Document e5roz1KkXGZM1b404dKjpMa4q

^rational <>rinitifir rr11mt "Cst* A CA*Zt.0\*C'*Q* ^Mnuslf m 11 It Tart}im* JVssnriaftoit INC O A __P O____ A.___ A T____C O aroi NEW rOK AVE.N.W. WASHINGTON D C. APRIL l6, 1934 TO THE MEMBERS OF THE EXECUTIVE COl'MITTEE. Dear Sirs: In regard to the natter of the chapter on paints in the "^ood Handbook" of the Forest Prod'-icts Laboratory, which, was diseased at the meeting of the Executive Committee in Chicago, I would suggest that.you read the letter which I have prepared on the subject and s^nt to Dr, Browne, Yours very truly, * H. A. Gardner APRIL 16, 1934 Dr, F. L, Browne Forest Products Laboratory Madison, Wisconsin NCA 0 02614 Lear Dr, Browne! I certainly appreciate your icindness in coming over to Chicago Thursday evening to talk with me regarding the painting chapter of the new "Wood Handbook.* The members of our committee were all glad to have the oppor tunity of meeting you at that time, I also want to thank you for letting me take back to Washington the painting chapter so that I could go over it and return to you some suggestions ^iich might be the basis of changes which could . be made before the chapter is sent to the printer, I have therefore marked some of the page? with a circle, at the points where changes might be considered. Page 518, Y9U have indicated that "woodwork is painted usually to improve its appearance,* I think you should also state that paint preserves wood from weathering. Page 519, You state that "paints and varnishes are not effective as . preservatives against decay,* I would suggest that you qualify this by indicating that "Decay" means the form of disintegration caused by wood destroying fungi. N 3908 Page 2 This would, clear the matter up in the minds of pone readers. O You have also' stated on this rage that "shingle stains are often made with relatively volatile distillates which lose their toxic properties rather rapidly." I think you will find that many shingle stains are mde with high toiling creosotes which remain in the film for very long periods of time. Page 523* You suggest that "the oily extract in cypress will.retard the drying of paints which do not contain white lead," I think you will.find certain grades of oily cypress retard the drying of any kind of paint. Doubtless, however, white lead acts to some extent as a drying stimulant. Page 525* You refer to the fading ox' colors.due to chalking. You night indicate that this is not really fading but an optical effect, caused by the chalk which masks the real color of the paint. On the sore page you suggest that "good paints improperly applied might form conspicuous cracks.n I think you night modify this statement. At the bottom of the same page, I think you might modify the state ment regarding the fragments of paint on repainted coatings* Page 530, You state that "paste paints have the important advantage over prepared paints of being easily mixed with any desired proportion of f\ pigment and oil." I think you are in error on this, as it is extremely simple to add oil and thinner to prepared paints in order to get practically any desired proportion or mix. .In other words, prepared paints are usually made of a pretty heavy body so that they are receptive to reduction, and they surely are most easy to mix. You also state on the same page that "paste paints are better adapted than prepared paints to two-coat work on new wood and to one-coat repainting," I do not think this statement confirms with the generally accepted knowledge of the subject. Prepared paints certainly are as well adapted as paste paints to the types of work referred to* I would strongly recommeijd that you reconsider the statements referred to on .this page* Page 531* You refer to straight white lead paint, and then you state * that "all other reliable phite paints contain a mixture of zinc oxide with one or more.other white pigments." There are, of course, some paints that do not contain zinc oxide. S ome are made with mixtures of white lead and tit anium oxide. You also state on th$.s page that "the outstanding merit of pure white lead is that upon weathering it breaks up into fragments smaller than those of paints containing zinc oxide," TThile this statement might have been true of many mix^d paints containing zinc oxide, it certainly is not true of paints containing some of the modern mixtures of white lead, zinc oxide, and titanium . pigments, Those latter