Document oDROn2xdojymNpz1DkkkQG7O3

ALLIED RESEARCH LABORATORIES Report of Investigations for February, 1944 M. VAN LOO 7/177 - Pigment Studies An extensive program for the evaluation of the brightness and opa city of the various white pigments is under way* While the observations re corded are still too limited to permit setting up opacities for specific pigments, the general plan is submitted for comments and suggestions* We hope that when this v/ork is concluded an index system will be established with which the fonsulator may blend opaque pigments accurately with extenders to obtain any desired opacity level in the finished paint. It is anticipated that the various pigments will behave differently in formu lations of different types, depending on the proportion and kind of binder, pigment packing, etc. gated: For the current wcok, fov.r types of formulations will be investi 1. Exterior oil type house paints* 2. Interior "varnish type" flat wall paints. 3* Interior water emulsion flat paints. 4. Interior high gloss enamels* A suitable range of pigment-volume-concentrations will be covered : in each group. For the first analysis we intend to prepare separate index ? systems for each paint type being studied. The technique will be patterned after that employed by the Hew York Production Club as reported in "Paint, Oil, and Chemical Review," November 18, 1943, "A Critical Survey of Methods of Measuring Dry Hiding Power of Paints," The test method consists of (1) the application of the paints by the draw-down method over a black-white contrast, (2) the calculation of the spreading rate by .the wet/dry factor method, (3) a determination of contrast ratio end brightness by photo-electric measurement, and (4) plotting the con trast ratios versus spreading rates or film thicknesses so that the opacities may ultimately be expressed in square feet per pound at a given degree of hiding. N14194 97 - S7P 471 " 7-SWP-000018747 Further work on Gloucester Ti02 2233 M confirms previous findings that it is not suitable for use in white top coats, even as a part of the Ti02 used. Panels 7976-7 were prepared for exposure at Chicago south and north, end Florida south, to compare SWP Gloss TJhite with Dehydrol replacing (48), as described in the last report. Panels 7978-84 were prepared for exposure at Chicago and Florida to 2- M.. VAN LOO Cont. W* &' ^97 - Pont. ly"..- fc: f'V. % 68.2& Leaded Zinc 18.25 Lithopone 9.1$ Mica 4.5$ Magnesium Silicate This formula would lack brightness, hiding would still be low, ?>{, - the film would accumulate dirt, which probably would shed unevenly, and the film would check. !F&*i... A low Ti02 pigmentation was also included, vdth:. 71.255 Leaded Zinc 20.7$ Titanium Magnesium 8.1$ Mica S5;` 3?>' Panels were prepared in both white and tints, using both R 200 and &v R 610 Ti03 in the low Ti03 paints. Panels 7985-91 were prepared for exposure using the CW 1581 -- Mineralite extender replacement (5$ and 7$) for 20 L in S7JP doss TVhite,. as discussed in the January report. fftf.'-; iv;.- Exposure panels 7992-4 were prepared for Chicago and Florida cover ing a temporary formula for STtP tints to conserve 2174 dry, R 610, through the use of lead titanate, which was available for limited, production.. The basic tint formula of 2-10-45 with 116 pounds 2174 dry was used, also the BV; Alternate B formula of 12-30-45, with 44 pounds of 2174 and 225 pounds 2140 dry, Titanox RC. The special carried 40 pounds of 2174 and 80 pounds lead titanate. A series of house paints was prepared for exposure to study more K? precisely the effect of variations in pigment-volume-concentrations. In this series the p.v.c^s were varied in 1$ steps from 25$ up to the regular of 10-4-43 which runs 36.7$. Insofar as it was possible to do so,, the pig mentation was held constant, also the amount of (48). bodied linseed oil,, varying only the raw linseed oil, and adding mineral spirits when necessary #'* to ease brushing. Exposures, rail be south vertical Florida, and south and north vertical Chicago. Results will'have bearing on our post-war formula &W tions. v . We have had difficulty in reproducing viscosity measurements for some types of formulations.- To determine the most accurate method of making viscosity measurements, the viscosity of a sample of SYiP Gloss TJhite was determined over a period of 15 days, using various standard methods. A fresh sample was.used for each test*. 