,,the ,,institute ,,of ,,industrial ,,research ,allerton ,s4 ,cushman1 ,a4 ,m41 ,ph4 ,d41 ,director1 ,in ,charge ,division ,metallurgical ,problems4 ,henry ,a4 ,gardner1 ,assistant ,director1 ,in ,charge ,division of ,paint ,technology4 ,n4 ,monroe ,hopkins1 ,ph4 ,d41 ,in ,charge ,division of ,electrical ,engineering and ,electrochemistry4 ,chas4 ,a4 ,crampton1 ,m4 ,d41 ,ph4 ,g41 ,in ,charge ,division of ,food and ,drug ,products4 ,g4 ,w4 ,coggeshall1 ,ph4 ,d41 ,in ,charge ,division of ,mill ,problems4 ,chas4 ,baskerville1 ,ph4 ,d41 ,f4 ,c4 ,s41 ,in ,charge ,technology of the ,rarer ,elements4 ,copyright1 #aiaa1 ,the ,institute of ,industrial ,research ,,the ,,institute ,,of ,,industrial ,,research ,,the ,,preservation ,,of ,,the ,,exterior ,,of ,,wooden ,,buildings ,,by ,,allerton ,s4 ,,cushman1 ,director ,,the ,,institute ,,of ,,industrial ,,research ,,and ,,henry ,a4 ,,gardner1 ,asst4 ,director ,,in ,,charge ,,division ,,of ,,paint ,,technology1 ,,the ,,institute ,,of ,,industrial ,,research ,illustration ,,washington #aiaa ,,washington1 ,d4 ,c4 ,,press ,,of ,,judd ,,detweiler1 ,,inc4 #aiaa ,,preface4 ,for a number of years the writers have been making a study of industrial problems and have been publishing the information which they have acquired1 regarding the value of various structural materials1 for the benefit of consumers as well as producers4 ,the ,institute of ,industrial ,research has received so many requests recently for information in regard to just what paints should be selected for the protection and decoration of houses and other buildings that it has seemed best to sum up the subject in the form of a special pamphlet or bulletin4 ,it is only after years of investigation work carried on by the authors1 both separately and in co-operation1 that any review of the work has seemed possible1 for only recently have the results of tests carried on in a number of different localities seemed to justify a definite opinion in regard to the best selection of exterior paints4 ,no attack on any one paint material is here included1 but the value of each has been carefully weighed1 and the attempt is made to discuss them in the light of experience and knowledge4 ,it is the authors' intention in this bulletin to put into the hands of architects and paint users who may not be thoroughly familiar with the technical properties of paint materials1 information which will enable them to make a proper and intelligent selection of paints for the preservation and decoration of the exterior of wooden buildings4 ,the ,preservation of the ,exterior of ,wooden ,buildings ,lumber and its ,relation to ,paints3 ,the proper choice and treatment of lumber is one of the most important problems which the builder as well as the painter has to face4 ,when about to build a dwelling1 barn1 or other structure made principally of wood1 the question is sure to arise in regard to what variety to select so as to get the maximum service and money value4 ,the locality in which the structure is to be built must often have a bearing upon this question4 ,while it is true that the painting of each type of wood demands the special consideration of the painter1 it is also true that the study of paints for wood protection points toward the production of a paint that will give satisfactory results under all conditions and on all grades4 ,it is the writers' opinion that a paint may be made that will be perfectly well suited for the preservation of every species of wood1 provided the paint is properly treated in the hands of the skillful and intelligent painter1 who can produce lasting results on almost every type by varying the proportion of thinners and oil in the various coats4 ,the painter who uses the same paint on soft pine1 and again on hard pine1 without making a special study of how to reduce the priming coat for the hard pine1 will be likely to get inferior results on the latter4 ,in case of failure1 the natural impulse is often to place the blame upon the paint1 whereas the real responsibility may rest upon the painter's lack of knowledge4 ,note4--,for a more detailed account of the lumber question1 see ,modern ,lumber as a ,problem for the ,painter1 read by ,john ,dewar1 at the ,convention of ,master ,house ,painters' and ,decorators' ,association of ,pennsylvania1 ,january1 #aiaa1 ,pittsburg1 ,pa4 ,photographs ,showing ,different ,forms of ,decay ,exhibited by ,improperly ,made ,paints ,illustration3 ,blistering ,illustration3 ,chalking ,illustration3 ,checking ,illustration3 ,cracking ,illustration3 ,scaling ,illustration3 ,general ,disintegration ,signs of ,paint ,failure3 ,those who are responsible for the care and maintenance of property are familiar with the condition of surface presented by almost all wooden buildings or structures which have been improperly painted with inferior paints4 ,chalking or flouring are terms used to describe the condition of a paint surface which has deteriorated within the paint film4 ,the formation of minute fissures1 generally spoken of as checking1 as well as the effects best described as cracking1 scaling1 peeling1 and blistering1 are other signs of failure which cause paint coatings to present an unsightly appearance1 and which point inevitably either to the use of improperly made paints or to improper application4 ,the cause of these conditions is not difficult to understand when even a brief study of the character of the materials entering into the composition of a paint has been made4 ,it is1 however1 a fortunate circumstance that the proper