mixtures, in my own tests have weathered for many years without.breaking up into large fragments. As a matter of fact, the titan.J ium seems in many cases to overcome,the checking and cracking of the lead and zinc pigments, and it is possible that some of the newly developed p\ire zinc sulfides might have the same effect. Page 532, You state that, "neglected rurfacos of white lead paint can usually be restored to presentable condition with less labor and expense than similar surfaces coated with other white paints," I do not chock on this NCA 0 02615 Page 3 entirely. If white lead has not been properly mixed, and if it alligators heavily, it is difficult to restore. On the other hand, certain mixtures of white lead, zinc oxide,' and other pigments may weather dovm to a chalked surface but not checked surfaces, that are easy to repaint, I believe, there fore, that you might to advantage modify this statement. On the same page you state that "paints containing a moderate amount of zinc oxide take longer than a pure white lead paint to become fissured, retain tints more satisfactorily, and give better protection to the rood against weathering, but if they contain too much zinc oxide the ftssTcs of deterioration are conspicuous, and the fragments of coating that sequently fall off are large. For that reason the zinc oxide should a~.v\nt to no more than }C?e by weight of the total pigment," --- I th'.hs m ge.v*ta\ your presentation of this is very clear and might be somewhat similar that of many other observers. On the other hand, I have scon mary tsards contain ing more zinc oride than which have been satisfactory. As h rr.att-?r of fact, one of the madam paints put out at the present time,contains LVf of zinc oxide and cl'C^ of titanium oxide, ground in a tung oil liquid. Ibis paint has already given interesting results in early tests,, In some cf my own tests during the past four or five years, I have exposed paints with as high as zinc oxide, with fairly interesting results, but,,of coa"?e, I believe that quantity .is entirely too high, ITcvertheless, the trend in zinc oxide paints is towards the xxse of a very coarse zinc oxide. Paints made with the coarse oxides seem to weather very satisfactorily as compared to paints made with the v^ry finely divided zinc oxides. It is possible, therefore, that in the future, we may see developments in this direction, which will be worth while. ' . On the same page you refer to various compositions for mixed paints, and I think your statement might to advantage be modified along the following lines. You might, for instance, state as follows: "It is probably unwise to enter into a dis* cussion as to what constitutes the best paint, but it nay be stated that insofar as high grade exterior paints are concerned, those put out in this country usually contain from SO to 100 percent of lead and zinc, or of lead, zinc and titanium pigments, when furnished in white; and reinforced with colors that add to the durability of the paint, when they are furnished in tints. Zinc sulfide is another pigment which has recently come into . use in compositions of this character. Antimony oxide is an additional.pigment which has been employed in prepared paints, and it has characteristics somewhat similar to those of white le^d." Page 533* Tou state that Hhe deeply colorod paints are usually much more durable and often cheaper than white or light colored paints." This may in some instances be true. I prcs'Trae you r^fer to iron oxide paints* On the other hand, there are,certain colored paints, such as pure chrome ypllow paints or specially bright reds, which are very much more expensive than white or light tinted paints. You might, therefore, modify this statement# Page 53U, You state that "in general the best paint of a chosen color is the one containing the least proportion of in?rt pigments" etc# This statement might bo'modified, as certain greens containing inert my be more durable than the C. P. greens, in certain liquids#  Page 4 On the same page.you state that "ordinarily stains are chc-aper and more durable than paints*" I think you will^find that stains are generally less durable than paints# Moreover# your recommendation regarding the oil content of.stains might be modified, as the amount of oil you have recommended might produce a glossy surface which would not be desirable 'under certain conditions# Page 536# There is.a little question in my mind as