj parts ,solution of chrome alum1 #f parts #d3ajj ,development on ,absorbing ,materials4--,the development of carbon prints on absorbent material--such as canvas and palettes to be painted in oil1 etc4--cannot be made in the ordinary manner on account of the impossibility to eliminate entirely the chromic salt which tinges the material yellow4 ,to turn the difficulty1 it suffices to wash off in several changes of cold water all the unaltered bichromate from the prints on their removal from the printing frame1 and to proceed as usual1 or the prints can be allowed to dry and transferred at some future time4 ,canvas should be prepared by brushing with a solution of aqueous ammonia in alcohol1 #e3bj1 to remove greasiness until the thread is apparent1 and1 when dry1 rubbed with sand to grain it--or to give a tooth1 as it is termed--then rubbed dry with a solution of soluble glass1 #a to #aj of beer47#cb7 ,palettes should be rendered impervious1 or nearly so1 by flowing upon them a solution of alumed gelatine1 which is allowed to penetrate into the pores of the wood and the excess scraped off when solidified1 when the surface may be whitened1 if necessary1 as for printing on wood box1 q4v4 ,opals1 porcelain1 or ivory should be prepared with the following substratum3 ,gelatine #ej parts ,water #djj parts ,chrome alum1 #d3ajj #f parts ,very fine carbon proofs having the appearance of pictures on opal plates are made by transferring in the following manner1 devised by the author3 ,develop on the ground surface of a glass or porcelain plate1 well waxed1 to obtain a matt picture1 or in the ordinary manner for full gloss1 and when the image is retouched or colored1 apply a thin coating of gelatine1 let dry and coat with the following opaque collodion3 ,a4 ,ether1 conc4 #ajj parts ,alcohol1 #ie deg #ij parts ,pyroxyline #g parts ,b4 ,white zinc in very #i parts fine powder ,castor oil #c parts ,alcohol #aj parts ,grind in a mortar1 adding ultramarine blue and carmine1 or a little of any suitable coloring matters1 and mix to ,a4 ,when the collodion is dry1 which requires a few hours1 strip the whole or back with strong white or colored paper before stripping4 ,a solution of gelatine with glycerine1 white zinc1 etc41 may be substituted for collodion when the pictures are employed as ornaments on wood1 etc4 ,carbon prints on celluloid are now made for similar purposes4 ,,opal ,,gelatine ,,solution ,gelatine #aej parts ,glycerine #ae parts ,zinc1 white #dj parts ,water #fjj parts ,to which some coloring matters may be added according to taste4 ,grind the white with the glycerine and a little water1 mix to the gelatine dissolved in the remainder of water1 and filter through canvas4 ,apply the mixture moderately hot1 #cj deg4 ,c4 7#hf deg4 ,fahr47 ,transparencies4--,the transparencies are printed on a special tissue sold under the name of 8diapositive40 ,it differs from the ordinary tissue in this1 that the mixture contains a greater quantity of the color matter1 ,india ink1 which is ground exceedingly fine4 ,the proofs for transparencies should be printed deeper than those to be seen by reflection1 and developed on thin glass plates1 free from any defects1 and coated with either one of the following substrata3 ,soluble glass #e parts ,white of eggs #ae parts ,water #bj parts ,the whole is beaten up to a thick froth and allowed to subside1 when the clear liquid is decanted1 filtered through flannel and the glass plates coated4 ,the substratum should be allowed to dry for a few hours1 and rinsed under the tap before use4 ,the other substratum consists of ,gelatine #ce parts ,acetic acid1 ,no4 #h #bej parts ,alcohol1 #ie deg #ej parts ,water #gjj parts ,chrome alum1 #d3ajj #fj parts ,dissolve the gelatine in the acid at a moderate heat1 add afterwards the alcohol and water1 and lastly mix the chrome alum by small quantities at a time4 ,these substrata are employed to avoid the peeling off of the image4 ,to prevent the entire desiccation of the gelatine1 which is the cause of the defect above alluded to1 it is advisable to add glycerine to the washing water after the image is cleared4 ,some operators recommend a coating of flexible collodion1 that is1 prepared with castor oil1 for the purpose in question4 ,we do not think that necessary when the transparencies are not exposed to sunshine4 ,if anything should be applied we would prefer the encaustic4 ,carbon transparencies are invaluable for reproducing negatives in the original size by the same 7carbon7 process1 or for enlarging by the collodion or gelatine