Document 2qDzbv8z9bYVz4BJDkOQm3jx5

EXTERIOR HOUSE PAINT y S. 'WERTHAN Rcpnnt of a L*ctv/t Praientad Bafort Gu on Point TtehnoJogy af Wayna Umvtnitjr, Delia t, Michigan Reprinted from OFFICIAL DIGEST Federotion of Point end Varnish Production Clubs June, Nineteen Hundred Forty-nine 0007-SWP-043899 N23306 i Exterior House Paint* By S We r t h a n The New Jersey Zme Company (of P For the purpose of this paper I will consider house to the protective and decorative coatings used on surfaces which contain as their major vehicle component an unb further differentiate them from some ol the other oil veh such as metal protective, barn, trim and trellis, etc., pain discusstun to paints that contain an appreciable percent pigment. The painting of buildings and other structures is n from before the beginning of history, but painting for pre White lead, the first while opaque pigment to be used known to the early Romans Pliny in the first century facture. The early artists prepared their own paint by ment with oil or other medium While the records do n its first use as a house paint, it apparently was someti teenth century. The first white lead plant in the Unite Philadelphia in 1804 by Samuel Wetherill and Sons W produced about the middle of the century. The firs mixed paints are commonly accredited to D. R Averil who in July, 1867 patented a paint of this type and be and sale. The prepared paint industry, as a real indust started until the late seventies or the early eighties. It is interesting that although, during the past hal been many developments and changes in house paint f products never entirely replaced the old and the various used today. These include : 1 Straight White Lead Paints 2. White Lead-Zinc Oxide-Inert Paints 3. Lithoponc-Zmc Oxide-Inert Paints 4 Zinc Sulfide Pigments-Zinc Oxide-Inert Pai 5. Titanium Pigments-White Lead-Zinc Oxide 6. Titanium Pigments-Zinc Oxide-lnett Paints Resides changes m the composition of the pigm been a few changes in the composition of the nonvo straight raw linseed oil to combinations of various typ heavy bodied oils. A combination of basic carbonate of white lead, lin and drier was the first exterior house paint to be ge a painter no longer buys the dry basic carbonate nf lead and reduces it to paint in his shop, some continue to ma * An addraaa at Warn* UnlvcnUr a part of th*lr Tec under the aueplr** of the Detroit Paint and Varahh Production Club Vafinih and L**i)ur Aaaorlalton 0007-SWP-000127250 by reducing lead-in-oit paste with linseed oil, \okatile thinner, and liquid drier as their grandfathers did fifty years ago While zme oxide was also reported by Pliny, there is no mention of it hemg used in paint until late m the eighteenth century. Apparently some was used in house paint in America about 1830, for it is recorded at about that year the house of Dr Fowler, m the vicinity of Franklin, New Jersey, was painted with zinc oxide made from the zinc ore deposits far which that region is famous. There is no record of the type of vehicle used About the same time, the Frenchman, Leclaire, started the manufacture of zinc oxide and the promotion of its use in paint in place of white lead because of its nontoxic qualities and the retention of its brilliant whiteness even in the presence of sulfide gas It was not long until zinc oxide ground in a stand oil (heavy kettle bodied oil) vehicle was being used in Europe on both ex terior and interior wood surfaces Based on the limitations placed at the start of this article, this paint (Old Dutch enamel) cannot be considered a house paint Still it was not long until painters, recognizing the merits of zme oxide, added some to the white lead in preparing their house paint Thus was bom the lead-zinc type of house paint This was also about the time that the manufacture of ready-mixed paint started. The grinder, who had been marketing various brands of white lead and zme oxide pastes, was well informed regarding the blending of these two white opaque pigments and extending them with barytes and the sili ceous inerts This was the official birth of the White Lead-Zinc OxideInert mixed paint. In reality, the painters had for some time, unknowingly, prepared their own mixed pigment paint The late George B Heckel in "The Paint Industry--Reminiscences and Comments" describes in hs inimitable st>le the period of "laissez faire" in American paint manufacturing when under such descriptions as *'We guarantee the white lead in this package to be absolutely pure," tlie Basic Carbonate of Whit** Lead h i the wlnie lead j>astcs varied from 100 to 0 per cent of the pigment Two typical brands contained approximately 62 per rent IK'W L--28 per cent zme oxide--10 per cent barytes and 25 per cent B C W L --25 per cent zinc oxide--50 per cent barytes, respec tively Strange as it then seemed, frequently the results obtained by painters with these pastes were superior to those obtained with straight white lead pastes But the excessive use of inerts because of their low cost in ready mixed paints resulted m the opinion that the presence of any inert was a sign of inferior