to your statement to the effect that "over old coatings that are fissured sprayed paint may not prove so durable as.brushed paint#" You might lock into this a bit# Possibly the thicker coating produced by spraying would make an even more durable film on some surfaces. Page 537# On this page you have presented a rather extensive chart showing the reductions for the first, second and third coats for paste paints that are to be used for painting new wood surfaces, and on page 5^0 you have, presented a similar chart for paste paints that are to be used for repainting old surfaces. It seems to me that these charts might be eliminated entirely, as they might be entirely incorrect 9or different kinds of paste paints# While the recommendations might be satisfactory for pure lead and,oil, it is.not stated whether the lead and oil is of the old type, namely, 90 lead and 10 of linseed oil, or of the new type which contains very much more oil. Moreover, there are many other paste paints on the market, which the consumer might pur chase, and these mixed pigment paste paints might require entirely different reductions than straight white lead. Would it not be proper to eliminate these charts and merely state that the purchaser will find praper reduction directions on the label of the paste paint which he buys, and that he should follow as closely as possible the reductions recommended by the manufacturer? Page 538# Your suggestion that three coats of prepared paint should always be applied to new wood would, in my opinion{apply also to white lead and to other paste paints, I doubt if a satisfactory job on any new surface will result with only two coats of paint# On the same page you suggest that paint is more durable on certain kinds of refractory,woods, if the wood is primed with aluminum paint# It might be well to modify this to state that certain types of special primers are also desirable on such woods. In other words, there are special primers on the market, other than aluminum, idiich might be used with the same good results that are obtained with aluminum# Page 539. You suggest that repainting should be done when fissures ap pear in the coating, and should never be deferred beyond the earliest begin ning of flaking# Possibly you could wo^k in the fact that repainting often should be done when the surface gets dull and chalky and before it gets to the point of failure by checking or flaking# At the bottom of the same page you will find it might be well to bring in niy previous criticism regarding the use of the manufacturer* s. directions for reducing all kinds of paetes, semi-pastes, and ready mixed paints, rather than to use the special tables of reductions which you have presented. On page 5^6 you present some photographs which indicate the superiority of aluminum paint as a primer for certain kinds of wood, I am wondering if you have any other photographs you could present, indicating the good results that are obtained on the same kinds of refractory woods with the other special NC A 0 02617 primers available on the market. Moreover, there is another photograph of four panels, indicating in your tests very much better results with white lead than with some special mixed paints, I am wondering if these are represen tative of your final conclusions, as the result of all of your tests. For instance, some of the photographs do not appear to check at all with the experi ence I have had with some of these mixtures. Page 5Ug presents a rather elaborate table shoving the greater mois ture excluding effectiveness of aluminum paints. There is a question in my mind, of course, as to what this means from the standpoint of the primer on certain kinds of wood. It might be desirable to boil this table down to a brief statement, as the average consumer would not be able to understand all the technical terms used therein, Fossibly a generalization would be worth while, Page 55* You suggest that when architectural design calls for a weather-beaten appearance on a wood surface, the wood should be allowed to weather naturally, "especially since uncoated exterior woodwork is not necessarily lacking in durability," I think you might modify this statement, as uncoated dwellings would soon show warping, cupping and distinct signs of weathering that would not bo especially attractive. On the same page you suggest the greater life of interior finishes, I think you can modify this to state that interior