process4 ,for these purposes they should be made on the special red tissue manufactured by the ,autotype ,company1 of ,london1 ,eng4 ,they can1 however1 be made on the ordinary tissues4 ,whatever be the tissue employed1 the transparencies for the reproduction of negatives are seldom opaque enough1 and should be intensified4 ,this is done by treating them with a very dilute solution of sodium permanganate1 which colors them olive green4 ,transparencies for lantern slides1 etc41 are best colored with the couleurs l'albumine of ,l4 ,encausse1 sold by ,j4 ,reygondaud1 ,paris 7,france74 ,they are transparent47#cc7 ,toning and ,intensifying4--,the carbon proofs can be toned and at the same time intensified by reagents acting with chromic oxide4 ,the dyes or coloring matters precipitated are not opaque1 and1 as a consequence1 not objectionable for transparencies4 ,the following processes are the most employed3 ,prepare three solutions as follows3 ,a4 ,ferric sulphate #e parts ,water #ajj parts ,b4 ,sodium carbonate #b parts ,water #ajj parts ,c4 ,gallic acid #e parts ,water #ajj parts ,dissolve the gallic acid in warm water4 ,filter each solution4 ,they keep well4 ,to tone1 the plate is immersed for1 say1 ten minutes in ,a1 then1 after rinsing slightly1 it is placed in ,b for the same period1 rinsed again and flowed with ,c until the desired color is obtained4 ,the tone is a splendid purple black color4 ,if a solution of pyrogallol be substituted to that of gallic acid1 the tone is green1 and to a green bordering to black when a solution of catechu is used1 the catechu exerting at the same time a tanning action on the gelatine4 ,after toning1 the plate should be thoroughly washed4 ,a similar process consists to wet the plate under the tap1 then to flow over a mixture by about equal volumes of ,a4 ,ferrous sulphate #e parts ,acetic acid1 ,no4 #h #e parts ,water #ajj parts1 filter ,b4 ,gallic acid #e parts ,water #ajj parts ,when toned1 the plate is well washed1 then flowed once with the alum solution and again washed4 ,the tone by this process easily turns to an inky blue not very agreeable4 ,the action should be stopped a little before the desired color is obtained4 ,it sometimes happens that the image in drying intensifies more then necessary4 ,it can be cleared with a solution of oxalic or citric acid4 ,a brown sepia is obtained by toning first with potassium permanganate1 #a per cent4 of water1 then1 after washing1 with a solution of pyrogallol4 ,if gallic acid be used instead of pyrogallol1 the tone is black4 ,by this process a great intensity is obtained4 ,a dilute solution of ammonium sulphide can be employed as a clearing agent4 ,pyrogallol and silver nitrate give a warm black tone4 ,potassium bichromate followed by silver nitrate form a brick-red precipitate of some opacity47#cd7 ,chloride of nickel and potassium ferrocyanate produce a fine brown4 ,lime water and alizarine dissolved in alcohol dye violet4 ,alizarine and the caustic alkalies produce a variety of tints1 from violet to purple1 according to the concentration of the solutions4 ,lead acetate and alizarine in ammoniacal solution dye purple4 ,potassium ferrocyanide and uranium nitrate produce a warm sepia tone4 ,with chloride of nickel the tone is brown4 ,ammoniacal solution of coralline diluted with water gives carmine red4 ,potassium bichromate and extract of indigo produce a fine greenish tone suitable for landscapes4 ,extract of indigo colors blue7#ce7 ,some of these reactions can be applied to the printing processes with the bichromates1 etc4 ,the paper should be coated with galatine4 ,see the ,appendix4 ,other colorations can be obtained with dyes in utilizing 7as shown by ,persoz7 chromous chromic oxide as a mordant3 alizarine1 ,brazil and yellow wood 7morus tinctoria71 ,fustet 7rhus cotinus71 etc4 ,the extent of this work does not admit of describing the numerous processes which can be employed2 they will suggest themselves to the chemist4 ,the alkalies employed with the dyes should be employed in diluted solutions1 as being liable to produce reticulation4 ,by applying the coloring matters and the mordants thickened with a little starch1 the image can be colored with different colors4 ,lantern slides can be thus colored with great ease4 ,,preparation ,,of ,,red1 ,,yellow1 ,,or ,,blue ,,tissues4 ,red ,tissue4--,dissolve #aj grams of carmine in #a liter of aqueous ammonia and evaporate4 ,when the smell of the alkali has almost disappeared1 add #a liter of rain water4 ,of this take #fe cubic centimeters1 add #ce