,,the ,,glue ,,book ,illustration3 ,,modern ,,glue-,,testing ,,laboratory 7,courtesy of ,a4 ,t4 ,deinzer1 ,monroe1 ,mich47 ,,the ,,glue ,,book ,,how ,,to ,,select ,,prepare ,,and ,,use ,,glue ,a ,,short1 ,,practical ,,discussion ,,of ,,matters ,,important ,,to ,,every ,,glue ,,user ,j4 ,a4 ,,taggart1 ,,toledo1 ,o4 ,,copyright #aiac1 ,j4 ,a4 ,,taggart ,,author',s ,,note ,the purpose of this manual is to provide a practical guide for glue users1 to help in eliminating waste and improving the quality of product4 ,that there is an enormous waste due to improper preparation and use of glue is well known to all who are in touch with the subject4 ,some authorities estimate that #gj of the glue used in the ,united ,states is improperly handled4 ,the actual waste is said to be in excess of #be of the amount of glue used2 to say nothing of the loss due to imperfect condition of the completed work4 ,the writer knows from actual experience that many glue users are ignorant of the proper methods to be employed2 and that many others are careless1 or indifferent4 ,the handling of glue is a subject on which much new light has been shed in recent years4 ,there is no longer any reason why the glue user should not know the correct methods to follow4 ,this treatise is intended as a handbook for the glue user who is interested in increasing the efficiency of his operations4 ,technical expressions have been avoided1 the whole matter being set forth as much as possible in the everyday terms in familiar use in the glue-room4 ,so far as the author can learn1 from an extended investigation1 no book has been published on this subject exactly answering the needs of the average glue user4 ,several excellent works are available which would be interesting to a man technically trained in the subject2 but although they embody many helpful suggestions1 they are not in such form as to be of the greatest value to the practical man4 ,no pretense is made for the present manual of disclosing new facts2 but rather of assembling in handy and easy reference form a summary of the best modern practice which the glue user of today may rely upon as a safe and convenient guide4 ,,table ,,of ,,contents ,,chapter ,i ,,importance ,,of ,,the ,,industry ,glue industry founded in ,america by ,peter ,cooper--increase in capital invested--increase in production--variety of uses--increase in requirements ,page #ae ,,chapter ,,ii ,,the ,,manufacture ,,of ,,glue ,sources from which glue is made--boiling the stock--drying--preparation in commercial form ,page #ag ,,chapter ,,iii ,,testing ,,and ,,grading ,,glue ,grades established by ,peter ,cooper--the tests--viscosity or fluidity test--the jelly test--apparatus for making jelly test--the finger test--a simple1 practical test for glue users--sampling--bubbles--surface indications--color indications--alkaline or acid quality--breaking quality--foam--grease--keeping properties--odor--laboratory test ,page #be ,,chapter ,,iv ,,correct ,,methods ,,in ,,the ,,glue-,,room ,much waste through faulty methods--importance of correct practice--soak glue in cold water before melting--test glue by water absorption--appliance for water absorption test--melting or dissolving glue--do not heat higher than #aej ,f4--apply heat indirectly--live steam ruins glue--use thermometer--heat glue slowly--cleaning the melting pot--importance of using copper1 brass or aluminum utensils--guard against evaporation--melt only the amount required--importance of cleanliness--keeping the glue-room warm--use by weight--storing--applying glue--securing workers' co-operation ,page #dc ,,chapter ,v ,,modern ,,glue-,,room ,,equipment ,modern appliances now available for all users--only copper1 brass or aluminum should come in contact with glue--the scientific glue-heater--the automatic temperature controller--keep steam away from glue--glue spreaders--clamps and presses--distributing glue in large plants ,page #fe ,,chapter ,,vi ,,which ,,glue ,,to ,,use ,accurate records important--the best glue for wood joints--veneers--sizing--paper boxes--belting and other leather goods--bookbinding--emery purposes--how much to pay--waterproof glue--vegetable glue--quick-setting glue--flexible glue ,page #gi ,,the ,,glue ,,book ,,chapter ,i ,,importance ,,of ,,the ,,industry ,glue is now so extensively used1 and for so many different purposes1 that it certainly deserves much more intelligent treatment at the hands of users than it has received heretofore4 ,since #ahcg1 in which year ,peter ,cooper1 who may justly be regarded as the founder of the glue-making industry in the ,united ,states1 produced the first ,american-made glue1 the yearly output has steadily increased4 ,by #ahhj1 the amount of capital invested in the making of glue had reached #d1jjj1jjj4 ,in #aije1 it was #aj1jjj1jjj1 and is now between #ab1jjj1jjj and #ac1jjj1jjj4 ,the annual production has increased in about the same ratio4 ,in #ahhj1 it was #d1jjj1jjj2 at present it is about #ae1jjj1jjj4 ,glue is an important by-product of the great packing houses4 ,those in touch with the industry know how extensively glue enters into the manufacture of articles of everyday use4 ,the general public hardly realizes that glue is used not only in making wood-joints and veneers1 but in the production of paper1 of silks1 hats1 carpets1 rugs1 and hundreds of other necessities4 ,america now produces glue of excellent quality to meet practically all requirements4 ,so great are the requirements that almost the entire amount of the ,american-made glue is absorbed by the home demand4 ,,chapter ,,ii ,,the ,,manufacture ,,of ,,glue ,an understanding of the sources from which glue is derived and of the processes of manufacture will be found of practical importance to the glue user4 ,it will give many valuable side-lights on the proper methods of preparation and handling4 ,glue is an organic substance of adhesive properties obtained from the hides1 skins1 bones and sinews of cattle1 sheep1 deer1 horses1 and other animals4 ,tails1 snouts1 ears1 and the pith of the horn are also used4 ,some glue is produced from the heads1 bones and sinews of fish4 ,the tendons and intestines of many animals1 the swimming bladder of many varieties of fish2 rabbit skins1 or 8coney10 from which the fur has been removed2 old waste leather1 such as gloves1 butchers' offal1 or 8country bone20 8junk0 bones1 and much other apparently worthless matter1 all contribute to the raw material of the glue-maker4 ,in its broadest sense glue may be understood to include gelatine1 but the use of the word is here confined to the substance known commercially as glue1 and which in contrast with gelatine has greater adhesiveness1 stiffness1 and elasticity1 and is also darker in color and more nearly opaque4 ,neither gelatine nor glue exists already formed in nature2 they are both the products of the action of heat and water on nitrogenous animal tissue4 ,it is not definitely known just how this change takes place4 ,some writers regard glue as impure gelatine2 others believe that there is a difference in nature between gelatine and glue4 ,this question is without present importance for our purpose4 ,,boiling ,,the ,,stock ,glue is produced by boiling the animal substances mentioned above1 and drying the resulting liquor4 ,the following may be noted in connection with the use of skins4 ,the outer covering1 in which the wool1 fur or hair is rooted1 is of no importance to the glue-maker4 ,the portion that produces the glue lies next to it1 being composed of fibres which run in every direction and contain the fluid matter which aids in keeping the skin moist and pliable4 ,the fat cells are directly beneath the glue-yielding portion1 and as fat is undesirable1 because it makes the glue greasy1 the shreds of fat are saponified by being