quality. Although it has long teen established that an exterior paint containing the correct types of inerts is superior to an inert-free paint, the impression still prevails that inerts are used only to lower cost In 1920, after protracted pigment and paint investigations, our Com pany developed and recommended to the industry Lilhopone-Zinc OxideInert paint. For many years prior to this time, lithoponehad been used as the basic white opaque pigment for interior paints Because the lithopones of * that time were light sensitive, tended to darken when exposed to sunlight, they had found little use in exterior paints In 1919, Albalith. a light resis tant hthopone, was developed, thus providing a hthopone suitable for use in exterior paint. The suggested paints contained several innervations in ex terior house pamt formulation, which, although known to many chemists, 2 had never been promulgated These formulations contai The unc oxide could be either a lead-free or a leaded gra grade of zme oxide was used, the pamt contained no lead lead-less ready-mixed paint. The work of our laborato siliceous inerts, such as silex, fibrous magnesium silicate, mica, impart definite benebcial properties to the paint abuse of the use of inerts or extender pigments had dev paint containing them, we did not hesitate to proclaim recommend 20 per cent in the lithopone-zinc oxide p studies also established that some heat-bodied oil in th the application, flow and film properties of pamt, and it that 10 per cent of the oil be kettle bodied oil of *`Q" visco paints, since they possessed higher-hiding and were low lead-zinc inert paints, met with considerable favor. At about the same time, titanium-barium pigment wa manufacturer Similar to hthopone, it is a composite pigm sulfate and titanium dioxide instead of barium sulfate and ing the twenties and thirties, many exterior house paint containing titanium barium pigment They contained b or at least one of them and usually some siliceous inert T to have a slight advantage over hthopone paint in hiding p a tendency to replace hthopone by high strength fithopo which had become commercially available. With the advent of titanium dioxide, the trend was t lum-banum pigment with titanium dioxide and the high inerts. This resulted tn improved and lower cost pain advantages of the siliceous inerts, the white pigment ma the paint manufacturers a zme sulfide composite pigmen was a combination of water ground mica and nbrous and a titanium composite pigment containing magnesium ert base Faints were formulated using either of these pi zinc oxides Another composite titanium pigment in w is anhydrous calcium sulfate became available. Althou pigment was limited almost entirely to interior paints, the rutile titanium dioxide type of pigment, there has te it in exterior house paint. Although, as has been mentioned, paints containing ous types of pigmentation are still being manufactured formulations today contain a combination of titanium d zme oxide, and inerts; or titanium dioxide, zinc oxide a Contrary to the many variations in the compositio there have been few changes in the vehicle. The comb seed oil, turpentine, and liquid drier, used originally, c without modification excepting that a boiled (one conta fined linseed oil might be substituted for the raw oil or p the turpentine The first and only modification up to the composition of the vehicle was the previously mentio a small percentage of the raw oil by kettle bodied oil F provements were undoubtedly retarded by one or two ill- 3 m enamelucd type vehicles which resulted in some disas To conserve oil during the war, the Government, on the a better informed paint technicians, compelled the paint m more heavy hodicd oil and volatile tlmnirr in their exte Thus was broken down the supposition that the oil in pamt must lie raw linseed oil The superior results that with the bodied oil paints fiave led to a more general us has also been demonstrated that replacement of a portio by other drying oils need not be detrimental (if nerally cent of the oil in today's highest grade rxterioi house oil, and this oil may be linseed or some other type of dr use of alkyds and other types of resin vehicles is licing j merits have not been established Paint films being organic coatings naturally deterio to the elements, the method and rate of this deteriora \ service obtained from the paint The large variety of e in use today may be partly attributed to the lark of a i relative importance of their different properties Anoth the paint's properties are only one factor, and frequen determining the service that will be obtained from the i are the type and condition of the surface to which the p application, the climatic conditions under which it is ap the weather and other conditions to which the him is I many laboratories have made extensive investigations to I for exterior house paint, no one has developed a satisfa ation. While there are tests for specific properties, the depend on actual exposure tests (panel or house) to de that may be anticipated from a paint. An exterior house paint serves