c4c4m4 of rain water1 and in the solution let soak for an hour #ae grams of very soluble gelatine1 add #a gram of sugar1 and dissolve in a water bath4 ,filter1 and take of the mixture a sufficient quantity 7#be c4c4m4 for a surface #ahbd centimeters7 to cover a sheet of paper which has been previously applied upon a glass plate in the following manner3 ,in a tray full of hot water1 immerse the plate and the paper2 remove the whole in such a manner as the paper remains in contact with the plate2 rub out the excess of water with a squeegee1 and flow the gelatine over the paper still damp4 ,let cool on a leveled stand1 and when the gelatine is solidified to a consistent jelly1 remove the paper from the plate and place it to dry in an oven heated at not over #bd or #be deg4 ,c4 ,it is desirable that in drying the paper does not curl up4 ,to that end1 apply over it1 before it being removed from the plate a wooden frame to which the gelatine1 still sticky1 will sufficiently adhere to hold the tissue when it stretches in drying4 ,yellow ,tissue4--,pulverize to an impalpable powder #be grams of light chrome yellow in tablets 7water color71 and gradually add in stirring #a liter of rain water4 ,take #ajj c4c4m4 of this and into it let soak for an hour #ae grams of the same gelatine used for the red tissue1 add #a gram of sugar1 then proceed as above4 ,blue ,tissue4--,in a liquid consisting of #he c4c4m4 of rain water and from #ab to #ae c4c4m4 of blue ink1 such as sold by stationers1 let soak for an hour #ae grams of the same gelatine and #a gram of sugar1 and proceed4 ,preparation of ,transfer ,paper4--,two kinds of transfer paper are employed--the enamel and plain transfer paper4 ,to enamel the paper3 ,dissolve #ajj parts of barium nitrate in #ejj parts of water1 and1 on the other hand1 #bjj parts of sodium sulphate in the same quantity of water4 ,mix1 wash well the precipitate--barium sulphate--by decantation1 and when well drained1 mix to the following solution3 ,gelatine1 ,coignet's #cjj parts ,glycerine #hj parts ,ultramarine blue #a part ,crimson lake #j4a part ,water #b1ejj parts ,let soak the gelatine for1 say1 one hour1 dissolve by heat1 then add by small quantities1 stirring violently1 #d parts of chrome alum dissolved in #bej parts of hot water4 ,filter through flannel and coat the paper as directed to prepare the tissue4 ,the mixture should be employed immediately after adding the chrome alum4 ,the plain transfer paper is prepared in the same manner1 leaving out the barium sulphate and the coloring matters4 ,preparation of the ,silver ,paper4--,immerse the paper for two minutes in a solution of-- ,sodium chloride 7common #b parts salt1 dry7 ,lemon juice #a part ,water #ajj parts 7filter7 ,when dry and wanted for use1 sensitize the salted paper by floating for one minute on-- ,silver nitrate #h parts ,nitric acid #j4a part ,water #ajj parts ,on its removal from the silver bath1 sponge the paper between sheets of blotting paper and hang it up to dry4 ,,encaustic ,,for ,,single ,,transfer ,,proofs4 ,white wax #be parts ,mastic #c parts ,turpentine #ajj parts ,dissolve by heat1 first the mastic1 then the wax1 and keep for use in a large mouthed vial4 ,,matt ,,varnish4 ,sandarac #f parts ,mastic #f parts ,lavender oil4 #j4e parts ,ether #ajj parts ,when dissolved1 add #cj parts of benzine4 ,the opacity of the film varies with the quantity of benzine added2 by excess the varnish dries transparent4 ,,water ,,colors ,,which ,,resist ,,the ,,action ,,of ,,light4 ,red4 ,indian red4 ,light red4 ,orange4 ,mars yellow4 ,blue4 ,cobalt blue4 ,french blue4 ,smalt4 ,new blue4 ,brown4 ,raw umber4 ,burnt sienna4 ,green ,terre verte4 ,yellow4 ,cadmium ,yellow ,roman ochre4 yellow4 ochre4 ,,appendix4 ,although we intended to only describe the printing processes without the use of silver salts1 we thought it would be well to complete this work by giving the most practical and interesting processes ever published to obtain permanent photographs2 as they may give rise in the hand of experimenters to useful applications4 ,from time to time processes are published under 8queer0 names1 which are based on the well known actions of reagents on the ferric salts reduced by light4 ,they are derived from those described in the following pages4 ,we call specially the attention of the reader to the process of ,poitevin1 by which one can experiment with every ferric salts1 citrate1 lactate1 oxalate1 tartrate1 benzoate1 etc41 by simply exciting with the corresponding acid4 ,observe that to obtain good results the