subjected to a lime bath4 ,the lime bath is also useful in removing any hair still adhering2 and is used also in preparing tissue1 to remove bloody and fleshy particles4 ,this part of the process may consume from one to three days4 ,it may be noted in passing that the older the animal1 the more solid the glue will be4 ,on this account many manufacturers sort the skins before using4 ,being animal stock1 the raw material of glue is subject to decomposition1 and the scraps of hide are therefore carefully preserved1 especially during the summer season4 ,the tanneries supply most of the hide stock1 but only waste pieces reach the glue manufacturer1 as leather is more valuable than glue1 and the larger portion is therefore reserved for the tanner's use4 ,various names are used to describe the parts of hide that the tanner discards for the glue-maker's use--the heavy trimmings are 8pieces20 the hide pared off the hair or grain side1 8skivings20 the parts scraped from the flesh side are 8fleshings40 ,at the packing houses the heads1 feet1 ribs1 and other bony structures go direct to the glue-room4 ,if bone is sweet and fresh it is known as 8green10 or 8packer0 bone4 ,the waste of button and knife factories is also used4 ,bones are usually ground1 and they are treated with a sulphuric acid bath to attack and separate the lime and gelatine of which the bone is composed4 ,bones1 after being treated in this way1 become pliable and soft1 and the sulphuric acid is then removed by centrifugal force4 ,the acid must all be removed1 as the glue will granulate if any remains4 ,other parts of the stock are always carefully washed before boiling4 ,after the stock has been prepared1 it is placed in a boiler with false bottom provided with an opening through which the liquid may be run off4 ,the boiling of the stock is an operation that must be carefully conducted1 as the application of a greater degree of heat1 or for a longer time than is necessary1 damages the glue4 ,the boiler is heated by direct firing4 ,as the boiling proceeds1 test quantities of the liquid are run off for examination1 and when a sample is found on cooling to form a stiff jelly1 it is ready to draw off4 ,the first boiling usually occupies about eight hours4 ,when the liquid has been run off from this boiling1 more water is added and the boiling is continued4 ,this operation is repeated until the stock has yielded all of its gelatinous matter4 ,as many as six or eight boilings may be made4 ,the liquid first run off--the 8first boiling0--is always best1 as the effect of repeated or prolonged application of heat is to weaken the glue tissue4 ,the later boilings are also as a rule darker in color than the earlier ones4 ,,drying ,the glue-solution from the boiling process is run into wooden troughs or 8coolers10 about #f feet long1 #b feet broad1 and a foot deep1 in which the solution sets in a firm jelly4 ,when set1 a little water is run over the surface1 the jelly is detached from the cooler1 cut into uniform slices of the thickness desired1 and placed on galvanized or linen nets to dry4 ,drying may be done in the open air if weather conditions are favorable1 or in a drying-room4 ,the latter method is preferable4 ,conditions can be regulated to insure uniform drying4 ,piles of the nets1 or 8stacks10 are loaded on trucks and taken into the drying-room1 where they are exposed to the effect of warm air currents induced by blower or pressure fans1 or exhaust or suction fans4 ,the drying is a source of concern to the manufacturer4 ,it is extremely important to keep the temperature at just the right point1 to protect the glue from dust and dirt1 and to avoid the possibility of bacterial growth in the glue-jelly1 which is very susceptible to the development of harmful organisms4 ,the final form of the glue will be in sheets1 strips or flakes1 or ground4 ,for commercial purposes it is put up in packages1 bags and barrels4 ,,chapter ,,iii ,,testing ,,and ,,grading ,,glue ,there is as yet no uniformity of opinion among glue manufacturers and glue users as to how glue should be tested and graded4 ,in a general way the manufacturer knows what kind of glue a certain stock will produce2 but on account of variations that are sure to occur1 it is necessary to subject each glue to certain tests1 according to standards more or less definitely established4 ,the grades in general use are those originally employed by ,peter ,cooper1 and are as follows3 ,a ,,extra ,no4 #a #a x #a1 #a1 #a1 #a1 #a1 #a ,the only way to determine which is the best glue to use1 is by trying out various grades in actual practice4 ,the best glues for ordinary uses are well understood 7see pages #gi to #he for suggestions on this subject74 ,between two or more glues of any one type1 actual experiment is the only safe guide4 ,most glue men will give you good advice2 but above all1 keep accurate records of results of the different grades used4 ,when you have found the right glue1 keep to it4 ,,the ,,tests ,glue is graded on physical characteristics rather than on chemical composition4 ,various chemical tests have been proposed1 but they are unimportant so far as practical working value is concerned4 ,the most important physical tests are those for viscosity1 and jelly strength4 ,,viscosity ,,or ,,fluidity ,,test ,the test for viscosity1 or fluidity1 is based on the idea that the greater the tenacity of the glue1 the greater will be its cohesiveness1 and the less will be its flowing power4 ,in other words1 the higher will be its viscosity4 ,in testing for viscosity1 water is used as a standard4 ,a solution is made of the glue1 and the rate of flow of the solution at a certain temperature is compared with the rate of flow of water under the same conditions4 ,several devices are on the market under the name of 8viscosimeter0 for measuring the viscosity of glue4 ,while they vary in detail they are in principle a pipette from which the glue-solution flows at a given temperature4 ,the time required for the glue to run out of the pipette as compared with the time consumed in the same operation by the same quantity of water gives the relative viscosity of the glue4 ,the viscosity test is not entirely accurate in itself1 but taken in connection with the jelly test it forms a very satisfactory basis for grading4 ,,the ,,jelly ,,test ,the jelly test is based on the comparative resistance power of the various glue-jellies4 ,several mechanical devices for determining jelly-strength have been perfected4 ,one of these consists of a brass vessel which rests upon the glue-jelly1 and into which shot is poured2 the weight of the cup and the contained shot upon having penetrated to a certain depth in the glue-jelly1 gives a figure which expresses the comparative strength of the jelly with the standard4 ,,apparatus ,,for ,,making ,,jelly ,,test ,illustration3 ,apparatus for ,testing ,jelly-,strength of ,glue4 ,another apparatus that has been found accurate and practical is the device illustrated on the next page4 ,it consists of a pressure tube 7,a71 over the mouth of which is stretched a thin rubber diaphragm 7,b74 ,the tube connects to a rubber bulb 7,m7 and to a pressure gauge1 or manometer 7,e7 with a scale 7,f74 ,the pressure tube is filled with water to the point 7,c74 ,the manometer tubes also contain water4 ,a three-way stop-cock 7,d7 connects the tubes either to the bulb 7,m71 or to the air1 depending on the position4 ,below the pressure tube is a brass table 7,g71 on which is placed the glass containing the glue-jelly to be tested4 ,when the glass is in position1 the table is raised by means of a threaded wheel until the glue surface forces the water resting on the flexible diaphragm up to the fixed mark ,l4 ,then the stop-cock is turned to connect the pressure tube and gauge to the rubber