finishes have good life inside, but they.do not wear outside as long as exterior paints. Page 552* In your suggestion that intorior surfaces might be painted with the same materials as used for outside surfaces, it would be well to remember that exterior paints are usually off-color as compared to the modern types of flat and gloss enamels used for interior work. The pigments used, for the interior paints, are, of course, very much whiter and of clearer tone. In the same paragraph you refer to enamels being less opaque than paints, As a matter of fact, modern enamels made with titanium oxide and zinc sulfide may in some instances be very much more opaque than exterior paints. Page 553, You suggest priming inside surfaces with white lead. You might also suggest the use of special enamel undercoaters which are available for this purpose, Page 55U, In speaking of stains for interior surfaces, you mi^it refer to the newly developed stains which contain solvents which do not raise the grain of wood. Page 555, Your reference to the superiority of shellac over certain varnishes for sealing properties might be modified. Page 556, Dull surfaces may be produced with ready made varnishes and lacquers of $he dull type. Page 557* You mi^bt oodify your statement regarding coatings for floors that carry heavy traffic* I hope you will not think tbat I have been too critical of your article, I ant quite sure that the new "Wood Handbook*, idien it appears, will, be of tremendous value to the general public, and I sincerely trust that the chapter on paints will be modified so that it will be of the greatest service, HAfi-P Yours very truly, NCA S!gncd) H A, Gardner 0 02618 ji>ri fliitftr rrtt mt MCNftr A ZA*OHt*.Oi*tCTO* ^Catuuuil `pauii unit ?arquer JU' s?uctaHiut INC O N_P____ O_____ A T _C___________O aaoi NCW VCRK AVE..N. W. WASHINGTON. O C. April 24, 1934. To the members of the Executive Committee. Dear Sirs: Dr. Browne's Wood Handbook Dr. Browne wrote me under date of April 20th in the form of an eight page letter, a copy of which you will find herewith. The last paragraph of his letter appears to sum up his attitude. Please note my reply to Dr. Browne, dated April 24th. Yours very truly. H. A. Gardner HAG-P NCA 0 02619 N 3908.01 BOUJilTlFlC .SS'JTIOU NATIONAL PAINT, . VARNISH AND LA.O$.JPR ASSOCIATION " ... . "'ashingbon, D. C . -.Id* .3 934. Dr. F. L. Browne /A. Forest Products Laboratory, i;'. Yadison, xilis. '- - " Dear Dr/ Browne: I want to thank yon f<n your oo y-i'ciions ive letter of April 80th. You have gone to n lot of t'-nublo to ansv.or ny suggestions, but I really think you have failed to group the significance of this me M ^r . A penpalet :-uch ns you pmoose, if issued under author 1 by of tnc U. S. Government would carry tremendous weight with the users of paint. Un fortunately, however, the results of the panel tests which mu have mode in different ports of the cmml. ry do not in dgned both paste and ready mi/.td compos have given satisfactory service on the majority of largo painting job3 that '.vere in condition to receive paint. It is conceivable, therefore, that entirely erroneous results 'light be obtained from snail size test panels such as you hove used and such as our own laboratory has employed m / >! WXBa r Y ^1 _ ....... N 3908.02 V- `."/VirV! * \ - ' ! j, v. 4' \ - I ( ) .:hope*-you wi 11 receive .the above,.suggestions . in the fi'i^ndly. v/ay.. that they are made, and tliai my com-y. ments.vvill^not-'in any way disturb the friendly relationsc~ which have^always existed between the Forest Products Laboratory-and .our own. 1 With best wishes,J-: i . C. 1 -V . Yours very truly, e ^ .. .V'.*'* ' ~ *,** \ (Signed) H. A. Gardner hag-p'7' ) k *1 1 BEST w PY U. o. ARTIST CF ADRiOULTDRE Forest Service kadi son, 'Vi scons in April 20, 1354 _<r. a. .-a raner 2201 Few York Ave., N. 77. `7e s h i n g ten, D. 0. Dear Dr. Gardner: Thank you for the comments in your Tetter of Aar 16 with which --you "re"tu--r-n--e- Jd the chapter on painting for our Food Handbook, I enclose conies of sene further corresoor.