paper should be strongly sized2 it is a sine qua non1 although not recommended by ,poitevin4 ,c4,j4 ,,burnett',s ,,process7#aheg74 8,a capital process for many purposes10 says ,mr4 ,burnett1 8is to float or steep the paper in a mixed solution of bichromate of potash and sulphate of copper1 as for ,hunt's chromotype process47#cf7 ,i have mixed gelatine1 or occasionally grape sugar1 or both with the solution27#cg7 but instead of developing it with nitrate of silver1 as in chromotype1 wash out the salt unaltered by light1 and develop by floating on a solution of ferrocyanate of potassium4 ,the purple red color of the copper salt which now forms the picture may be modified or changed in many ways17#ch7 viz41 by soaking the picture1 after the ferrocyanate of potassium has been washed out of the lights1 in a solution of sulphate of iron4 ,solutions of gallic acid1 tannic acid with alkalies of carbonate1 may also be employed to modify or change the color4 ,this process has the advantage that one may regulate the exact tone 7black or useful neutral tint7 to the greatest nicety by the time we allow the print to remain in the iron toning bath40 ,,godefroy',s ,,process 7#aheh74 ,float the paper upon the following solution for three minutes and hang it up to dry3 ,uranium nitrate #cj to #fj parts ,silver nitrate #h parts ,water #ajj parts 7#ci7 ,the sensitiveness increases in proportion to the quantity of uranium nitrate4 ,with the above formula the paper can be exposed in the camera1 or1 for printing1 under a negative clich4 ,in printing an exposure of five seconds in diffused light gives an image perfectly visible1 and a grayish black tone2 ten seconds gives a vigorous image almost of a black color2 in from fifteen to twenty seconds the image is very strong1 with the color of an engraving4 ,in sunshine the action is necessarily much more rapid4 ,the impression is developed by immersion in ,ferrous sulphate #h parts ,tartaric acid #d parts ,sulphuric acid #a part ,water #ajj parts ,the image is rapidly developed4 ,it is fixed by washing in water4 ,,de ,,la ,,blanchere',s ,,process 7#aheh74 ,uranium nitrate #be parts ,distilled water #ajj parts ,filter the solution and keep it in the dark4 ,the paper should be sized with a gelatine solution at #e per #ajj of water1 and1 when dry1 kept in the dark47#dj7 ,it is sensitized by floating five minutes4 ,the exposure under a negative varies from fifteen to twenty minutes in the shade1 and from one to three minutes1 at the most1 in sunshine4 ,as a rule1 it is advisable to somewhat underexpose in order that the development be regular1 progressive1 under control4 ,the image is developed by floating1 or immersion in ,silver nitrate #b parts ,distilled water #ajj parts ,nitrate acid1 ,c4,p4 a trace ,when the image is intense enough it is washed in several changes of water1 then toned in a solution of gold at #a per #a1jjj of water acidified with traces of hydrochloride acid47#da7 ,the following bath develops slowly1 and gives very rich purple tones without toning3 ,nitrate of silver #c parts ,nitrate of uranium #a part ,nitrate of cadmium #a part ,alcohol #aj parts ,water #ajj parts ,nitric acid traces ,the developing solutions should be as little acid as possible1 but not neutral1 for then the proofs would be veiled and grayish4 ,the image can also be developed in a solution of gold1 or in a very weak solution of mercuric chloride at #a per #aj1jjj4 ,the proof must be extremely well printed and left for from two to five minutes in the mercuric solution4 ,if the time of exposure is right1 the image will change but little in the solution1 and will take1 when treated with silver nitrate1 the most splendid tones4 ,the proofs should be carefully washed when finished4 ,if they were developed with silver1 they must be immersed in diluted aqueous ammonia1 which will perfectly clear the whites4 ,if developed with chloride of gold1 the water should be heated to #fj to #hj deg4 ,c4 7#adj to #agf deg4 ,fahr47 ,,houdoy',s ,,process 7#aheh47 ,the paper is floated upon a lukewarm solution of gelatine at #e3ajj1 and when dry1 on a bath of uranium at #aj or #ae per #ajj of water4 ,after exposure to the sun the image is developed with a solution of silver nitrate acidified with acetic acid4 ,the exposure varies1 according to the nature of the negative1 from one to ten minutes2 it must be long enough for the image being developed in from thirty to forty seconds4 ,it is then removed from the silver bath and placed in the following3 ,ferrous sulphate #c to #h parts ,acetic acid #b parts ,water #ajj parts ,in this bath the image takes a great vigor and appears entirely on the surface of the paper4 ,when the proof has been too long exposed it should be washed slightly before placing it in the iron bath4 ,developed1 the image is1 generally1 of a sepia tone1 which can be turned to black by a solution of chloride of gold1 #a3a1jjj1 washing afterwards as usual4 ,,ni,,pce ,,de ,,st4 ,,victor',s ,,process 7#ahei74 ,red ,prints4 ,float the paper for fifteen or twenty seconds on a #bj per cent4 solution of nitrate of uranium and dry before the fire in the dark room4 ,this paper can be prepared many days before use4 ,expose in sunshine from eight to ten minutes1 according to the intensity of the light and the quality of the negative1 then wash in moderately warm water 7#ej to #fj deg4 ,c47 for a few seconds4 ,this done1 immerse in a solution of red prussiate of potash at #b per cent4 of water2 in a few moments the proof will become of a fine blood-red color1 like 8sanguine40 ,wash1 etc4 ,green ,prints4 ,make a red print as above described1 immerse it for a few minutes in a solution of nitrate of cobalt and dry it without washing4 ,fix then in a solution of sulphate of iron at #bj per cent4 of water and #d of sulphuric acid4 ,wash and dry before the fire4 ,violet ,prints4 ,prepare the paper in the uranium bath1 expose1 wash and develop in a solution of chloride of gold1 #a3bjj1 until the proof has assumed a fine violet color4 ,wash in several changes of water4 ,blue ,prints4 ,sensitize the paper with a red prussiate of potash solution at #bj per #ajj4 ,let dry1 expose until the proof is slightly blue2 immerse it for five or ten seconds in a saturated solution of bichloride of mercury1 wash only once and immerse in a solution of oxalic acid--saturated when cold--heated to about #ee deg4 ,c4 ,wash in three or four waters and let dry spontaneously4 ,black ,prints4 ,float the paper on a mixture by equal volumes of a solution of iron perchloride and another of uranium nitrate1 each at #aj per #ajj of water4 ,expose and develop on a saturated solution of gallic acid4 ,,dr4 ,t4,l4 ,,phipson',s ,,process 7#ahfa74 ,take a solution of perchloride of iron and1 having precipitated the peroxide with ammonia1 collect the precipitate on a filter and wash it with boiling water4 ,add the precipitate in excess to a warm solution of oxalic acid4 ,a beautiful emerald green solution is obtained1 which must be a little concentrated by evaporation and then set aside in a dark room for use4 ,the paper is floated for ten 787 minutes upon the green solution of ferric oxalate1 to which has been added a little oxalate of ammonia and hung up to dry in the dark4 ,expose under a negative for from ten to twenty minutes1 according to the weather1 and wash well the paper with rain water4 ,spring water will not do on account of the lime it may contain1 which will form oxalate of lime in the paper 7insoluble74 ,when all the non-decomposed oxalate is washed from the proof1 a feeble image of oxalate of protoxide of iron1 scarcely visible1 is left on the paper4 ,to develop it and to obtain the vigor1 the tone and color of silver prints proceed as follows3 ,plunge the proof for a little while in a 7weak7 solution of permanganate of potassium to which a few drops of ammonia have been added2 in the bath the image becomes brown and distinctly visible4 ,it is then withdrawn and immersed in a solution of pyrogallic acid for half an hour1 after which it is washed and dried4 ,the image thus obtained can hardly be distinguished from silver prints2 the tone is soft1 brilliant and permanent4 ,this process is quite original and interesting4 ,the theory is as follows3 ,under the action of light the ferric oxalate is reduced in the ferrous salt1 insoluble1 which1 after the print has been cleared from the ferric oxalate1 is oxidized and reduced into ferric oxide by the alkalized permanganate1 the latter then forming colored compounds with reagents4 ,it has been lately published in ,england under the name of 8kallitype10 a new process--or old1 ad libitum--which consists in developing the image in ferrous oxalate by a peculiar silver compound whose formula is given below4 ,the paper is prepared by brushing with a strong solution of neutral ferric oxalate dried rapidly--which is a sine qua non when using deliquescent salts2 and after exposure the image is developed1 etc4 ,silver nitrate #ej grains ,sodium citrate #hjj grains ,potassium bichromate #a to #b grains ,water #aj ounces 8,dissolve the silver nitrate in #a ounce of