bulb4 ,by pressing the bulb the water is forced down in the pressure tube and so expands the diaphragm into the jelly1 the liquid in the gauge rising simultaneously4 ,pressure on the bulb is continued until the water reaches the mark ,n4 ,thereupon the stop-cock is again turned1 the water is held at the point ,n1 and the pressure is indicated by the height of the liquid in the gauge4 ,the degree of pressure is the measure of the consistency of the glue-jelly4 ,the initial contact between the jelly and the rubber diaphragm is always the same1 all jellies therefore having the same initial pressure4 ,when the diaphragm is forced down into the jelly1 the pressure required depends entirely upon the resistance that the jelly offers4 ,the slightest difference in the consistencies of the various jellies will alter the pressure required1 the differences being accurately recorded by the gauge upon the scale4 ,advantages of this apparatus are that the relative value of the jelly compared with the standard is expressed in concrete figures2 the method of operation is simple2 and the instrument is so sensitive that it will record a change in reading between two samples of glue in which a difference of #a_/ajjth ounce of dry glue is used4 ,repeated tests may be made on the same jelly1 as the surface is not broken4 ,with a little practice a single glue may be tested in twenty seconds1 or less4 ,,the ,,finger ,,test ,one of the most satisfactory methods of determining jelly-strength--and the one perhaps in most general use1 is the finger test4 ,in this test the various glue-jellies are arranged before the tester1 who presses each with the tip of the finger1 comparing it with the standard as to resistance power4 ,while this may seem to expose the final decision too greatly to the personal equation1 as represented by the personality of the glue-tester1 it is nevertheless true that an expert develops the most extraordinary precision1 arriving at conclusions that are corroborated by the results of other tests and by the results in actual practice4 ,the work of the glue-tester is analogous to that of the coffee-taster and the tea-taster1 or experts in other lines1 who through a highly developed and keenly discriminating sense of taste1 or touch1 or smell1 determine with extreme nicety the physical characteristics of the substances that they are accustomed to test4 ,,some ,,simple1 ,,practical ,,tests ,,for ,,glue ,,users ,to perform the tests described requires a degree of experience and an equipment beyond the reach of the ordinary buyer and user of glue4 ,certain tests may however be made that are of great value in determining important facts about the glue it is intended to buy and use4 ,these tests could not be used as a basis for grading glue scientifically1 but they are exceedingly valuable in determining its purity and its adaptability to the work in hand4 ,,sampling ,in the first place you should carefully sample your glue with a view to testing4 ,take several samples from various parts of the barrel4 ,flake glue is often made up of different varieties1 and a single sample may not be at all representative4 ,ground glue1 from its very nature1 is easily adulterated4 ,it should be examined in a good light1 for evidence of foreign substances4 ,examine flake glue carefully also for uniformity of odor and general appearance4 ,if glue has been adulterated while in original form it is practically impossible to determine the adulteration by external appearance4 ,subsequent adulteration may be detected4 ,,bubbles ,if you should notice white bubbles1 in the shape of round blots1 on the surface of the glue1 you have found evidence of decay4 ,if there is any doubt in your mind you can complete the evidence by moistening the glue4 ,if it gives off a sour odor you have an additional indication of putrefaction4 ,such glue should be avoided4 ,bubbles may appear within the glue--not on the surface--without being an indication of putrefaction4 ,as a matter of fact1 bubbles are practically always found in certain high-grade glues1 though practically never in low-grade bone or hide glues4 ,they are supposed to be due to the air which gets in when the glue is poured into the moulds4 ,when glue is originally dried on nets in very cool and dry weather1 such bubbles are frequently found4 ,always beware of glue showing surface bubbles4 ,,surface ,,indications ,besides being free from bubbles or blots a good glue is smooth1 though not necessarily glossy4 ,sometimes the very best glue will be of a dull color1 and many inferior glues even have a very shiny surface4 ,the surface should be uniform in color and in appearance4 ,,color ,,indications ,these are not important1 as a rule4 ,the color of any particular lot of glue should be nearly uniform2 otherwise it is subject to the suspicion of adulteration4 ,bone glues are usually darker than hide glues1 but some bone glues go through an artificial clarifying process which gives them the appearance of high-grade glues but really detracts from their strength4 ,very frequently oxide of zinc is added to glue1 the effect being to make it set quickly1 as well as to give it a light color4 ,some glues contain so much oxide of zinc that they are milk-white4 ,zinc oxide is not harmful except when added in very large quantities4 ,,alkaline ,,or ,,acid ,,quality ,the best glues are neutral as to acid and alkali4 ,glues with an excess of acid should be avoided1 especially when used with oak or chestnut or other woods with strong acid qualities1 as the acids in the glue may unite with those in the wood in such way as to have a destructive effect upon the glue4 ,in such cases the glue will granulate after a time and the work will pull apart4 ,when a wood is being used that is strong in acid it is advisable to use a glue containing enough oxide of zinc to neutralize the acid in the wood4 ,in making sizing for paper a glue containing either acid or alkali in excess should be avoided4 ,it is also held by some authorities that acid in glue tends to bring about decay4 ,to test for alkali or acid1 dissolve a small quantity of glue in water and dip a piece of litmus paper into the solution4 ,acid will turn the paper violet or red4 ,alkali will turn it blue4 ,litmus paper may be procured at any drug store4 ,,breaking ,,quality ,this is a simple test that affords an important indication of the quality of glue4 ,take a small piece between the thumb and forefinger of each hand and bend it4 ,a very thin piece of good glue will bend without breaking4 ,when it does break1 if the edges are splintery1 great tensile strength is indicated4 ,a clean fracture1 on the other hand1 indicates a brittle1 low-grade glue1 which has been subjected to heat so long as to destroy the tissue2 or else it has been made from bone stock4 ,high-grade glues never show glassy fractures1 but bone glues do4 ,in making this test1 the air conditions of the room should be taken into account4 ,if the glue has been kept in a dry room it will naturally break much more readily than if it has been in a moist atmosphere4 ,this is especially important to bear in mind if comparative tests are being made4 ,,foam ,a simple test for foam is to beat a solution of glue with an ordinary eggbeater4 ,glue which shows foam1 or in which foam does not quickly subside1 probably contains impurities4 ,foam is especially frequent in alum-dried glues and in cheap bone glues4 ,some authorities believe that foam is caused by overheating1 due to scalding by contact with steam jacket1 or by steam coming into direct contact with the glue1 or by heating for too long a time1 or it may be due to the fact that all the grease has not been eradicated4 ,glue that foams at ordinary temperature should be avoided for good work4 ,,grease ,a moderate amount of grease may