- ;-nce 'ion kr Kohr that I should like you to read before going on with he discussion of your specific criticisms that fellows: rase :18: The behavior of woodwork on veatnermg is Qi ?ea eise:. Here in the Handbook and is a S 3C -- tion on uncoated exterior woodwork on.page 551 of this chant er. Since the objection to weathering is usually a matte r of appearance primarily I feel that the statemeaint cover s the ground satisfactorily as it is. To alter r you s uggest would involve a serious reorganization of tl n e chant er that would be less desirable from the point of view of ar chitects and engineers. P_ase 519: The meaning of "decay" in this sentence is clearly deiihed'by inference. The Handbook contains two whole chapters on decay and wood preservation. Some of our critics feel that the matter will be all too clear to read ers as it is. iiy knowledge of the composition of shingle stains is mostly second-hand. Your criticism comes as a surprise in view of the advice I have received from others. Perhaps specific discussion of distillation ranges would bring a closer understanding but time does not permit that at present. I think the situation can be met by changing "generally" to "sometimes" because I am sure tnat many stains contain creosotes that we consider relatively volatile. Page 523: There is no doubt that white lead markedly stimulates the drying of paint on oily cypress. . '<7e have examined this question rather thoroughly ana ooteined samples of exceedingly oily cypress for tne purpose. *hite lead paint never failed to ary reasonably promptly on any of them and always much faster than lead-free paints which on white pinfe dried fully as rapidly as^the wmte lead paint. I think that the facts are expressed by tne present reading as fully as is necessary and that further elabora tion would give the subject undue importance. N C A 0 02622 N 3908.03 NC A 0 02623 G-. rs.ge 2 eeas ag?e< 625: Explanation of the mechanism of unduly tecnnical for this purpose. Architects fad and r-5 r.gineers are concerned only with fact of change in color, he mechanics inrerests oaint technologists but their are not moor' Tor this publication, Yo u do not indicate no?/ you suggest modifying t :.nt th 2 ft H"good paints improperly applied nay form cm soic ucus craens." *1 have in mind Judge P.osenberry' s n d is.cn, painted with white lead, another house -- fi all 1 1C * ? o r. ted with a good prepared paint, and practical the im hood es fr buildings 0:u n nsas Cailt-o-y----n--- gto the Los Rock Island-Southern Fac Angeles, painted with fY colo red rain ts. Rueettaaiilead eliabooration orf the conditions i?rd ' p~ to S'uch conspicuous cracking seems unnecessary in view of the specific*directions given in the chapter for us he pa ints properly. I do not understand what modification you wish forthe statement about fragments of paint on repainted coatings. Page 527: A circle is drawn, but no comment given about a paragraph that reads: :!?iny resins consist of a solid rosin and*a volatile liouid such as turpentine. They affect paint unfavorably in tv/o ways, (1) by reacting chem ically with certain paint pigments, notably zinc oxide, forming sosps that tend to make coatings more brittle, etc." As to the fact that the pines definitely discriminate against paints containing zinc oxide our evidence is so abundant end consistent ever since we began our work that it must be accepted,. The explanation offered is in' accord with prevail ing ideas about metallic soaps in oaint and therefore seems justified. I think it more nelpful in this case to give the explanation than to let the statement of fact ride without it. Page 528: A circle is drawn opposite Table 57, wnich gives our classification of softwoods for painting but I find no comment in your letter. Page 530: A number of well informed paint men hold that the finai coat of paint should have 28 to oO percent pigment volume. A number of second grade prepared paints, particularly lithopone paints, are sold with 28 percent pig ment volume and Sears Roebuck's "Longlife" paint has mater ially higher pigment volume but I do not know any first grade prepared paint that passes 28 percent pigment volume and very few that approach it. In other words, most prepared paints of good Quality are already overloaded with linseed oil. If the paint settles reasonably well it is, of course, possible to pour off some of the oil but I have never seen that practice recommended. It certainly is usually undesir able to add oil to the finish-coat of prepared paint and in that case the second-coat oaint must be mixed with as low a pigment volume as the final coat. To the best of my knowledge all sellers of paste paint recommend a second-coat mixture of materially higher pigment volume than the third-coat mixture. All of our