a dual purpose, th and the beautiheation of the surface to which it is applie of the paint film includes the progressive disintegration o by chalking, sloughing, checking, and cracking, and fai under surface, such as blistering, peeling, and scaling of erties, besides these integrity factors, that influence the film are degree ol retention of gloss, color (white or tint It seems opportune at this time to discuss the relatio of the paint to its various properties. We will consider the pigment, the composition of the vehicle, and the rat the binder in the dry film Although exterior house pa not been a definite scientific process, there are certai reasons for the combinations oVpigments that have been consider some of the facts that are known regarding the by the various pigments to the paint fi|M I.--Magnified cron-lection driving* Mmtint* the c characterrlticl that hart lakrn piact at hoate paint* hare eeolvf matin Cl icnlamn A > rnla composite figment famtl (colam iltmghing 00 of the older faint has hem reflaeed by balance Ifolied tfonon in modrrn patnlt, maitint ponthlt a rotting that daring in tarter life hat aim learn a jmender joandatum for re ing! art from The blew leeiey Zinc Company's motion pietnr l tJuifj 0007-SWP-000127252 5 All of the white pigments {titanium, zinc sulfide, zinc oxide, and lead) impart opacity or hiding, although they differ appreciably in this property. On a weight bans, pure rutile titanium dioxide rates highest and whitt lead Inwest When white lead and nine oxide woie the only opaque white pig ments. their opacity was a major consideration m their use, hut today with the much higher hiding titanium and zinc sulfide pigments available, their contribution to the paint opacity is a minor consideration lor the inclusion of Irad and zinc m the pigmentation The characteristics that the various white pigments imparl to a linseed ml paint have been determined hy weathering tests For a number of years, our laboratory has exposed many series of claplxiard test panels painted with single and mixed pigment linseed oil paints, covering the various pigments and combinations of pigmrnts used in exterior house paints. The weathering characteristics of the films have proved very enlightening. I will only take time to mention a few of these characteristics. During exposure to the weather, the straight basic carbonate of white lead paint film accumulates dirt, becoming increasingly dirty. They also are darkened by sulfide fumes After about one vear nf exposure, a characteris tic crowfoot type of checking starts to develop With continued exposure, these checks increase in depth and severity and form little islands of film The exposed layers of the film flake off in small pieces taking surface dirt with them Thus neither a uniformly dean nnr attractive appearance is obtained In general, the cohesive strength of the film is less than the ad hesion of the film to the wood surface, so over a numlier of years a portion of the film remains It is this property that has resulted in a continued ac ceptance nf this paint The film has little resistance tn mildew, and this type of discoloration may be encountered in localities where mildew is prevalent The tinted paints do not fade but darken and develop a muddy appearance. The weathering process is slightly different in the case or basic sulfate of white lead The basic sulfate film is weaker than the basic carbonate paint film It does not develop visible checks, but the surface layer disintegrates and sloughs During early exposure, the film holds dirt, hut goes through cvcles of cleansing due to the sloughing of the exposed surface of the film While the film does not develop the pronounced checks and cracks of the It C W I- film, its taihire to wood is more rapid The film is also susceptible to mildew and sulfide darkening The tinted film tends tn fade The zinc oxide film is much stronger than either nf the lead films. There is very little apparent surface disintegration and the film retains its glnss over a long period of exposure. The film becomes progressively dirty es|iccially during the winter months. Therews a tendency for the traces of acidic gases in the atmosphere to react wilh the surface particles ol zinc ox ide m the film to form soltihle salts or snaps, which with rain act as cleansing agents While the film remains intact dining many years of exposure, it eventually develops cracks and ultimately pieces nf the film flake from the wood Zinc oxide possesses fungistatic properties. and thus the film is resis tant to mildew growth The tinted film holds its tint very well (the best of all the white pigment films) : the tint diies not fade hut shows a slight ten dency to heroine more intense. 