be a good thing when using with clay or with colors1 but a large proportion of grease should be avoided when making glazed or coated papers1 or in general use4 ,a glue at ordinary temperature which is not overheated on which a scum rises has an excessive amount of grease4 ,it shows that the glue has not been properly skimmed in manufacture4 ,,keeping ,,properties ,the keeping property of glue may be determined by letting the glue-jelly stand for several days exposed to the air1 and noting any deterioration4 ,it is customary to let the jelly stand at room temperature--but if the glue is to be kept under any special conditions the test should be made as nearly under these conditions as possible4 ,,odor ,deterioration is always accompanied by a sour odor4 ,avoid using any glue that does not smell clean and sweet4 ,,laboratory ,,tests ,up-to-date practice in all the larger concerns using glue demands a laboratory for making tests4 ,an expert is put in charge and the glue analyzed chemically as well as for its physical properties4 ,this method cuts the guess-work down to a minimum4 ,manufacturers whose output would not permit the employment of an expert all the year round can have glue analyzed in laboratories maintained for such purposes4 ,it means often a great saving of money in the end to learn the exact properties of the glue you propose to use1 or that you may be actually using4 ,we may also repeat what we have already said about securing competent advice from manufacturers4 ,the glue user who takes a responsible manufacturer or glue house into his confidence will secure valuable counsel4 ,it is to the glue-maker's and glue salesman's interest to have you secure good results4 ,they have a large experience to draw on1 and when checked up by the results from actual practice in your glue-room their advice in regard to the selection of glues is usually worth heeding4 ,,chapter ,,iv ,,correct ,,methods ,,in ,,glue-,,room ,it is quite certain that glue-room methods in many factories are years behind the times4 ,this is due to poor equipment1 to ignorance and to carelessness4 ,many factories could not continue in business if the hit-and-miss methods of the glue-room prevailed in other departments4 ,it is possible to spoil the very best glue by improper methods of preparation2 and not only is a vast amount of glue rendered totally unfit for satisfactory work1 but a great deal is wasted2 the total loss1 through faulty methods1 being about #be of the entire amount used4 ,there is no reason why there should be such loss in the glue-room4 ,the proper methods of procedure have been definitely established4 ,putting them into effect not only saves glue1 but it enables better work2 saves time of workmen1 and increases greatly the general efficiency of glue-room operations4 ,the following rules are a guide to correct practice4 ,,always ,,soak ,,glue ,,in ,,cold ,,water ,,before ,,melting ,the function of soaking is to get back into the glue the liquid it originally contained4 ,soaking in cold water gets the glue into proper condition to dissolve readily when heat is applied4 ,if glue is soaked in warm water1 or if melted without soaking1 the glue on the outside will dissolve at once1 and this will coat the remainder with a film1 so that it will not readily dissolve1 except when heat is applied in a degree that is harmful4 ,glue has an affinity for cold water4 ,good glue will absorb from #a times to #b times its weight of cold water4 ,if glue is in flakes or strips1 break up into small pieces4 ,soak the pieces from #aj to #ab hours in cold water4 ,soak ground glue #a to #d hours in cold water4 ,naturally the thinner the glue the less time required for thorough soaking4 ,the glue should be soaked through thoroughly and not merely moistened on the outside4 ,you can determine whether the soaking has been completed by breaking a piece in two and noting conditions at the centre4 ,if pieces are permitted to stick out beyond the level of the water1 the natural result is that such pieces will be only partially softened4 ,as the melting proceeds1 these will slip to the bottom of the kettle1 and in order to melt them long heating and high temperature are required4 ,this means damaging the strength and adhesiveness of the glue4 ,in soaking ground glue it is a good plan to keep stirring as the glue is added to the water in the soaking vessel1 as this helps to keep the fine particles of glue immersed in the water1 instead of floating on the top4 ,this is true also of thin-cut1 high test glues4 ,,use ,,only ,,pure1 ,,cold ,,water ,in soaking and thinning glue1 use only pure1 cold water4 ,unless heater is provided with pure water attachment or pure water chamber1 avoid using water from the glue-heater4 ,do not use water from boilers1 for such water contains pipe-rust1 acids from boiler compounds1 sediment1 and other matter extremely harmful to glue4 ,see to it that all soaking vessels are scrupulously clean4 ,,testing ,,glue ,,by ,,water ,,absorption ,the soaking of glue in cold water before using is employed in some factories as a basis for comparative test of working quality4 ,the amount of water absorbed may vary as much as #aj ounces in half a pound4 ,other things being equal1 the glue that absorbs the most water is of course the cheapest to use4 ,as a comparative test1 melt up say #aj pounds of glue and see how much work it will do compared with the glue you are now using4 ,a ,,simple ,,glue-,,tester ,,for ,,determining ,,water ,,absorption ,a simple and accurate apparatus may be had for determining the amount of water the glue will absorb for best working results1 and also whether the amount of water actually used is the proper amount for this particular glue4 ,it is important to know these facts1 since the more water a glue will absorb under proper working conditions1 the cheaper that glue is to use4 ,the apparatus in question is illustrated on the next page4 ,it consists of a copper pot and a hydrometer arranged for a temperature of #ge ,c41 or #afg ,f4 ,a sample of the glue to be tested is poured into the pot and the hydrometer is slowly allowed to sink into the solution until it finds its correct position4 ,if the glue-solution is1 for instance1 #a part glue to #c parts water1 the hydrometer will drop to #be on the hydrometer scale4 ,this will show that you have #be dry glue in the solution4 ,the hydrometer is fitted with a temperature correction scale that enables the readings to be adjusted to the temperature of the glue-solution4 ,illustration3 ,apparatus for ,testing ,glue in ,solution ,by noting the working qualities of glue prepared with various proportions of water1 you can determine what is the correct amount of water to use1 and then by using the hydrometer as each batch is prepared1 you can be sure that the correct proportions are always being used4 ,by making readings from time to time with the hydrometer1 you can also determine the amount of evaporation that is going on1 and in this way guard against the glue becoming too thick for proper use4 ,no special skill is required to use the hydrometer1 and the readings are so quickly made1 that tests can be made in every department in which glue is used without loss of time4 ,,melting1 ,,or ,,dissolving1 ,,glue ,after the glue has been soaked in the manner described1 the most important part of the process is undertaken--that is1 the melting of the glue by application of heat4 ,the words 8most important0 are used advisedly4 ,it is safe to say that most of the damage done to glue occurs in the melting process4 ,there are all kinds of ways of melting glue1 but many of them absolutely ruin glue for practical work4 ,as this is a very important subject1 it is well to get the rudiments thoroughly in mind--and for this purpose the reader should remember