crait-smen's knowledge as well as theoretical Dr. H. A. D. rage 3 consideration point to the desirability of a very high pig r\ ment volume for second-coat paint. The desirable relations in pigment volume are easily obtained with paste saints out they cannot be obtained witn such prepared saints* as Sher.vin- 'Villiams, Love Bros., Du rent's ana Pittsburgh's unless part of the vehicle is poured off and replaced with volatile in mixing the second coat-. apslies to the use of caste and precared paints for tec-coat initial painting and br.e-ccai repainting. The mixtures of caste saint that I recommend for these surocses cannot be marched with rescect to pigment volume and* spreading rate wi th any high grade*prepared sain os v/ith which I am xamil iar and without these*necessary conditions of pigment volume and spreading rare I have been unab 1 e to make* any t;vc-ccat initial paint job compare favorably in serviceableness with a three-coat joe. I consider these matters of very great importance .\*ext to moisture failures of paints the most common* causes 01 unsat isfac tory "0c. 1 nt service in my cpini on are the over-____r ____ l. _________ ______________J * _ J- _______ -_ _ *_____ _______ ____ ___ ' 1. _ _________ -- i ca ding of P2 int w i th 1 inseed ci 1 and abpli cation of too / Tm--t fjU-oviiCr** tie p any* se or aint. paint actic The manu i.acc': es ana i >* vxnj etitive s ituati turer to aavise h or that rea son we oh* ma is cu are kes it dif f i cult stoners ag's ins t particular ly obi 1 ,~R.Z 3 d to make pur 3 6 Ives clea r about it. I think that i 7VOU id be a gr eat m 1ST a k e for pre pared paint nanuiacturers to r ecom mena their pa in ts for tv; c-coat init ial painting and cne-ccat repaintinm. Page 531: I know that experiments have beenjnade with mixtures oi wnite lead and titanium pigments but I do not know of any linseed oil house paints of that formula that have been sold long enougn to ~5e recommended as reliable house paints. It is my understanding that special vehicles are considered necessary with such pigment mixtures. If I am wrong I should like very much to have the names of any that bear formula labels and to see tests or houses that show them in their final form of disintegration. I have long been very enthusiastic about paints containing titanium pigments, white lead, and zinc oxide. It has been my experience that they do take longer to become fissured and to start flaking than lead and zinc paints.but I have yet to see one that does not ultimately reach this condition. If there were such a formula our present effort to modify linseed oil to prevent embrittlement and obtain equal serviceableness on southern pine and redwood would be quite unnecessary. Zinc sulfide, nowever, is quite unlike titanium dioxide because it is definitely a checking pigpent like white lead. ,1 have rarely found typical paint checking in a white paint that did not contain either wnite lead or zinc sulfide. In other words checking seems to be a property imparted by hydrophobic pigments. N C A 0 02624 Dr. H. A. N C A 0 02625 Fags 4 Page 532: I think that you overlook the care fully emphasized adjective ''neglected". Lead and zinc saints that are chalking but have not.yet reached the staze of flaking a-se not yet neglected. If repainted at this ti:::e they can be repainted with one coat more easily than coatings of white lead of the sane age but if flaking is once allowed to go very far the conditions become very different, particularly if such neglect is practiced after, each of several recainrincs. me limit of 30 percent ior zinc oxiae is oi cc ry and cased on Federal Specification _T3_r ine u th>' v -- * * 30'w' percV e-- *n tV _z--iVn4 Wc Wox-- iVdi We*wtwo r 'w- hic*h* yyou re We^r is - r.W: V a 11 ii : eea oil paint end is not yet old enough to enter int this cmiscussion. VThile I am aware of the evidence that ccar se zinc oxides can be used sore generously than une 0 inc cx ides that fact cannot alter a recommendation of this kind un til either the kind of zinc oxide becomes part of 1 he for mula label or the coarser types of zinc oxide dis- plac the s~O t. aoD' enerdllv the tc-ment should tvoes now in use. be made general I do enough not think that to admit S3 per cent 2 1 ne oxide and 1 percent white lead as a satisfactory pi i- - o-'1 ent for linseed oil paint. Prise 533: The fact that chrome.yellow and bright red paints'~ar'e as expensive or sore expensive than