6 \ leaded zinc oxide film is a strong film hut not so s free z.inr oxide film The film shows good gloss retention, a ly slight surface disintegration develops. Ultimately, as lead-free zinc oxide, cracking ami flaking of the film from The film shows less dirt retention and belter cleansing ch the lead-free zinc oxide film It is also resistant to the g The tinted film is definitely poorer than the lead-fret zinc retention; it shows a slight tendency to fade (You note t istics of the leaded zinc oxide paint film are what would be the film characteristics of its two pigment components.) The zinc sulfide pigments produce weak films, althoug what with the inert component Straight zinc sulfide produ film, followed by high strength lithopone, lithopone. and th cate base pigment, which is the weakest They all fail by erosion of the film The rate ol erosion of the films is in their strength, except that, due to the reinforcing properti base, especially the mica, the erosion of the siliceous bas delayed The erosion keeps the films quite clean The film high resistance to mildew, especially in the case of the s ment in which magnesium silicate appears to he a food for The discoloration of the film caused by copper metal is m the case of other white pigment films The anatase titanium dioxide pigments produce t films of the white opaque pigments, In the case ol these p of the composite pigments tend to be stronger than that of ium dioxide They all fail by erosion or sloughing of the anatase titanium dioxide and the magnesium silicate ba chalk the fastest and generally there is a heavy layer of re the surface of the film. Usually only one year is require chalk to the wood The rapid chalking results in good c anatase titanium dioxide rating highest among the white cleansing characteristics and maintenance of whiteness barium and calcium base pigment films chalk and erode sli but tend to hold more dirt and to develop cracking or slou anatase titanium dioxide pigment films are susceptible to m the calcium and magnesium silicate base pigments. The dioxide paints art the poorest of all the white pigment p tention. The films fade severely. The rutile titanium dioxide pigments produce strong anatase pigments. The rutile titanium dioxide paints vary type and rate of weathering depending on whether they co or non-chalking grades and the straight titanium dioxide o ment All nf the rutile titanium dioxide paint films chalk d the corresponding anatase pigment films. In general, th rapid enough to prevent the accumulation ol dirt. This photogenic yellowing results in the films during exposure n bright whiteness ol the anatase pigment films. This dev film whiteness is especially prexalent in the nonchalkin titanium dioxide The slow erosion of this grade results 7 for the film The pigments are susceptible to mildew, ilie calcium basechalk resisting grade produces paint films more susceptible than any other white pigment films Also, the tendency br tins pigment film to retain dirt is very pronounced The rutile litauiiiui pigment paints possess definitely Iletter tint retention than the analase and rate nest to the line sulfide pig ments They tend to both lade and to become muddy Inerts such as whiting, calcium sulfate, silica, and magnesium silicate in linseed oil develop practically no hiding They offer little protection for tile linseed oil binder so the films fail rapidly In the chemically nonreactive extender, such as silica and magnesium silicate, the bond between the inert and the oil binder is very weak, and the film failure is by disintegration or chalking In the case of the calcium pigments, whrrc soap formation may occur, a stronger bond between the pigment and hinder exists and disintegra tion may l>c accompanied by checking and cracking. None of these extender pigments possess fungicidal properties, and some are actually food for the mildew fungi In general, inerts have slightly detrimental effects on tint retention Waler-giound mica is an inert that warrants separate consideration l.ike the other siliceous inerts, it develops practically no hiding and pro duces weak films Hut because of its thin laminar particles, it apparently pro tects and reinforces the film. While the other inert-linseed oil films disinte grate within a year when exposed to weatlier, the nnca paint film maintains its intrgrity for several years Although explanations fiave hern given [or a few of the specific weather ing characteristics of these vanous single pigment paint films, it seems de sirable that some further reasons for their weathering characteristics be presented before we consider the formulation of multiple pigment paints The lead and fine oxide pigments are chemically active, that is they leact with organic acids in the vehicle or funned in the film during exposure to produce soaps Thus there is a direct chemical fiond between some of the pigment particles and the organic hinder The soaps lend to form on the surface of the pigment particles which may result in a gradual transition in the film from pigment particle to soap to organic hinder Both lead and zinc soaps are burr shaped, thus providing a further reinforcing effect The chemical bond between pigment particles and the organic binder tends to produce strong films. The lead soaps are softer and more plastic than the vine soaps It is the ultra-violet rays tn the sunlight that are most destruc tive of an organic film Zinc oxide is oparpie to ultra-violet light and thus shields the binder