what has been said about the nature of glue--that it is made from animal matter2 and that it is composed of innumerable small fibres on whose strength the holding power of the glue depends4 ,whatever injures and breaks down these fibres inevitably weakens the glue2 so that in melting1 every care must be observed to avoid the breaking down of the glue-fibres4 ,the most common destructive agent is heat4 ,just as the application of heat breaks down the fibres of a roast of beef1 rendering it 8tender0 as the saying is1 so the prolonged application of heat1 or heat of too great an intensity1 will destroy the glue-fibres1 and therefore radically impair their value for actual use4 ,so1 it is absolutely necessary to employ no more heat in melting glue than is required to reduce the soaked mass to the proper working consistency4 ,,do ,,not ,,heat ,,glue ,,higher ,,than #aej ,f4 ,by actual experience it has been determined that a temperature of #acj to #aej ,f4 is all that is required to melt the glue to the requisite consistency2 any greater heat is actually harmful1 as it assists just so much more in the process of disintegration4 ,the term 8boiling10 or 8cooking10 never should be applied to the process of glue melting4 ,these words imply a temperature of #bab ,f4--and such a temperature is ruinous to glue4 ,in producing glue from the original stock--from the hides1 bones1 sinews1 etc41--boiling is necessary1 in order to extract the gelatinous matter--but as we have already seen1 the longer the stock is boiled1 the weaker the product4 8,first boilings0 are always best4 ,in preparing for use1 however1 boiling is not necessary2 therefore1 never heat glue above #aej ,f4 ,,apply ,,heat ,,indirectly ,heat never should be applied directly1 as this results in burning1 or scalding1 the glue4 ,some glue-melting appliances have been constructed in which steam is turned directly upon the glue mass4 ,this is bad practice of the most harmful kind4 ,steam never should come into direct contact with glue4 ,the temperature of steam is always at least #bab ,f4--under pressure it is much higher--and consequently it cooks the glue and destroys the fibres4 ,live steam burns glue just as it burns your hand if turned directly upon it4 ,the destructive effect of live steam upon glue may not be noticed at once1 but work on which overheated glue has been used will eventually pull apart on account of the destruction of the glue-fibres4 ,,live ,,steam ,,ruins ,,glue ,one of the largest glue manufacturers in the country makes the following comment on this subject3 8,in regard to the effect of live steam turned into a pot of glue1 whether flake1 ground1 or jelly--the glue would become overheated1 and you know that always has a disastrous effect4 ,the temperature of live steam is #bab1 and under pressure it is even higher1 so that at least the glue around the pipe will attain a temperature of #bab4 ,the effect will be that the glue will be cooked to death and lose its strength4 ,we would certainly discourage the application of live steam for dissolving glue as there is nothing to gain by it and everything to lose40 ,opinions of other manufacturers are unanimous on this point4 8,we know of factories where they have made a careful test10 writes one1 8and the results obtained from glue where it was melted with a live steam jet and where it was dissolved in a jacketed kettle were so greatly in favor of the latter method that it is used universally today40 ,a further vital objection to the use of steam direct is that the steam contains acids from boiler compounds1 dirt1 pipe-rust and sediment1 all of them injurious to the strength and to the elasticity of glue4 ,then too1 glue always takes up moisture from steam4 ,this changes the consistency of the glue4 ,it leads to guess-work4 ,the quantity of water added to glue must always be exactly regulated4 ,turning live steam on glue prevents proportions of glue and water remaining constant4 ,,use ,a ,,thermometer ,the only safe procedure in melting glue is to use a thermometer4 ,if glue is melted in an open pot1 or one in which the contents of the glue chamber can be reached easily1 an ordinary drop thermometer1 encased in a frame for protection1 may be used4 ,it is preferable1 however1 to have the thermometer a part of the apparatus1 with the mercury tube extending into the glue chamber4 ,in this way it is easy to keep watch on the temperature of the glue mass at all times4 ,an improvement even on this method is found in the automatic temperature controller that may be had with some glue-melting appliances1 by which the supply of heat is automatically regulated4 ,when the temperature in the glue chamber passes #aej ,f4--the absolute maximum of safe temperature--the valve automatically closes and shuts off the heat1 re-opening again when the temperature has lowered from #e to #aj4 ,by the use of the automatic temperature controller the temperature is kept at the proper point1 and there is no necessity of making observations with the thermometer except to verify your controller4 ,the temperature controller not only permits the scientifically correct preparation of glue1 preventing overheating and ruined work1 but saves also in expense of supervision4 ,,heat ,,glue ,,slowly ,glue should be heated slowly1 requiring about #cj minutes4 ,rapid heating dissolves the outer portions of the glue quickly1 and a scum is then formed over the rest of the glue1 preventing its proper melting4 ,the following precautions will be found useful to put into practice4 ,,cleaning ,,the ,,melting ,,pot ,dirt enters the melting-pot through the glue itself1 the introduction of dirty brushes1 or the exposure of the pot to dust1 etc4 ,if glue is melted in a dirty pot1 the skin forming on the surface of the glue liquor gradually accumulates at the sides of the kettle and slowly decomposes4 ,this may or may not fall into subsequent melts1 thus contaminating them4 ,the only way to make sure that it will not do so is to clean the pot4 ,much unnecessary waste of glue may be avoided through observance of the following procedure4 ,the contents of the melting-pot exhausted1 scraps of dried glue1 as well as scraps of partially dried jelly adhering to the sides should be detached mechanically1 as thoroughly as possible1 and examined4 ,if clean1 they may be replaced in the bottom of the kettle2 if dirty1 they are to be set aside temporarily4 ,in the first instance1 they are covered with the minimum of water necessary to soften1 and the sides of the kettle swabbed with a little water in order to soften any glue that has dried and has not been detached mechanically4 ,the pot is then gently heated in order to bring the scraps into solution1 this solution used in work1 and the pot thoroughly washed out with hot water and cooled before soaking a fresh portion of glue4 ,if the scraps have proved dirty1 but not sour1 they may be kept warm enough to permit the dirt to settle1 when the glue may be used without risk4 ,if sour they must be thrown away4 ,if the glue-pot is properly cleaned there is no danger of souring and all the glue may be used without waste4 ,it may be contended that much labor may be saved by adding sufficient water for the next melt1 and through this means soften all glue adhering to the kettle in connection with that added fresh4 ,it will be found1 however1 that the freshly added glue will absorb the bulk if not all of the water1 leaving adhering scraps practically unsoftened1 which in this way continue to accumulate1 interfering with the proper working of the glue4 ,pots1 kettles1 brushes1 everything that comes into contact with glue1 should be regularly and rigidly inspected1 and kept absolutely free from dust and dirt4 ,this is extremely important4 ,,use ,,copper ,,and ,,brass ,,or ,,aluminum ,,utensils ,an important aid to cleanliness is the use of copper1 aluminum or brass for all parts of the apparatus with which glue comes into contact4 ,not only are copper1 aluminum and brass the cheapest materials to use in the long run1 due to their resisting acids in glue1 water and steam which quickly corrode iron1 but copper1 aluminum and brass are practically self-cleaning4 ,iron equipment is especially bad4 ,it is most expensive in the end1 for iron is quickly eaten away by acids in glue and water4 ,iron rusts1 and the rust impairs the color and quality of the glue liquid4 ,do not use iron vessels under any conditions4 ,,guard ,,against ,,evaporation ,a great deal of waste in the use of glue is due to evaporation4 ,if glue is heated in open pots1 evaporation is very great4 ,evaporation weakens glue2 makes it too thick for use1 and also makes it very uneven in quality4 ,glue should always be melted in a closed vessel4 ,,do ,,not ,,melt ,,too ,,much ,,at ,,one ,,time ,as glue deteriorates quickly if allowed to stand1 no more should be prepared than is needed for a single day's work4 ,it is even better to prepare it twice or oftener during the day4 ,if glue is dissolved at the proper temperature and kept at that same temperature after melting1 no noticeable deterioration results during the course of the working day4 ,but if allowed to stand over night its value decreases1 and it should not be mixed with fresh glue1 as it is not of the same consistency4 ,with practice and observation you can easily determine each day's needs in advance and prepare each morning just the right amount4 ,,cleanliness ,,of ,,first ,,importance ,glue is extremely sensitive to impurities4 ,cultures of germs are grown by bacteriologists in gelatine glue because they afford an ideal breeding place for germs4 ,glue quickly absorbs odors1 and decays rapidly if exposed to impurities4 ,decayed or decaying glue is not only extremely unpleasant to handle1 but it is worthless to work with4 ,keep your glue clean4 ,keep it away from strong odors4 ,glue will keep sweet and clean before melting just as long as you care to keep it so4 ,,keep ,,glue-,,room ,,warm ,,and ,,free ,,from ,,drafts ,glue can not be expected to do good work if not kept at uniform temperature4 ,see that the glue-room is of a temperature that facilitates uniform consistency of glue4 ,avoid possibility of drafts and consequent chilling of the melted glue4 ,do not let glue freeze4 ,if glue-jelly is frozen through it will crumble and act about like overheated glue4 ,glue frozen only around the edges does not show pronounced deterioration4 ,do not take any chances4 ,keep the glue-room temperature above freezing at all times4 ,,use ,,by ,,weight ,glue is sold by the pound and should be used by the pound4 ,weigh not only the glue1 but weigh the water as well4 ,keep an accurate record of weights4 ,,storing ,glue should be stored in a dry place4 ,barrels should not be unheaded prematurely1 and after having been opened should be kept covered when not in use4 ,,applying ,,glue ,all surfaces to which glue is to be applied should be warm and dry4 ,hot glue will chill if applied to a cold surface1 and if wood is being glued1 moisture will have the effect of clogging the pores of the wood4 ,heat dries and expands the pores1 allowing the glue-fibres to penetrate deeply1 thus insuring perfect adhesion4 ,at the same time there is danger of getting wood too dry1 making it absorb too much glue1 and too speedily4 ,this causes a very quick setting1 and may result in 8starving0 the glue joint4 ,some users on this account recommend adding a little moisture to the surface of stock1 by steaming or by application of a little warm water4 ,there is more or less uncertainty on this subject4 ,as a general conclusion it is safe to say that stock must always be warm2 surplus moisture must be expelled2 no 8green0 stock must be used4 ,here again1 as in so many other problems of the glue-room1 observation of results under actual conditions should be the guide to practice4 ,,securing ,,workers' ,,co-,,operation ,one more thing of extreme importance--the employer should do everything possible to secure the co-operation of every worker in the glue-room1 from the foreman down1 in using proper methods4 ,a little personal interest here will be rewarded a thousand fold4 ,provide your workmen with proper equipment1 which in itself encourages cleanliness1 and show them how the quality of work may be improved4 ,show them that an unclean1 ill-smelling glue-pot is unnecessary4 ,show them that there is a right way1 and a wrong way1 to prepare glue--and the right way is the way to use4 ,introduce system into the glue-room1 as into every other part of the plant4 ,many workers are still ignorant of modern glue methods4 ,it is the duty of the employer to know what the correct practice is1 and to see that it is employed in his glue-room4 ,,chapter ,v ,,modern ,,glue-,,room ,,equipment ,with the increased knowledge of the nature of glue1 and of proper methods of handling1 has come a great improvement in apparatus used4 ,the primitive way of melting glue was to heat it in an open pot over a fire4 ,no heed was given to the loss through evaporation2 nor to the scalding of glue2 nor to the dirty condition of the glue-pot1 and consequently contamination of fresh glue by the remains of former melts frequently occurred4 ,we say 8primitive0 methods advisedly in speaking of this old-time way of melting glue2 for in the light of modern knowledge such methods belong to a day gone by4 ,yet some glue-rooms still use the old open glue-pot1 and many others use apparatus which shows little1 if any1 improvement4 ,modern glue-room appliances are now available for every glue-room1 for every purpose4 ,no glue user1 large or small1 can afford to use any but modern1 scientific equipment4 ,the saving in time1 and in materials1 and in improved quality of the completed work1 and in the greater respect and increased efficiency of workers in the glue-room1 all these things result in quickly repaying the increased outlay required4 ,,only ,,copper1 ,,brass1 ,,aluminum ,,should ,,come ,,into ,,contact ,,with ,,glue ,the advantage of using copper1 brass1 and aluminum in glue-room appliances1 due to their self-cleansing properties1 already has been mentioned4 ,in apparatus designed for melting glue the use of copper1 brass1 and aluminum is absolutely required for economy and good results4 ,copper1 brass1 and aluminum are the only materials available that are not affected unfavorably by the action of acids in glue1 steam and water2 by boiler compounds1 dirt1 pipe-rust and sediment4 ,an iron agitator or stirrer in a glue-heater is corroded so quickly by the acids in glue1 water and steam that in six months it is unfit for use4 ,a brass agitator1 on the other hand1 will last practically forever4 ,so it is with every part of the glue-heater with which glue comes into direct contact4 ,the glue user who has had experience with galvanized iron heaters does not need to be told that the iron quickly is eaten away and the apparatus rendered unfit for use4 ,it is certainly the part of wisdom to invest in copper1 brass1 and aluminum equipment1 to which metals there is practically no 8wear-out40 ,glue-room equipment of iron is still sold1 but only because there are still some users who are so blinded by the initial small saving in outlay1 as not to see the saving that accrues in the end from using indestructible materials--and the additional saving due to good work and economy of glue4 ,a ,,scientific ,,glue-,,heater ,the facts already mentioned about the melting of glue should be borne in mind in choosing a glue melter1 or glue-heater--always remembering in particular that it is of utmost importance that the heating agent should not come