white paints is specifically stated on this page. Page 534: In view of the limitation of the dis cussion to-Tinseea oil house oaints, conflicting advice from other sources, and the comparatively minor importance of your point with reference to reduced greens in certain liq uids I do not believe that further elaboration is advisable. My own work with stains has been very limited but I have been observing the practice of houseowners with both stained and painted woodwork, I note that, as a rule, the trim is repainted two or three times to every time .the shingles or siding is stained. I have no standard of dura bility for stains as I have for paints and it may be main tained that houseowners habitually neglect staining more than they do painting but until a standard of duraoility for staining is set up I think that it is inadvisable to make such distinctions. My statement about the proportions of oil in good stains is taken from the national Lead Company, whose advice on the subject seems to me the most rational I have seen. 'Pase 536: Tie h?zve a barn in Madison on which badly fissured old "paint was repainted by a contractor using brush and by a contractor using the spray. The work was very carefully supervised and record kept of the paint con sumed. The results are very definite. Page 537: In my opinion these charts or their . , equivalent are essential. Tnere is no point on which aremtects, engineers, and painters need more vigorous mstruc- N C A 0 02626 Dr. H. A. C*. Fags tion than in the mixing of paint wit h plenty of pigment ;.nd in keening spreading rates within r e asonable bounds, General statements mean nothing. D e finite fi gures must ce given. '.vhile some variation in the volume re lations of mercial naste paints is possible it is very s mall as cc pared, with the*abuse I am trryyimng to correct. The formu las as - en are applicable particularly to soft paste whit e 1a so nd to mixed pigment be obtained if neavv paste baste pain ts but whit e lead C^ IS od results used inst will ead. stated these formulas'can be aopl led more easily L the >:ed pigment pastes, which are sold by vo1urn e, thar the Lte.iead pastes, wr.ich are sold by weight. Unfcrtunately mixing directions are not always ;iven on '. C"*. 'O">wISr Paste white lead for example, does not carry su i hi: ecticns on the label and I note that recent shipments of Dutch oov sort paste co not give even tne composition. Our building just now is the scene of much activity by contracting painters ana I find that the con tainers in which the paints are shipped usually fail to giv; either " cc* mDO's'it'ion* oi m' e pai'rm' * *or' a"irecuJ i'ons i*cr mixi' ng 1_t. ii.ese conditions do not favor good painting practice and I feel sure that re must say sbnethmg definite about the subject if our Handbook is to be useful. I do not cei eve t; sat anyone will go far wrong m using ;hese ulas : `or mixing any soft paste paint. V. a cons pair, tea L'n ciV n'i.u '-a wv***w ww* wwww ^*. ** "^ vw**^.*v_*w nothing else. I have repeatedly tested two-coat painting against three-coat painting during the past 10 years and find that, wh en the necessary conditions for good two-coat paint- ing are met. the results are just about as satisfactory as they are with three-coat jobs. I7e cannot ignore evidence on such a scale. Two-coat painting, however, must be done correct 1 y because there is no extra coat to make up for de ficienci es in priming or stingy application. I do not know how to paint acceptably in two coats with prepared paints. So far I have seen no special priming paint that is comparable with aluminum primer for retarding flaking from sumlerwood on southern pine and Douglas fir. I feel confi dent that, when any of the better known manufacturers has such a primer, his technical staff will want me to try it. So far no maker of such primer has presented it to me for that purpose though they have asked me to test them for resistance to moisture blistering. Such products a.s Wallhide Exterior Primer and Peel-Kill are not, in my opinion, com petitive with aluminum primer at all. Page 539: I would not repaint.my own house when the paint Decones dull and chalky not only because I can't afford to but because it is often dangerous. Too frequent Dr. H. A. G. NCA 0 02627 Fage 6 repainting is dangerous unless the painting procedure has been guided from the beginning with such purpose in view. The common practice of overloading