0007-SWP-000018748 -3- M. VAN LOO Cont* The S-Yf Flowmeter was used, "both ty overflowing the cup and ty scraping the paint level -with the top of the cup. The Stonier viscosimeter was used in the normal manner, using a given weight and timing 100 revolu tions of the paddle. An attempt was made to obtain yield values by slowlyadding sand at the rate of 112 gns./nin. up to the first movement of the paddle* The paint was prepared for the viscosity determinations in different ways. In some instances, the samples were not agitated in any way prior to talcing the viscosity, some were shaken, and others were agitated continuously. T?ith the house paint sample differences observed in viscosity readings were slight and for practical purposes no preference was found for any one method. It is planned to extend this work using formulations which have given trouble in the past, to try to establish a more satisfactory nethod for this test. #178 - Studies of Dark Colored House Paints Drying tests were run during the month on normal storage samples of S1YP Modern Brown raid French Green mentioned in earlier reports. After 18 months1 2s3to4rage of samples with and without zinc oxide the following set-totouch times 7/ere observed, as compared with earlier readings: Paint One Week Set-to-touch 10-1/2 Mo. 18 Months 1. STCP 2. SV2P 3. 5Y2P 4. STZP Modern Brown-ZnO as 25# 414 W3 hr.40 min Modem Brown - no ZnO 4 " 50 ,r French Green-ZnO as 25# 414 W 5 H 50 " French Green - no ZnO 7 " 30 n 6 hr. 6" 8' 45 " 6 hr. 8 10 80 " 45 nin. 50 " Improvement through the use of zinc oxide is very apparent. . YJhen this investigation was started it was planned to use acetone soluble determinations to check sol-gel ratios as a function of exposure time, in an attempt to learn something about the "softening-back" of old films of dark colored house paints. However, after the films had been on exposure for some tine, the acetone soluble determinations reversed them selves due to the solubility of the zinc soaps formed in the films of the paints carrying zinc oxide. YShile it~is a relatively simple matter to deter mine the zinc oxide solubilized in the form of zinc soaps, it is difficult to correlate the zinc oxide vdth the fatty acids with which it is combined. Be cause of the inconclusive results, acetone extractions are being discontinued, at least for the tine being. #164 - Reformulation Studies of House Paints to Reduce Dirt Collection Paints have been prepared for exposure to amplify an earlier series, V comparing old and new revisions of Rex 456 SYJP Fume Resisting TJhite end Hex 610 Gas and Fume Resisting TJhite, end adding four tint base fume resisting 0007-SWP-000018749 -4- M. VAN. LOO Cont. #164 - Cont. paints tinted Cream and Slate Gray. All paints will be exposed both selfprimed and over Hex 450 SAP Undercoater, to determine the effect of lead pigments in the primer. The exposures will be at the Chicago exposure farm and the Gloucester Titanium Plant, if possible, A series of oil conservation tests (6385-6912 TP) were examined after 12 months1 exposure Florida, south vertical. The paints include some of Titanium Pigment Corporation's low p.v.c., low n.v.m. house paints with neu tralized vehicles, and Lowe -Brothers' T-2022 and T-2023 developments, as well as some proposed tint bases. The panels are Ponderosa pine siding, prepared in such a way that the following systems are compared on each panel: \ (a) Regular Guide Hex 471 SRP Gloss White over Rex 450 S7IP Undercoater. (b) Test Paint over Rex 450. (c) Test Paint as one coat only. The condition of the Florida panels after 12 months' exposure may be summed up as follows: Materials Tested m Regular Rex 471 Gloss White, pre-conservation. Rating Poorest as to checking, also yellowish cast and considerable mildew. T.P.Corp. EX-3742. P.V.C. 21?. Ho Poorest all-around. Check, crack, and inert, mechanically mixed lead-zinc, tendency to erode. -''Thin" appearance. VM 1939M5 bodied oil vehicle. %lib EX-3743..P.V.C. 21?. Similar, but No failure; clean and white, asbestine used. 4 . One of the best. EX-3742 Reformulated to use cofumed Pb-Zn. Rather poor. Appearance good, but a peculiar failure is starting. Shows pits in vicinity of mildew spots. EX-3743 Reformulated to use co fumed Pb-Zn. Somewhat better. Appearance good, but shows cissing. Lowe Bros, T-2022 - leaded zinc, high inert, R-200 Ti02, LA 740 bodied oil vehicle. Good durability; would rate with the best except for yellowing, as on guide. Same as preceding, but using (48) if bodied oil (this is nearest to our Rex 471 Oil Conservation flhite as finally adopted.) Equivalent to preceding, JifffB * 0007-SWP-000018750 if -5w.