into direct contact with glue1 and that the glue should not be overheated in preparation4 ,the glue-heater that has been proved most economical and efficient in wide-spread use has an air-tight glue chamber 7to prevent evaporation71 surrounded by a water-jacket 7to prevent burning or scalding glue71 the water in the jacket being heated either by direct injection of steam or by the use of copper heating coils4 ,electricity is also used successfully as a heating agent4 ,the heater is made of copper and brass throughout1 and is therefore not affected by the harmful effect of acids in glue1 steam and water1 dirt1 grease1 pipe-rust1 sediment and other harmful substances4 ,in this heater glue is reduced to a uniform and correct working consistency1 and with unusual speed1 if desired2 #e gallons of glue may be melted in less than #ae minutes1 and as much as #ej gallons in less than one hour4 ,it has already been noticed that excessive speed in heating requires a degree of heat that is injurious4 ,a thermometer is provided with this heater that gives accurate readings of the temperature within the glue chamber1 so that the heat may be turned off when the danger point of #aej ,f4 is reached4 ,,the ,,automatic ,,temperature ,,controller ,a still more recent and valuable improvement is the automatic temperature controller1 a thermostatic valve which operates automatically to keep the temperature in the glue chamber between #ade ,f4 and #aej ,f41 or at any temperature for which it is set4 ,not only overheating of the glue is prevented1 but expense of supervision is reduced4 ,the heater does not need to be constantly watched for fear glue will not be kept at correct temperature4 ,this particular heater is also provided with a brass agitator 7hand or power7 for keeping glue thoroughly mixed while melting1 and with a special faucet by means of which the melted glue is drawn off without dripping or clogging4 ,it is made in sizes from #b gallons to #ejj gallons liquid capacity1 and for use with any heating agent--gas1 electricity1 or steam4 ,an apparatus of this kind not only facilitates economical melting of glue1 by preventing evaporation1 waste1 formation of scum1 sour and dirty glue1 but it also insures uniform 8spread40 ,furthermore1 it is a great incentive to accuracy and cleanliness on the part of workmen1 encouraging them to good work by providing them with a neat and clean glue-melting appliance1 in contrast with the old-fashioned1 unsightly and ill-smelling 8glue-pot20 and providing them also with glue that has been properly prepared4 ,,keep ,,steam ,,away ,,from ,,glue ,above all1 keep steam away from glue4 ,some glue-melting devices are on the market in which glue is prepared by subjecting to the direct application of steam4 ,this produces only bad results4 ,all authorities are now agreed on this subject4 ,it is safe to say that the chief development in glue-room methods of the past ten years hinges entirely on the discovery of these facts3 that steam ruins glue2 that glue never should be heated above #acj to #aej ,f4 at the utmost2 that the other properties in steam--boiler compounds1 acids1 dirt1 pipe-rust1 sediment1 and grease--are absolutely injurious to glue4 ,do not let the argument of speed blind you to the damage resulting from the live steam type of dissolver4 ,if you want speed1 use a type of instantaneous dissolver that prevents steam from coming directly into contact with glue4 ,the very best practice1 the one generally recommended by experts1 is to heat glue slowly1 with a heat not above #acj to #aej ,f4 ,then the glue is in the very best possible condition for work4 ,the effect of acids is such that they have been known to turn a pot of good glue black4 ,,glue ,,spreaders ,in wood-working establishments where much glue is used1 it should be applied mechanically1 by means of glue spreaders4 ,some spreaders are made with ,brussels carpet covering for rolls1 but this is not good practice4 ,the carpet covering absorbs dirt quickly1 is difficult to keep clean1 is liable to tear1 is sure to stretch and eventually rots and wears out4 ,the simplest1 cleanest1 and cheapest method in the long run is to have rolls with corrugated surface2 even spread is thus assured1 and there is practically no 8wear-out0 to them4 ,in order to keep glue at right temperature during use1 it is best to have the glue-pans surrounded by heating coils4 ,these may easily be connected with the steam boiler or gas heater2 or electricity may be used4 ,a further improvement is to have the spreader connected with the glue-heater1 as then only a minimum quantity of glue need be carried in the pans4 ,by this method a quantity of glue sufficient for a day's work or half-day's work may be melted in the morning and maintained steadily at uniform thickness and temperature until used4 ,the melted glue is fed to the pans only as needed1 through open copper troughs4 ,glue pans should of course be made of copper1 for the reasons already mentioned4 ,another advantage is that copper pans are self-cleaning1 as glue does not adhere to this material4 ,spreaders may be had as a single-roll machine1 for coating one side of stock1 or as a double-roll1 for coating both sides1 or as a combination single and double-roll4 ,they may be operated by hand or with power4 ,when used with power a good operator can coat #ac1ejj lineal feet per day1 with a good machine4 ,the results with a glue spreader are largely due to the proper adjustment of the scrapers4 ,glue spreaders can be used to coat flats1 edges1 straights and mitres equally well4 ,for coating plain and straight surfaces1 use a solid roll4 ,for tongued and grooved pieces1 ,v-shaped stock1 dovetails and other irregular shapes1 use a brush roll4 ,some spreaders are fitted with combination solid and brush roll2 a very convenient and economical arrangement4 ,the spreaders should be kept scrupulously clean1 and also the brushes1 if any are used4 ,clean brushes by filling glue pan with hot water and revolving the brush in it until all the glue has been removed4 ,,clamps ,,and ,,presses ,after gluing1 the work should be kept under pressure for a sufficient length of time to insure perfect adhesion4 ,in the case of hide glues the time required is from three to four hours4 ,the time varies with variations in the glue1 in condition of stock1 and in temperature of room4 ,no general statement can be made to cover the case2 experience is the best guide4 ,either retaining clamps or presses are used4 ,pressure should be distributed as evenly as possible4 ,presses may be had in almost every style for every need--open on one side1 or on two sides2 for veneered stock2 sectional presses2 etc4 ,very excellent presses are being made of structural steel4 ,they are practically indestructible1 very efficient1 and yet simple in operation4 ,in selecting a veneer press equipment the amount of pressure per square inch must first be determined4 ,opinion varies with different manufacturers1 some using #ajj pounds1 some #bjj pounds1 per square inch4 ,the best general results are obtained by using #aej pounds per square inch4 ,all presses made with a #b-;inch screw should be designed to withstand a pressure of #h tons or #af1jjj pounds per screw4 ,to find the tonnage of press that you require1 multiply the length by the width of stock1 this by the pressure per inch you desire and divide the results by #b1jjj4 ,this will equal the tons pressure required4 ,the number of screws per press can then be determined4 ,,distributing ,,glue ,,in ,,large ,,plants ,glue is used in the wood-working industry mainly for making joints and veneers4 ,in large establishments1 where many workmen are employed1 a good plan for distributing the melted glue is to arrange a battery of small glue-pots1 or warmers1 strung along a pipe