admixture of different types of pigments enables us to correct the strong tendency exhibited by special pigments to rapidly deteriorate in an oil film4 ,this point will be more fully discussed in a later paragraph4 ,requisites of a ,good ,paint3 ,progressive manufacturers are aiming to produce a paint which will show1 under the widest range of conditions1 good hiding power1 adhesiveness1 freedom from internal strains1 permanency of color1 relatively high imperviousness to moisture1 sufficient elasticity to prevent scaling or cracking when subjected to expansion or contraction1 and freedom from the chemical action which results in deep checking or excessive chalking4 ,such a product as this cannot be attained1 in the writers' opinion1 by the use of any one pigment in linseed oil4 ,in order to meet all the demands as stated above1 there should be in an economical and durable paint a proper percentage of the various pigments which1 united1 will tend to correct each other's faults1 and thus produce a durable paint coating of maximum efficiency4 ,the ,composition of ,paints3 ,as is well known1 a paint is a mixture of one or more pigments and a vehicle which acts the part of the spreading and binding medium4 ,up to the present time the vehicle portion of paints has generally been made of linseed oil1 admixed with some volatile thinner1 such as turpentine4 ,the subject of oils and paint vehicles will be discussed more fully later on4 ,physical ,properties of ,pigments3 ,the pigment portion of a paint for use on barns and farm buildings may1 if desired1 be composed of properly selected iron oxides or other colored pigments1 even containing in some cases a moderately high percentage of silica1 clay1 or other inert materials1 and give perfectly satisfactory results4 ,for the preservation and decoration of dwellings1 however1 the pigment portion of paints is generally made as a whole or in part of the more expensive white pigments1 such as white lead and zinc oxide4 ,the relative values and properties of these white base pigments will now be taken up4 ,white ,leads3 ,white lead1 either of the corroded or sublimed type1 is perhaps the most generally used of all the white pigments as a paint base4 ,corroded white lead is a basic carbonate of lead1 while sublimed white lead is a basic sulphate of the same metal4 ,both of these types are white1 and admirably adapted as painting materials4 ,they take relatively the same amount of oil and spread easily1 producing paint films which are highly opaque and which1 therefore1 hide efficiently the surface upon which they are placed4 ,sublimed white lead is a relatively finer pigment than corroded white lead1 and seems to show a tendency to chalk to a greater extent upon exposure to the weather4 ,corroded white lead is more alkaline1 however1 than sublimed white lead1 and when used alone with linseed oil generally shows a tendency to chalk to a considerable extent in a short time and to show deep checking1 thus permitting the admission of moisture4 ,the alkaline nature of this pigment produces considerable action upon certain tinting colors and results in fading or darkening1 when mixed with delicate greens or blues4 ,the use of white lead has been condemned in some parts of this country as well as abroad1 because of its alleged poisonous properties4 ,while it is true that lead poisoning may occasionally occur in some factories where the workman and his conditions are not properly safeguarded1 it is1 nevertheless1 a fact that lead poisoning very seldom occurs among painters of experience and cleanly habits4 ,carelessness in mixing white lead is1 fortunately1 a practice almost obsolete among modern painters4 ,the use of paints already ground in oil by means of machinery to a pasty condition1 allowing easy working and reducing1 obviates the danger of lead poisoning from any such cause as this1 even though the percentage of lead in such paints is in preponderance4 ,recent efforts that have been made by the legislatures of certain ,states to brand lead paints as poisonous are not only unnecessary1 but show a complete ignorance of the problem4 ,zinc ,pigments3 ,another pigment which has proved itself of great value to the painter is zinc oxide4 ,the use of this pigment may be said to have almost revolutionized the paint industry of the world1 and its increased consumption during the last ten years is sufficient evidence of its value as a painting material4 ,zinc oxide is produced by oxidation and sublimation of zinc ores and is not only extremely fine1 but of great whiteness4 ,it has good hiding power1 although not quite so great as that shown by the white leads4 ,it tends to produce a glossy surface1 making it especially valuable for use on interior work and in enamels4 ,when used alone it has the effect of hardening the oil film in which it is enveloped1 and upon long exposure causes cracking and scaling4 ,however1 when the sublimed or corroded white leads are properly combined with zinc oxide1 a more durable surface is produced1 the shortcomings of each pigment being overbalanced by the good properties of the other4 ,the proper combining properties of zinc oxide with white lead may be said to vary between #bj to #ee per cent of zinc oxide for paints designed for exterior use4 ,in the opinion of the authors1 lead and zinc pigments in the above percentage1 properly blended and ground1 make paints of far better wearing value than can be produced with either white lead or zinc oxide used alone4 ,zinc ,lead3 ,zinc lead1 a pigment sublimed