from these destructive rays The basic white lead pig ments are transparent to the ultra-violet light and permit the progressive oxidation and disintegration of the film hy these rays It is the combination of these and other factors that impart to white lead films and to the zinc oxide films their weathering characteristics 7.me sulfide does not react chemically with organic acids to form soaps, hut it is organophilic in nature The zinc sulfide pigment particles in a paint film are well wetted by the organic lunrirr While the sirnng chemical bond that exists in the rase of zinc oxide is absent, stii! the oleophilic nature of die pigment imparts a degree of strength to the film 'I he pigment does not 8 possess a high degree of opacity to ultra-violet light ray vent the progressive disintegration of the film Titanium dioxides do not react chemically with the vehicle to form soaps They also are hydrophilic rather th rutile titanium dioxide is definitely more oleophilic than anatase pigment is not opaque to ultra-violet light while possesses a fairly high degree of opacity. These propertie chalking and disintegration of the anatase titanium dio the greater durability of the rutile film. In general, the extender pigments are chemically in in nature and so tend to produce weak films Fibrous and water-ground mica IKrause of the relatively large siz their particles provide reinforcing properties In the case ments, some calcium soaps may be formed by reaction w ents of the vehicle Then the particle size of the precipi and nodular These facts may explain the poorer weathe ol their films Also, the inerts account-for the difference tween the straight zinc sulfide and titanium dioxide film composite pigments. ' The weathering characteristics of paints composed ations of these white opaque and extender pigments cou similar manner. It would be found that their weathering resultants of the weathering characteristics of the co Thus, a formulator having a clear knowledge of the wea tics of the individual pigments can select the combina desired weathering characteristics Exterior house paint be extremely simple if there were not many other prop considered. These include ease of paint manufacture, s in the package during storage, and paint and film prop sistency, brushing, leveling, drying, opacity, gloss, color similar to our discussion of weathering, the characte various pigments on each of these properties could be pre beneficial to consider vehicle constituents in a similar m effects of the ratio of the pigment to the hinder on the va ties Because of limited space, it is better that we move a ent day paint formulation. I will try to call attention to v vehicle properties as they arise during the discussion. Perhaps the first consideration to the paint formulat lead and zinc oxide were the only available white pigm dollars paid a painter for a day's labor and anything less paint was heresy Sufficient lead and zinc could be pu provide ample hiding with three coats But today, when is general practice and even one coat painting is being pro receive as much hy the hour as their grandfathers did hy obtained with lead and zinc must he reinforced with high such as the titanium and zinc sulfide Usually the desire by the inclusion of from 1 to 1-1/3 pounds titanium diox pounds of ZnS) in a gallon of the paint Rased on the pe pigment, this is usually about 15 per cent titanium dio 9 Irained for best whiteness anil rk'ansmg atiatase grade [ties, this should be the Starting with this I to 1-1/3 pounds anatase titanium dioxide, let us go ahead and formulate an exterior whitr house paint Our single pigment ex(Kisnrc tests tell us that an anatase titanium dioxide paint film is weak, chalks very rapidly and is susceptible to mildew, also that zinc oxide and leaded 7mc oxide films are strong, resist chalking and are fungistatic They, therelore, are logical pigments to use with anatase titanium dioxide Experience has shown that 2% to 3 pounds lead-lree zinc oxide or 3'A to 4'A pounds leaded zinc oxide should be used with 1 to 1-1/3 pounds anatase titanium dioxide On a percentage basis, the 15 per cent titanium dioxide tn the pig ment requires about 30 per cent lead-free or 47 per cent leaded zinc oxide We are now on the road toward balanced weathering, that is controlled erosion and cleansing properties The weathering of the film can he further modified through the addition of white lead pigments. White lead is usually used more because of paint projierties other than the weathering of the film. It is believed to beneficially affect paint mixing and grinding, paint applica tion and flow, paint drying under adverse application or exposure conditions and to aid adherence of the film to the wood surface The quantity used varies from none to three or four pounds in the gallon of paint or 0 to 30 per cent of the pigment. This pigment composition of the white paint now is: Anauis Titanium Dioxide Zinc Oxide White Lead Poundt ] to 1-1/3 255 to 3 0 to 3 or 4 Ptr cent 15 30 0 to 30 This combination contains a high proportion of active pigments and on wratliering may