paint with linseed oil especially when the paint contains zinc oxide to protect the oil, makes it necessary to allow the coating to age .veil before repainting it. Failure to do so leads to crack ing and slipping of zmc-containing paints and to allisatcring of 'white* lead. These troubles are quite common among the more affluent houseowners. Pa; 6: rcr reasons aireaay aiscussea jl can . no onotcsrapn oi retarded flaking from summerrood obtained with a special or imer other tnan a rum mum., oome cay i me to be able to do so but the orimer must first be discoveerea, The other illustr at ion was very carefully chosen to illus trace orinciDlo? brought out in the text! On redwood all three zinc-cbntsi ning~paints are fully as satisfactory as the white leaci. On white pine the white lead is as satis factory as it is cn redwood but the zinc-containing oaint show tne antawoni stic effect cf the piny resin in white p :<o o v*ell cn southern nine or Douglas fir as aoes on rearoca. making the iliust rememoered, of co in a photograph i necessary to let tne exposure contu well into the*per iod of oaint neglect. This naturally tends to favor v:h its lead as compared with zinc-ccntainins oeinis because it is in this period that the good feature: of v;hite lead are brought out*. gage . sJ The data on moisture excluding.effective ness are r'eouestea by our correspondents more often than any other on; : subject in our wood finishing activities, Further more this laboratory is practically the only source of such information at present. Omission of the data would justly subject us to very severe criticism. Page 551: The weathering of unpainted exterior woodwork is adeouately described elsewhere in the Handbook and the development oi cupping, twisting, and checking is mentioned in tne very next sentence. Tne problem is one about which we are frequently consulted and cannot T/ell be avoided. Since the oldest frame house in America remains to this day unpainted I think that the statement is entirely reasonable. I do not understand why any reader should suppose that an interior finish could be used satisfactorily out doors. Introduction of unnecessary statements tends to r,e confusing rather than helpful. Paste 552: I shall suggest insertion of "better color" among tne superiorities or interior enamels over exterior paints. liy sentence about the relative opacity of paints and enamels is qualified by "usually". The high opacity Dr. H. A. O'# Page area r ever .. as it stands-. Page 553: As I understand it, enamel undercoate are not primers and should be applied after the Oil:: f .-age : / . me ne intermediate in character between water stains ana on stains, both in respect to the appearance produced and to grain raising, bring them in requires another fairly long'sentence .-hi.: does~not seem to "0,5 justified from tne point of vies,- of their importance in architectural finisning. is not clear to me ho?; you mould fish the statement about varnish and shellac as ea i to be modified. ?.ge_ ')0O\ The comment is not clear to me s 1 r.c C Cv -meni i.grees with the statement in your letter. na _r._-._u_c__ :57: Once more I am uncertain as to the bind of modification 01 my statement that yon suggest. Nearly all of the suggestions made deal with is.-u: about v hi oil I have thought a great deal for many years end have been reasonably familiar with the varied points of view of many persons. Since I had them clearly in mind while writing* this chanter I find myself unable to make man.} serious alterations. I feel keenly that you,do not fully appreciate the extent to which I have to deal with competent criticisms that run directly counter to your own, which makes it necessary for me to rely primarily upon evidence that I have been able to get directly and lo oe very cautious in allowing the opinions of others to influence my judgment. To one in my position it becomes evident that each industry tends to build up for itself a body of sincere opinion supposedly based upon sound experience but resulting in fact from "wishful thinking." I nope that my inability to accept some of the opinions that have long gone unchallenged in the mixed paint industry will not be considered a discourtesy but will instead lead the industry to a serious effort to re examine its position and subject some of the postulates it has long accepted to practical test. Very truly yours, (Signed) F. L. Browne . Senior Chemist N C A 0 02628