- M. VAN LOO Cont. X&\ #164 - Cont. Materials Tested Bating SNP-Conservation Tint Base, Slate, using R 610 Ti02 and high inert. Serious fading, but clean. (A single test of this paint tinted Cream, however, shows good color, better than regular Cream,). Same, but using R 10 titanium Equal to R 610 formula. T.P.C. EX-3746 low N.V.M. Tint Base p.V.C. 21$. Vehicle as EX-3742, about 1/3 each of lead titanate, leaded sine and asbestine* No chalk, no fading, very dirty. No failure. T.P.C. EX-3748 Low N.V.M. Tint Base. Practically same performance as P.V.C. 21$. Pigment 30/70 Leaded preceding. Zinc-Titanox RC, vehicle as above. as- Bex 363 - C'3152. Pre-conservation Tint Base, Slate. Very little fading, but moderate chalk and fairly heavy dirt. This is best for tint-retention. The conservation bases (above) are best for self-cleaning, but fade seriously. The Chicago panels after 11 months' exposure show much the same results. A detailed progress report is in preparation. #86 - Durability of Pigments with Special Reference * to Le1aded Zinc an2d White Lead 3 < There has been considerable discussion among formulators as to the necessity or desirability of using lead pignents in exterior house paint formulas. A study has been initiated to determine the optimum concentration of lead pigments. A series of paints have been prepared for exposure, which include; (1) Variations in lead pigment content from 35$ down to 0%, zinc oxide held constant at 30$. (2) Variations in lead pigment content from 35$ to 0%, zinc oxide content ranging from 50% to 56% to keep Ti02 content at minimum for 18,000 units of opacity. (3) Study of titanium calcium pigmentations, including combinations of 30$ leaded zinc and 70$ of Titanox RC, Titanox RC HT, and anatase titanium calcium, respectively; and 30$ acicular zinc oxide Azo ZZZ #33 with 70$ of Titanox RC HT and anatase titanium calcium, respectively; Exposures Yfl.ll be at Chicago, Coffeyville, and Miami. 0007-SWP-000018751 --6-- M. VAN LOO Cont. ff8S - Cont. Points were prepared for exposure based on Oakland's S-W Liquid Oslo, and a variation of the Liquid Oslo formula with an improved vehicle combination similar to that of SWP Gloss White. Exposures will be put out in Chicago and Florida, both self-primed and over Rex 450* Paints were prepared for exposure comparing the regular oil conser vation formula of 1-22-43 for SWP Gloss White with the lead-sinc-extender formula of 8-10-29, a variation of the latter using 7% mica to reduce check ing, and lead-in-oil using Replacement Oil for reduction. The following com parisons are interesting: To p Coat Paint Brightness Opacity R. M. Costs OJ 23 H Rex 471. Reg. form. 1-22-43 OJ 222 H " " 8-10-29 OJ 224 H As 222 K but Ivt-332 vehicle OJ 225 H As 224 H but 7% mica ' Rex 16 - Lead with Replacement Oil 85.9$ 81.Q* 81.2$ - 84,7$ 19,834 units 16,216 H 16,216 n 16,216 ti 17,495 ,, $135.58 176,57 151.94 -- 192.97 The high initial brightness of lead-in-oil is interesting, also the cost comparisons versus current SWP, #12 - Exterior Primers To reduce the amount of pure Ti02 used in Rex 450 SWP Undercoater, two alternate formulas were developed, in one of which all the Ti02 was intro duced as titanium barium pigment, and the other carrying 50 pounds pure Ti02 and the remainder as titanium barium. The formulas have been distributed to the factories to be used when titanium barium is available and pure Ti02 is in limited supply. A series of experimental SWP Undercoaters were prepared for exposure to compare the current formula with the older type using (2281), For this series the (2281) was prepared respectively from tung, oiticica, and cacahuananche oils. Hie oiticica and cacahuananche modifications dried almost as fa3t as the tung oil type. Exposures will be run at Chicago and Miami. ' Investigation of . the absorption of oil by wood from various vehicles