become too strong a film It might under abrupt changes in stress-strain conditions, such as may be caused by the sudden freezing of a water-saturated film, develop cracks or lose adherence to the wood surface. As our tests have shown us inert extender pigments produce weak films. Through the inclusion of inert pigments, the film can be weakened in a very desirable manner The particles of extender pigment distributed throughout the film provide many points or foci where strains developed in the film may lie released by microscopic ruptures between the binder and the inert par ticles instead of by large cracks in the film. As previously stated, the most effective inert extender pigment is water ground mica. This inert besides providing the multiple foci for release of strains reinforces the film Usually five ounces to a pound or three to ten per cent of the pigment is sufficient. The cost of water-ground mica, and its dust ing and poor paint-making properties have retarded its adoption by the paint formulator The other siliceous white extender pigments, which provide some of the lienefits obtained from water-ground mica, are usually selected. Among these fibrous magnesium silicate is rated highest. Experience indi cates that H to V/i pounds or 10 to 20 per cent of the pigment is required although more may be beneficially added 10 The composition of the pigment porliun of our white Anatase Titanium Dioxide Zinc Oxide White Dead (BSWL or BCWL) Fibrous Magnesium Silicate Pnmdt 1 to IV, 2V< to 3 0 in 3 or 4 J/< to IV, We now have indicated 4 to 9-5/6 pounds or 60 to 9 composition of the pigment of our white house paint We a pigment since the content in white house paint will vary fro to eleven pounds, and then we must account for 100 per cen This is best accomplished by increasing the content of in ment. In the case of the formula containing no lead rath magnesium silicate to make up the pigment deficiency, it increase the zinc oxide content by approximately ten per cen per cent mica. Also, in any of the formulas, should extra desired, extra anatase titanium dioxide should lie added wi increase the zinc oxide content by approximately ten per cen white house paint is: Anatase Titanium Dioxide Zinc Oxide BCWL and/or BSWL White extender Pigment* Fvundi 1 to I1/, 2Vn to 3l/ 0 to 3 or 4 1 */j to 4 You will note that we actually have three types of pigm Anatase Titanium Dioxide Lead-free Zinc Oxide Leaded (35541 Zinc Oxide White Lead Inert Extender Pigments / percent 15 40 45 ft percent IS 47 3$ While No. III is perhaps more representative ol the major commercial paints, there is a definite trend toward No. II a I (futneprool paint). The paint formulator has considerable leeway withi modify these basic pigment formulations to meet his spec lowering the quality of the paint. He may raise the titan opacity, increase the zinc oxide to improve mildew resis ground mica for greater weather resistance, etc. We could consider the pigment composition of tinted p manner, but it will not be necessary. In a white tint base anatase titanium dioxide, a rutile titanium dioxide or a zin will be used, because ol the superior tint retention they im film. Since the tinting pigments usually impart appreciable of the opaque white pigment is not required. Also, because ing tendencies of the zinc sulfide and the rutile titanium p greater protection they and the tinting materials provide heavy chalk and too rapid erosion is not encountered. Goo be prepared using only white lead and zinc oxide as the o ments. Formulations similar to those shown for white II rutile titanium dioxide replaces the analasr are frequenlly used, although the titanium content is usually reduced Also, a mic sulfide pigment formula such as the following has found considerable favor as a white tint base: Llthopone Zinc Oxide Mira and/or Magnesium Silicate Per Cent SO to 60 SO to 40 10 to 20 In the pigment composition of his white tint base, the paint formulator lias even more leeway than in hts white in the selection and proportioning of his pigments There has been some tendency to use a titanium-calcium composite pigment for the white opaque pigment both in the tint base and white paint. While this pigment has an advantage over combinations of titanium dioxide and siliceous inerts in the gloss imparted to the film, it is at a disadvantage in dirt retention, mildew resistance, and the weathering of the film Pigmentations containing titanium dioxide with very high contents of a ground natural chalk are being suggested While they are low cost, there should be a greater tendency to encounter film failures than with those that I have previously presented As stated earlier, there are three factors to consider in formulating paint, that is composition of the pigment, composition of the vehicle, and the ratio of pigment to vehicle 1 n general, house paint vehicles consist of lin seed oil, bodied linseed oil, volatile thinners, and liquid driers The properties of the vehicle depend on those of the constituents and the proportions in which thry arc combined Refinement of the oil to improve its color has