from mixed lead and zinc ores and containing about equal proportions of zinc oxide and lead sulphate intimately combined1 as well as leaded zinc1 a produce similarly produced1 but with the zinc oxide running about #ge per cent1 are white base pigments of value1 which are used to a considerable extent4 ,they are generally slightly off color1 however1 and are therefore used most largely in paints which are to be tinted in various colors4 ,lithopone3 ,lithopone1 a pigment produced by precipitation1 and consisting of zinc sulphide and barium sulphate1 is of great value in the manufacture of interior paints4 ,on account of its liability to darken and disintegrate1 however1 it is seldom used on exterior work1 although recent tests have shown that when used in combination with zinc oxide and whiting1 it gives very promising results4 ,crystalline ,pigments and ,their ,use3 ,barytes 7barium sulphate71 silex 7silica71 whiting 7calcium carbonate71 gypsum 7calcium sulphate71 asbestine 7silicate of magnesia71 and ,china clay 7silicate of alumina7 are white crystalline pigments which1 when ground in oil1 become transparent4 ,all of these pigments possess the property of strengthening a paint film made of white lead and zinc oxide1 and often increase the durability of such a paint4 ,barytes1 silica1 and ,china clay are especially valuable for this purpose4 ,asbestine1 because of its needle-like structure and low gravity1 prevents settling and acts as a reinforcer of paint films4 ,whiting or calcium carbonate should be used when zinc oxide is in excess in a paint1 so that the hardness of the paint may be overcome4 ,a white paint must be possessed of sufficient opacity to efficiently hide the surface upon which it is placed1 when three coats are applied for new work or two coats for repainting work4 ,mixtures of the white leads and zinc oxide1 with the latter pigment running not over #ee per cent1 will easily produce such a result and wear well4 ,it is generally deemed advisable1 however1 by most manufacturers to take advantage of the excessive opacity of such mixtures1 which allows the introduction of moderate percentages of those inert pigments which give greater strength and other desirable features to a paint4 ,the percentage of natural crystalline inert pigments to add to a white paint made of lead and zinc must1 however1 be moderate and insufficient to detract materially from the hiding power of the paint4 ,note4--,pigments such as silica1 barytes1 ,china clay1 and asbestine are thoroughly inert4 ,recent investigations have proved that they accelerate the drying of linseed oil1 but this is not due to any chemical action they exert1 but rather to their physical action in distributing the mass of oil in which they are ground1 and thus allowing a greater surface to be exposed to the oxygen of the air4 ,it is also possible that some of the inert pigments may stimulate oxidation by catalytic or contact action1 although they are not chemically active in themselves4 ,white-,paint ,formulas3 ,from these conclusions which have come from wide experience in the testing of paints under actual service conditions1 there can be recommended to the buyer of paints and to the manufacturer and master painter those machine-mixed paints in white1 made by reputable manufacturers1 the composition of which will show a mixture of white lead and zinc oxide1 with the latter pigment within limits of between #ae to #ee per cent1 and especially the same mixtures reinforced with the moderate percentage of crystalline inert pigments referred to above4 ,tinted paints possess greater hiding power than white paints1 and the above proportions would be somewhat changed for a tinted paint containing any percentage of coloring material4 ,tinted paints are1 moreover1 far more serviceable than white paints1 as will be shown later4 ,mill vs4 ,paddle3 ,the mixtures under consideration should be ground in linseed oil by the manufacturer1 through stone or steel mills1 to a very fine condition1 as it is only through proper grinding that the pigments can be properly blended4 ,the mixing of paint by hand is1 fortunately1 to a large extent a thing of the past4 ,the uneven lumping of hand-mixed paints are often the cause of their failure4 ,such ancient and crude practice should be avoided by every painter1 for it is more economical to obtain semi-paste paints1 properly ground by machinery1 to such a condition that they may be easily broken up and tempered4 ,such paints may be reduced to the proper consistency with oil and volatile thinner for application to any kind of wood4 ,in the opinion of the writers1 a majority of the paints sold by reputable dealers and made by reputable manufacturers in this country are not only made from the best linseed oil and highest-grade pigments obtainable1 but are put up in a form ready for the painter to thin down with full oil or turpentine reductions1 either for priming work or to be used without reductions for finishing coats4 ,the large metropolitan painter who wishes to make his own tints and shades may1 however1 prefer to have his mixed pigment paint ground by the manufacturer in heavy paste form for certain purposes4 ,results of ,field ,tests3 ,a careful analysis of the results of field tests which have been carried on in different parts of the country would be far too voluminous for insertion in this bulletin4 ,the official findings of special committees of inspection have already been published in special reports4 ,whereas there may still remain ground for some difference of