water1 the citrate and bichromate in the remainder and mix4 ,the precipitate--silver citrate and chromate--is then dissolved by adding #a dram of ammonia 4#hhj1 and after #ce drops of strong nitric acid has been added the solution is ready for use40 ,this process reminds us that of ,robert ,hunt 7#ahdb71 and that of more recent date 7#ahfc71 of ,borlinetto1 who developed the image in black with a silver nitrate alcoholic solution1 #a3ejj1 and after washing the picture in a solution of citric acid1 #a3aj1 fixed it by aqueous ammonia4 ,but1 although that is not absolutely necessary1 we would advise one working this1 or similar processes in which a silver salt is employed for developing1 to fix the image1 after treatment with citric acid to clear the proofs from iron salts1 in a solution of ammonium sulphocyanate--which has not the injurious effect of sodium thiosulphate 7hyposulphite7--in order to prevent the paper to be tinged by the reduction of the silver nitrate which is mechanically retained in its fiber4 ,the solution of ammonium sulphocyanate should be compounded with auric chloride to tone the picture at the same time it is fixed2 thus3 ,ammonium sulphocyanate #ce parts ,gold terchloride #j4ae part ,water #cej parts ,the solution can be used over again4 ,in the processes devised by ,dr4 ,phipson1 ,monckhoven and other authorities1 the double ammonio-ferric oxalate is rightly recommended instead of the simple oxalate4 ,not only is the preparation more sensitive to the luminous action1 but better half tones are obtained4 ,as usual1 it is advantageous to size the paper with starch4 ,the ammonio-ferric oxalate is prepared by precipitating ferric chloride or sulphate by aqueous ammonia1 then washing the precipitate collected on a filter until the washing water be neutral or does not evolve the smell of ammonia4 ,the precipitate is then placed in an evaporating dish1 and by small quantity is added a hot solution of ammonium oxalate until it is nearly 7not entirely7 dissolved1 when the solution is set aside for a few hours1 then filtered and evaporated to crystallization4 ,for use1 the crystals of ammonio-ferric oxalate are dissolved in the proportion of #a for #e of distilled water4 ,the solution as well as the crystals should be kept in the dark4 ,if one object to the trouble of crystallizing1 the solution can be prepared by dissolving the ferric oxide in a hot solution of #cj parts of ammonium oxalate and #be parts of oxalic acid in #ahj parts of water observing that the oxide must be in excess47#db7 ,the following sensitizing solution gives also excellent results3 ,ammonio-ferric oxalate #aj parts ,ammonio-ferric lactate #d parts ,water #ajj parts ,after exposure1 which varies from five to ten minutes1 according to the intensity of the light and the printing quality of the negatives1 the picture appears negative from formation of ferrous oxalate4 ,it may be developed in a great many ways3 by a solution of silver nitrate at #b or #c per cent4 of water acidified slightly by an organic acid--citric acid1 for example--or a diluted solution of ammonio-nitrate of silver1 which most likely constitutes the best developer2 the image is black and consists of metallic silver and ferric oxide1 with formation of silver oxalate1 which dissolve in the ammonia4 ,if the print be treated by a weak solution of aqueous ammonia1 the image turns green1 then brown1 and if1 before the latter coloration is obtained1 gallic acid or pyrogallol be added1 the image becomes bluish-black or brown-black4 ,in the same circumstances tannin 7gallo-tannin7 produces a blue-black image2 catechu-tannin7#dc7 and quino-tannin give green1 etc4 ,employed as a developer1 potassium ferricyanate develops an image in prussian blue1 and auric chloride one in the characteristic violet metallic gold4 ,to fix the images obtained by the latter reactions1 it suffices to wash them in a few changes of water1 and1 if developed with silver1 they can be toned by any of the alkaline solutions of auric chloride used in the printing out silver process1 etc4 ,the photographs obtained by all these processes are permanent4 ,,dr4 ,j4,b4 ,,obernetter',s ,,process 7#ahfc74 ,copper chloride #ajj parts ,ferric chloride1 sol4 sp4 #ac parts gr4 #a4e ,hydrochloric acid1 conc4 #ab parts ,c4 ,p4 ,water #a1jjj parts ,float the paper on this solution for about two minutes and hang it up to dry4 ,the keeping quality of the prepared paper is remarkable2 it has been kept for two years without apparent change2 its sensitiveness is at least one-third greater