no influence on the weathering characteristics of paint prepared with it A nor mal raw linseed oil with an acid number of two to four is entirely satisfactory if best whiteness of the liquid paint is nut a requirement, since the yellow color of the raw oil film is bleached on exposure of the paint film to the sun. If best color in the can is desired, a refined light colored oil is preferable The bodied oil should be a heat bodied oil in which temperature and conditions have keen controlled so that progressive bodying of the paint will not occur because of its reaction with the active pigments Oils possessing viscosities over a wide range are suitable. The viscosity of the bodied oil and the ratios of untreated oil, bodied oil. and volatile thinner in the vehicle are interrelated Optimum combination is dependent on the relative impor tance the formulator places on various paint properties and the quantity and composition of the pigment with which it is to be combined. The film formed by a heat bodied oil is more weather resistant than that formed from an untreated oil. The transformation of a raw linseed oil film to a solid and then the disintegration of the film is caused by oxidation. In the cooking of an oil. the increase in viscosity (or the first stage in film formation) is due to polymerization. The oil when exposed as a film continues to solidify and then disintegrates because of oxidation Rut its disintegration will t* slower than that of the raw oil film because part of the film formation was due to polymerization Thus from the paint durability angle, it would he pre ferable that all the oil in the paint vehicle should lie nne that had been poly merized to a high viscosity. There are olher paint properties that make this undrsirahle First, the pigment in the paint must not settle to a hard 12 mass during prolonged shelf storage. The good wetting properties of bodied oil would promote settling of the p house paint must not offer too great resistance when bring reasonably large brush So the high viscosity oil could onl greatly reduced with a volatile thinner. But the consisten (that is the yield and flow properties) must be adjusted so t of desired thickness is applied to a rough surface it will fill t without the contour of the irregularities being reproduced surface of the film. Also, there should be sufficient flow in t the deep brush marks will level out without there being a t paint to sag These properties are best obtained when the both untreated and bodied oil The proportion of bodied oil w viscosity. It may be from perhaps 15 per cent to 50 per cen the viscosity from "Z-6" to "X " The higher the percentage the viscosity of the bodied oil, the higher must be the perce thinner in the vehicle. While a bodied oil of Z-5 or Z-fi and tent of only two-thirds of the vehicle was used in the oil-con made during the war, in the post-war paints there is a trend oil content to provide a thicker nonvolatile paint film Vario can he used and equally excellent durability can be obtained sentative combination is one part bodied oil of Z-2 to Z-3 v parts raw linseed oil, with the total oil in the vehicle 72 to 7 This discussion has been restricted to linseed oil. Man bein considered as partial replacement for linseed oil. 1 w to discuss this phase of the subject, but will say that there to believe that such substitution can be made. Our own l great deal of evidence that replacement of the bodied linse bodied oils can lie made with no deleterious effect on a properties. Either turpentine or a petroleum spirit may be used to consistency and application characteristics. While variou of the soluble soaps of the drying metals lead, manganese, c calcium are used, a combination of lead and manganese naph erally favored. A suitable combination is approximately 0.5 0.015 per cent Mn, based on the total oil content in the vehicl We have discussed the composition of the pigment and of the vehicle; all that remains to complete our paints is to de portions of the two. The ideas on this are quite diversi studies were made several years ago covering the Icad-zinc barium pigmcnt-lead-zinc-inert, and iitbopone-zinc oxide-in in which a representative composition of the vehicle was 80 refined linseed oil, 8 per cent bodied linseed oil (Q viscosity) volatile thinner and drier These studies indicated that there limited range for the pigment volume content of the nonv optimum paint durability This range was generally accepte 30 per cent pigment volume During the war when the no was changed to a combination of very heavy bodied oil and volatile content increased to over 30 per cent, it was neces the pigment content 10 ohtain paints of application consistenc 13 i varied in pigment volume but averaged about .15 per cent In the present dajr depend on white lead lor reactivity and soap formation and va paints that 1 have outlined, in which the oil content ol the vehicle is 72 to 76 hardening effect. They also take advantage of the good durabi per cent, the pigment volume in the nonvolatile film of paints of brushing opacity of rutile titanium dioxide or the