opinion in regard to the interpretation of the results obtained on the various test fences1 there can be no doubt that considerable information of the highest value has been yielded1 both to the producers and consumers of paints4 ,one of the principal results obtained from these tests has led to the opinion expressed above by the writers1 that better results can be obtained by a proper mixture of selected pigments than by the use of any one pigment in linseed oil4 ,this conclusion has also been reached by engineers of the ,united ,states ,navy1 and1 as a result1 the specifications of the ,bureau of ,yards and ,docks for paints made of straight white lead and oil have recently been changed to call for white lead combined with upwards of #ej per cent of zinc oxide4 ,many engineers and master painters have interpreted the results of the tests in the same way1 and the attention of the authors has been called to a number of opinions which show that the tendency of demand among those who are properly informed is for a high-grade combination type of paint rather than for any single pigment paint4 ,color3 ,the selection of the color for a dwelling or other structure is a matter that depends largely upon the good judgment and taste of the owner1 combined with the advice of the painter4 ,one point1 however1 should be impressed upon the mind of both1 namely1 that ,,practically ,,all ,,shades ,,or ,,tints ,,made ,,upon ,a ,,good ,,white ,,paint ,,base1 ,,through ,,the ,,use ,,of ,,permanent ,,tinting ,,colors1 ,,will ,,better ,,withstand ,,exposure ,,to ,,the ,,atmosphere ,,than ,,the ,,white ,,base ,,used ,,alone4 ,owing to the cheerful effect produced by the use of white paint on dwellings1 a very large quantity of white will continue to be used4 ,if these white paints are designed in line with the suggestions brought out above--that is to say1 if the white lead bases are properly reinforced with zinc oxide and other pigmentary materials--better results will undoubtedly be obtained1 as far as appearance and durability is concerned1 than if white lead had been used alone4 ,the consumer should remember1 however1 that more durable results will be obtained by the use of tinted paints4 ,reductions and ,thinners3 ,turpentine1 with its sweet odor1 high solvent action1 and wonderful oxidizing value1 has always taken first place among the volatile liquids used for thinning paints4 ,wood turpentines1 produced from the steam distillation of fine-cut fat pinewood or from the destructive distillation of stumpage and sawdust1 have been refined in some cases1 by elimination of odor and toxic effects1 to such purity that they are equally as good as the purest grades of gum turpentine1 and their use is bound to increase in the paint industry4 ,the painter and manufacturer have come to understand that certain grades of asphaltum and paraffine distillates are equally as satisfactory as turpentine for use in paints for exterior purposes4 ,those volatile oils which are distilled from crude oil with either a paraffine or asphaltum base and possessed of boiling point1 flash point1 color1 and evaporative value approximating similar constants of turpentine1 are excellently suited to partly1 and in some cases wholly1 replace turpentine in exterior paints4 ,a little additional drier added to paints thinned with these materials will cause oxidation to take place in the proper time4 99 99 99 99 99 ,prominent master painters,a have shown that benzol1 a product obtained from the distillation of coal tar1 differing from benzine1 a product obtained from the distillation of petroleum1 is a valuable thinner to use in the reduction of paints for the priming of resinous lumber such as cypress and yellow pitch pine4 ,the penetrating and solvent value of benzol is high1 and it often furnishes a unison between paint and wood that is a prime foundation to subsequent coatings1 preventing the usual scaling and sap exudations1 which often appear on a painted surface4 ,because of the great solvent action of benzol1 however1 this material should never be used in the second and third coatings4 ,these facts will doubtless interest the ,southern painter1 who has so much wood of a refractory nature to paint4 ,a ,dewar1 ,titzel et al4 ,oils3 ,the increasing cost of linseed oil has raised the interesting question as to whether or not it is good practice to use an admixture of other oils in connection with it1 in high grade paint coatings4 ,strong differences of opinion will probably be found in regard to this question1 and undoubtedly further investigation work is necessary in order to decide it4 ,a number of different oils have been proposed for the purpose1 of which1 perhaps1 soya bean oil is the one which has been most prominently discussed4 ,no definite formulas1 however1 should be recommended until the results of investigations which are now being carried on are in hand4 ,a systematic series of test panels is now being erected in ,washington1 ,d4 ,c41 on the grounds of ,the ,institute of ,industrial ,research1 which are designed to gather data covering just this point4 ,the flax crop conditions have been most discouraging during the past two years1 and the natural shortage of seed has caused a rise in the price of linseed oil1 which has necessitated a rise in the price of paint4 ,the added protection to be secured1 however1 through the frequent application of paint far outweighs any increased cost which has been caused by the rise in price of the raw commodities entering into the composition of paint4 99 99 99 99 99