has continued as described previously. It is felt that a summing up of the progress of this project is desirable. The project was started with one-coat house paints and primers as the main subject of interest, especially the possibilities of use of the socalled "neutralized" oils, which are known to have low penetration properties. Hie work done by Dr. Holley and F. M, Nelson, presented in Bulletin RC-52 in August, 1939, was used as a starting basis. Since this work was for the pur pose of sales publicity, a number of changes were required in the method in order to obtain quantitative accuracy. It was also established that a rapid 0007-SWP-000018752 r -7- lir VAN LOO Cont. ffl'S - Cont. reflux-percolation method could satisfactorily replace the longer Soxhlet extraction used ty Nelson. In general, the test material is applied to the surface at a definite spreading rate, allowed to dry a specified time (usually 4 hours), carefully scraped off and its oil extracted by means of a solvent, lights of the original sample scraped off, the oil found after drying and the loss from the extracting flask are the essential data required. The main dif ficulties encountered and the progress toward their solution may be stated briefly: 1. Choice of solvent. At first petroleum ether was thought to be good because it gave a dear extract, free from colloidal pigment particles, which was not true of acetone and ethyl ether. Earlier reports have stated results based on the use of petroleum ether, which must nov( be rejected because fairly recently it has been found to bo not more than 4$ efficient in extracting the semi-dried binder. This was finally settled by running regular determinations using the vehicle binder only rather than the whole paint, part of which work was done in February. As a result, petroleum ether has been rejected as a solvent, and ethyl ether and a blended ether-bensol-nethanol-acetone solvent were found to be 100$ efficient. Several other' solvents were tried; some were suitable, but not readily available. 2. Removal of colloidal pigment particles. After percolation, it is necessary to clear up the fine suspended matter in order to arrive at the true weight of oil extracted. A fritted glass filter was found to be the only type capable of removing the particles, but in some cases it was useless. Some of the best results obtained so far have resulted from the use of the centrifuge and a "direct method," which consists of carrying out the percolation in a bottle which con be whirled in the centri fuge. Incidentally, considerable tine was spent in ignition tests on the final cil obtained to get an idea of the amount of non-organic matter being weighed* 3. Volatile content and miscellaneous. It was found that we could not assume 100 loss of volatile during the usual 4-hour air-dry. Determinations, mainly during January, showed that definite percentages for each paint, in the vicinity of 20% of the original volatile, wore retained try the film, and a correction is now applied. Rather recently it became necessary'to do some checking on the effect of permitting the solutions to stand over night, etc., due to the extra time involved in centrifuging. Most runs have included draw-downs on glass to check the "oil found" values. Due to a temporary shortage of ethyl ether, we could not carry through during the past week or so plans to run final determinations on the paints of aain interest so far, namely Rex 460 Undercoater of 1938, Rex 450 of 1943, and 0007-SWP-000018753 -8- M. VAN LOO Cont. g!2 - Coat. Titanium Pigment Corporation's "neutralised oil" paint, EX-4140. Values from recent runs which seemed to be free from all the main sources of error and which we expect to verify soon, are: Absorbed Paint Solvent Hrs. Drv Surface % of Total Oil Found by Wood Old Rex 450 Blended 4 Codar Glass 73*0 98.0 27.0 - New Rex 450 n 4 Cedar Glass 74.8 101.8 25.2 - EX-4140 it 4 Cedar 76.9 23.1 Glass (No valid check as yet) - ffl.62 - Studies in Flat Wall Paint Formulation Flat Wall Paints. Some difficulties have been encountered with sheen, and body on the new formulas for Flat-Tone white and tints. The regular formula in which the opaque pigment was entirely rutile titanium calcium has been revised to use magnesium silicate 20 L and Micro Velva A 2188 as the extenders to