excellent buffering p I consistency generally falls between 50 and .15 per cent Studies that have Cryptone MS (zinc sulfide-magnesium silicate pigment). To been made indicate that the pigment volume ol present day paints may be tional opacity and film thickness, they tend to use higher pigm varied appreciably without changing the durability of the paint and that the than in finish coat paint. There are two types of pigmentatio 30 to 35 per cent is within the optimum range In fact, exposure results indi cate that if the pigment-vehicle ratio is selected to produce correct paint favor, (a) titanium, lead, and inerts, and (b) Ciyptone MS zinc oxide. The vehicle generally contains more, but a lower vis application consistency, both the paint durability and the pigment volume oil than used in regular house paint, and the zinc oxide-free will fall within the optimum range Therefore, our paints will be made to cor usually contain some resin varnish. Aluminum powder prime rect application consistency with the assurance that optimum durability will been promoted. While their resistance to water is good, they ha j be obtained from the specific pigment and vehicle combinations. Before leav vantage of frequently causing alligatoring of the finish coat an ing this subject, I wish to mention that one organization has recently prom are gray they require two coats of the white finish paint. ulgated the idea that oil requirements of the pigment are the controlling While the special primer two-coat system possessed adv factor. They propose that the magnesium silicate in the pigmentation be re placed on an equivalent oil requirement basis by a ground natural whiting. Since the oil requirement of the whiting is much lower than that of the mag nesium silicate much more is used and thus the total pigment volume in the two coats of the prewar raw linseed oil type paints, its advanta coats of today's house paint is questionable. Since present day pa pared with a similar type of bodied oil vehicle, as a priming coat many of the properties of the special primers. They posse dry film increased several per cent Further data are needed, more to deter mine (he merits of the ground natural whiting as an inert than the sound penetration and dry with sufficiently low gloss to provide good the second coat. The paint can be packaged at a consistency su ness of the oil requirement theory. coat application without any additions being made by the paint The paint manufacturer has learned that although he produces an ex paint manufacturer is assured of the composition of the paint fi cellent paint, the results obtained with it may be far from excellent. Ad ditions made by the painter, poor application, painting under unsuitable the advantage that the painter will make no error and apply a lated only for the primer coat as a finish coat. conditions of weather or temperature, improper preparation or an unsatis As in the case of the various pigment compositions for factory surface, or abnormal exposure conditions may result in premature excellent results can be obtained with or without the use of a sp failure of the best paint. Paint manufacturers in their endeavor to over It is this fact, that desired results can be obtained in various wa come these difficulties print directions, on the labels of the paint container mits the paint technician to use his knowledge and ingenuity in But experience has prove'd that frequently the user does not read the direc his paints and that provides the healthy competition that e tions, and if he does, may not follow them industry. j In a further attempt to overcome some of the failures due to improper reduction of the finish coat paint for the priming coat to poor preparation of the surface to be painted and to the use of woods that present a paint adherence problem, special priming paints were formulated There is no question that better results were obtained with these special primers than when the prewar raw linseed oil type house paint was used for the priming coat These priming paints were the first to lie formulated with an appreci able percentage of bodied Oil in the vehicle In fact, the composition of the vehicle does not differ greatly from that used in present day regular house paints, except that some of the primer vehicles contain a small percentage of varnish Since the primer serves a different purpose than the finish paint, its requirements are somewhat different The primer paint film should possess good adherence to the wood, maintain distensibility, and not be detrimentally affectrd by moisture It should lie compatible with the finish coat and dry with low sheen so that it promotes neither separation nor failure of the finish coat film Since it is not exposed to the atmosphere, it does not need the high resistance to mildew and dirt nor the good maintenance of whiteness and tint that are so iiiqxirtaiit in the finish coat paint For this reason, main forinulators use little zinc oxide in their sjwcial primer but 14 IS 00 0007-SWP-000127257 The New Jersey Zinc Company 160 Front Street New York 7, N. Y. ^73^ 0007-SWP-000127258