line running from the steam boiler or gas heater4 ,individual pots of copper which are filled at the central source of supply fit into cast-iron jackets1 kept warm by steam which comes from the pipe line4 ,the requisite temperature is thus maintained at minimum cost4 ,the valves may be so arranged as to cut off any warmer not in use1 avoiding waste of heat4 ,the arrangement is very satisfactory even in comparatively small establishments1 and may be adapted to any number of individual pots4 ,,advantages ,,of ,,electrical ,,equipment ,when steam is used as the heating agent1 only about one-fifth the amount of heat generated is actually used for heating the glue4 ,four-fifths of it radiates through the pipes and creates a heat so intense that the efficiency of the workmen is reduced fully one-half in summer4 ,with gas as the heating agent1 the same conditions are present as with steam1 plus the fire risk1 which in itself is so great as to make gas extremely inadvisable4 ,electricity is coming into greater favor every year1 with the improvement of electrical glue-heating appliances4 ,electricity is still too expensive to justify its use as a heating agent1 except for the exact purpose desired1 but modern electrical devices1 including the jacketed1 heat-retaining glue-pot1 make it possible to use electricity without waste4 ,the cost is less than either steam or gas and its advantages are so great that thousands of institutions are now using these 8fireless0 glue-heaters4 ,the best electric glue-heaters are made of copper and brass1 the greatest conductors of heat4 ,they require much less heat than any other pot and the heat is required for just about one-fifth the time1 owing to the heat-retaining jacket4 ,,chapter ,,vi ,,which ,,glue ,,to ,,use ,the answer to this question depends so largely on the individual conditions1 that only very general suggestions may be given4 ,we have already suggested the need of experimenting and accurately recording the results of using various kinds of glue4 ,once again1 your dealer will give you good advice nine times out of ten--and your own experience should afford the most valuable check on his suggestions4 ,in general1 the following glues are indicated3 ,wood joints--,high test hide glues4 ,they make strong1 firm joints1 which is extremely important1 as joints are subject to more or less tension2 and they set rapidly4 ,veneers--,a moderately high test mixture of bone and sinew or bone and hide4 ,the higher test glues set too quickly for this particular kind of work4 ,if a spreading machine is used1 avoid a glue that tends to foam4 ,sometimes foaming is caused by its spreading too fast4 ,overheating glue also tends to foam it4 ,this can be overcome by the addition of sweet oil or vaseline1 paraffine or wax candle1 but it is objectionable when veneering4 ,it is best to be sure you have a glue that will not foam4 ,your dealer can tell you what glue to use4 ,sizing--,use a glue free from grease and foam and one that flows freely4 ,paper ,boxes--,a quick-setting hide glue is indicated for setting-up4 ,for covering1 a lower test bone glue is preferred1 as it does not set so quickly4 ,paper box manufacturers are troubled more or less with foaming glue and can use the remedy suggested in the paragraph on veneers1 as this will not be objectionable in paper box work4 ,belting and ,other ,leather ,goods--,here the principal requirements are flexibility1 resistance to moisture and tenacity4 ,the higher test glues are generally preferred4 ,bookbinding--,for pasting covers1 a low-grade bone glue answers all requirements sufficiently well4 ,for rounding and backing1 where strain is exerted1 a high-grade hide glue should be used4 ,for ,emery ,purposes--,very high-grade glue that has been carefully prepared to eliminate all acids1 alkalies and impurities4 ,a good emery glue possesses superior water-absorbing qualities4 ,to test a glue for emery purposes1 soak an ounce in about five times its weight of water at room temperature for #dh hours4 ,if at the end of the time the water shows discoloration1 or if decomposition is evidenced by a disagreeable odor1 the glue is not adapted to emery use2 otherwise it may safely be used4 ,weigh glue after the operation1 to get an idea of its water-taking properties4 ,,how ,,much ,,to ,,pay ,,for ,,glue ,while the high test glues cost more per pound1 they go farther and do better work1 except in cases when their quick-setting characteristics are an objection4 ,how much you can afford to pay for your glue is a question that you must answer from your own observation and tabulation of results4 ,in certain lines it would be foolish to use a high-grade glue1 where the work would not benefit in proportion to the increased expenditure4 ,any attention given to the subject will be well repaid4 ,,keep ,,accurate ,,records ,always keep accurate records1 and base your future purchases upon the demonstrated comparative results already attained by the various glues you have used in actual practice4 ,no glue is good to use unless properly prepared4 ,a #af-;cent glue may be reduced to the grade of an #h-;cent glue by overheating4 ,the grade of the glue at the time it is used is the important thing4 ,do not by faulty methods of preparation impair the working quality of your glue4 ,a glue of moderate high-grade properly prepared is better for practical purposes than a high-grade glue whose working quality has been destroyed by excessive or prolonged heating4 ,,waterproof ,,glue ,sometimes it is desired to use glue with waterproof qualities4 ,glue is rendered practically waterproof by adding a small quantity 7about #a7 of ammonium or potassium bichromate to the glue liquid4 ,upon hardening1 the glue then becomes waterproof4 ,adding a small quantity of formaldehyde to the liquid glue will help it to resist the action of water after it has dried for some time4 ,others suggest dissolving glue in an equal quantity of water and adding about as much linseed oil as water1 with the aid of heat1 until a jelly is formed4 ,this mixture is said to be practically waterproof4 ,a patented process has recently been put out for which the claim is made that it can be applied to any glue irrespective of grade or make1 rendering it absolutely waterproof4 ,the result is attained by mixing the glue with certain chemicals in specified proportions1 and then adding a certain amount of formaldehyde4 ,any amount of glue can be treated and the process is said to be most effective4 ,,vegetable ,,glue ,of recent years efforts have been made to find a substitute for animal glue4 ,the effort has met with success to a certain extent for particular kinds of work4 ,probably the newest addition to the list of vegetable glues is the mineral glue-silicate of soda4 ,liquid silicates were first sold for the manufacture of soap4 ,in recent years certain forms have been used for light adhesive paper work4 ,it is used in places where glue is too slow setting4 ,,quick ,,setting ,,glues ,when a glue is desired to set very quickly the manufacturer can usually furnish glue with the setting qualities desired for the particular work in hand4 ,if this cannot be done1 for any reason1 remember that the temperature of the glue is an important factor4 ,a low temperature aids in quick setting4 ,some paper box manufacturers have had successful results in quick setting by adding a small quantity of turpentine to the liquid glue4 ,some add silicate of soda4 ,,flexible ,,glues ,specially made glues are supplied by manufacturers for work in which flexibility is needed4 ,an easy way to increase the flexible quality of glue is to add a little glycerine to the liquid glue4 ,the ,republican ,publishing ,co41 ,hamilton1 ,ohio ,,transcriber',s ,,notes ,inconsistent hyphenation has been standardized throughout4