than that of silver albumen paper4 ,unless developed within an hour or two1 the vigor of the proof is much impaired2 after twenty-four hours a print can be taken over on the same4 ,when exposed1 only a faint image is visible4 ,it should be fixed in the following solution3 ,potassium sulphocyanate #ab parts ,sulphuric acid1 conc4 #a part ,sensitizing solution #aj to #ab parts ,water #a1jjj parts ,a print is floated on this solution1 face downward1 for three or four minutes1 taking care to agitate the liquid as little as possible2 the print is afterwards immersed and another one floated in its place1 thus proceeding until all the prints are immersed or the solution can hold no more4 ,a fresh solution is then added to strengthen it3 the older the solution the more rapidly and better it works4 ,in this developer copper cyanide is precipitated on the parts acted on by light1 and this exactly in the proportion to the luminous action4 ,the time of immersion depends on the method selected to finish the proofs2 it its from five minutes to half an hour4 ,if the proof is immersed for1 say1 twenty-four hours1 the image comes out in a relief which may bring the shadows to two lines in depth4 ,when well developed and thoroughly washed1 the proof can be dried and the subsequent operations made at any convenient time4 ,various processes may be employed to give to these proofs the tone required2 thus3 the prints well washed are placed in a solution of ferricyanate of potassium at #f to #ab per #ajj of water1 where they take a red color increasing in intensity4 ,if left over night the color becomes a splendid velvet deep red with perfect clear whites4 ,to obtain the color of silver photographs one hour's immersion is sufficient4 ,after this operation the proofs are washed until the water is no more tinged yellow4 ,by immersion in ,ferrous sulphate #ajj parts ,iron sesquichloride #dj parts ,hydrochloric acid #hj parts ,water #bjj to #cjj parts the proofs undergo the following gradation of colors3 red1 reddish violet1 blue-violet1 black and greenish black4 ,as soon as the desired color is obtained1 the proofs are washed in acidified water and dried4 ,the most beautiful purple violet is obtained by leaving the proofs in the iron solution until green-black1 and then washing for a moment in a dilute solution of sub-acetate of lead4 ,a brown-black may be produced by treatment1 after washing1 with an ammoniacal solution of hypermanganate of potash4 ,a weak solution of nitrate of silver also yields very fine pictures1 but the exposure should be very short1 and the proofs must be fixed in water containing a small quantity of oxalate of ammonia4 ,in order to impart to the proofs the gloss of silver photographs1 they should be albumenized in the ordinary manner1 and the albumen insolubilized by well known means4 ,the chemical actions in this process ,i explain in the following manner3 ,on the paper there are ,fe#b;,cl#c and ,cu,cl1 the latter in excess4 ,by the action of light1 and according to the transparency of the negative1 ,fe#b;,cl#c is reduced to ,fe,cl1 while ,cu,cl suffers no alteration4 ,if the paper be immediately placed in an absolutely dry room after exposure1 the picture remains unchanged4 ,in a moist atmosphere ,fe,cl attracts moisture and1 with a part of ,cu,cl1 is so decomposed that ,fe#b;,cl#c is formed together with ,cu#b;,cl4 ,after this action has commenced1 if the proof be not immediately immersed in a solution of sulphocyanate of potassium1 ,cu#b;,cl passes over to a higher combination of chlorine1 and the paper is again fit to be impressed anew by the action of light4 ,as long as ,fe,cl or even ,cu#b;,cl is present1 if the print is immersed in the sulphocyanate solution1 sulphocyanate of copper is immediately formed on the reduced parts1 while on the others the sulphocyanide of copper1 formed and dissolved by the sulphocyanide of potassium in excess1 becomes decom posed with water in soluble sulphocyanide of copper and deposited as such on the parts already covered with the salt4 ,frequently the prints appear yellow from formation of the double sulphocyanide of copper1 but the color disappears by washing in water4 ,red coloration is due to decomposition into ferrocyanide of copper4 ,l4 ,,liesegang',s ,,process 7#ahfe74 ,pour ammonia into a nitrate of uranium solution1 wash the precipitate of uranate of ammonia in distilled water1 then dissolve in citric acid4 ,mix this solution of citrate of uranium and a little of a solution of chloride of gold with a paste prepared by dissolving tapioca in hot water4 ,the quantity of chloride of gold must be small and the heat not too great1 otherwise the gold would be reduced4 ,spread the mixture with a sponge on the paper1 which takes a brilliant yellow color1 and expose when quite dry2 the proofs have the delicacy and vigor of albumen prints4 ,the proofs come from the frame with a bluish-black color2 they should not be toned1 but merely fixed by washing until the yellow color of the paper has disappeared4 ,the color of the picture can be changed to a purple by a solution of chloride of tin4 ,,guarbassi',s ,,process 7#ahfg74 ,the paper is floated in the dark for four or five minutes on a saturated solution of bichromate of potash4 ,when dry1 it is printed a little longer than for silver prints and afterwards floated1 face upwards1 on a water bath until all the unaltered bichromate is dissolved4 ,it is then immersed in the following solution1 which improve by use and tones the pictures to a reddish color3 ,saturated solution #d parts nitrate of mercury1 as free from acid as possible ,saturated solution #a part bichromate of potash ,distilled water #bh parts ,this solution should be prepared1 filtered and allowed to stand for some time before use4 ,the print is left in the bath until it has assumed an intense red color1 the whites remaining perfectly pure4 ,it is then washed and put in another bath to obtain a brownish tint4 ,this bath is thus composed3 ,conc4 aqueous ammonia #b parts ,distilled water #ajj parts ,the print must be immersed at once1 and when1 in a short time1 it has assumed the proper color1 it should be washed immediately4 ,the picture is toned in a very diluted solution of chloride of gold1 #a3g1jjj1 in which the color passes from a light brown to a deep black or a violet black tone1 when it is washed in two changes of water4 ,a4 ,,poitevin',s ,,process 7#ahgj74 8,i use a paper prepared with iron sesquioxide rendered sensitive to light by tartaric or1 better1 citric acid in concentrated solution4 ,this paper1 after desiccation and exposure to light1 possesses the property of reducing the solution of silver nitrate and that of chloride of gold1 and of turning blue with a solution of potassium ferncyanate in the parts where light has reduced the iron sesquichloride into the oxide at the minimum40 8,to coat the paper with an equal layer of iron sesqnioxide1 ,i brush it with a tuft of fine linen dipped in a solution of iron perchloride at #aj or #ab per cent4 of water1 and dry the sheets in the dark4 ,i immerse afterwards these sheets1 one after the other1 in a tray containing aqueous ammonia1 in such a manner as to well wet each sheet successively4 ,a sufficient number of sheets being immersed1 ,i pour off the ammonia in a vial1 and1 in the tray1 ,i wash them several times1 and remove them one by one to hang them up to dry1 even in full light1 the iron sesquioxide not being sensitive to light40 8,the paper can be prepared in quantities beforehand4 ,to use it ,i apply upon each sheet a solution of citric acid at #cj or #ce per cent4 of water7#dd7--which may be done by daylight--and let them dry in the dark40 8,exposed under a negative of the ordinary intensity1 the paper is impressed in sunshine in a few minutes2 in the shade it requires about the same time as chloride of silver paper40 8,after exposure the image is not visible1 and without being obliged to shelter it from light1 ,i immerse the print in a solution containing about #a per cent4 of silver nitrate4 ,this solution can be used over and over again1 by adding to it a little of the silver salt4 ,it does not become turpid by use2 it simply turns slightly green from formation of iron nitrate4 ,the image appears soon and rapidly becomes vigorous2 in half an hour it will be completely developed4 ,when the exposure is sufficient the color is deep sepia1 but not so intense if the quantity of citric acid is feeble4 ,no fixing is necessary2 it suffices to wash in several changes of waters40 8,the image can be toned with great facility by a weak solution of gold or of platinum chloride1 or1 better1 by a mixture of these two salts4 ,if the impressed paper be treated by a very diluted solution of potassium ferrocyanate1 one obtains very pretty blue proofs40 8,a weak solution of gold chloride develops a violet image4 ,a solution of platinum chloride has no effect40 8,all the various phases of this printing method can be followed in full 7diffused7 light2 there is only the desiccation of the paper when sensitized with citric acid1 which requires to be done in the dark40