increase the sheen and body. The alternate formulas with lithopone and rutile titan ium calcium gave higher sheen, end thought is being given to the use of Celite 281, 2077 dry, to reduce the sheen. Factory runs are being made at different grinding tines in the pebble mill to determine the effects on grinds and sheen. An Interior Flat or Eggshell Paint was made up on a proposed speci fication submitted by the U. S. Maritime Commission. It was evaluated with respect to brushing, flow, drying, and washability. The paint had satis factory brushing and drying qualities but was short in flow* The washability was not equal to Flat-Tone but was rated as fair compared with an average flat wall paint. Our results were reported to Cleveland. Enamels The continued shortage of'titanium pigments has made it necessary to conserve them vherever possible. Studies were made of alternate pigmentations for Enameloid White Hex 710, which calls for 290 pounds of anatase Ti02, 1403 dry, to reduce `the amount of pure Ti02 required, and to use lithopone, if pos sible. Attempts to replace any substantial amounts of Ti02 with lithopone gave enamels with lowered brightness and opacity# It is impossible to intro duce sufficient lithopone to maintain hiding without getting excessive body. Rutile TiOg such as 2269 Titanox RA-10-MQ, and rutile titanium cal cium pigments like 2132 gave enamels which were decidedly yellow in tone as compared with^standard, Blends of 2269, rutile Ti02 and 1271, anatase titan 0007-SWP-000018754 -9- IS. VAN LOO Cont. ffLSg - Cont. ium calcium, were tried and they proved slightly bettor for color than straight 2152. It xk l s found that the yellow cast of the rutile pigmented enanels could be eliminated at the expense of brightness by tinting with a violet, toner, ihe resulting color impresses the observer as being "neutral? but it is noticeably less bright as compared with that of enamel made with anataso Ti02. CP 498, Permanent Methyl Violet, was used in our experiments. She following pigment combinations (pounds required for 100 gallons of standard formula) had theoretical opacities and brightness readings as shown. Pir^aent 290 pounds 1405 72 pounds 1405, 360 pounds 2152 240 pounds 2132, 145 pounds 1403 480 pounds 2152 300 pounds 461 L, 145 pounds 1403 300 pounds 461 L, 240 pounds 2132 450 pounds 461 L, 72 pounds 1405 600 pounds 461 L 235 pounds 2269 400 pounds 461 L-R7, 127 pounds 1403 400 pounds 461 S-R7, 127 pounds 1403 400 pounds 451 L-K7, 210 pounds 2152 400 pounds 461 S-R7, 210 pounds 2132 300 pounds 2132, 285 pounds 4G1 L-R7 240 pounds 1271, 145 pounds 2269 Opacity 17,690 units 17,712 n 17,725 ii 17,760 ti 14,635 14,676 13,077 n n ii 14,670 n i7,eeo 15,467 15,467 it n it 15,490 n 15,490 n 16,600 n 17,740 ii Briehtne 87$ 85.8# 86.4$ 85.6% 85.8% 84.6% 84.9% 85,5% 87% 65.4% 85.4% 84.3$ 84.4% 84.8% - (1 brush coat on filled white paper) She possibility that Order M-332 may be relaxed to allow the use of more oil, led to some work in connection with Class 5, It was deemed advis able to see what types of enamel could be made with 3-3.25 pounds of oil per gallon, particularly if they were pigmented without the use of titanium. A number of experimental enamels were prepared, using 8-1/2 pounds of lithopone per gallon, end 3 to 3,25 pounds of oil. Some of these enanels showed good gloss and brushing properties, and were similar in properties to our old Eiiamelastic. Typical formula and sample were forwarded to Cleveland Technical Service Department. A brief evaluation was made of National Aniline's "Anti-Skinning Agent B - SC 46326." A laboratory batch of Enaneloid Ivory, formula dated 8-31-39, vras prepared, omitting the amount of (1767), guaiaccl solution called for. The vehicle in this Enaneloid formula is a modified phenolic wood oil varaisb and normally shows bad skinning properties. The enamel ms divided into small portions and varying amounts of different anti-skinning agents were then added. The condition of the enamels in open containers and 4 0007-SWP-000018755 M. VAN LOO Cont, #162 - Cont. in closed containers half-filled was observed at the end of 24 hours. The drying of the enamels was checked using ,003n draw-downs on glass plates. 3he following table shows results: Lab. No. Description Drying Open Can Closed Can Sward 4 Hrs. 24 Hrs. Set 24 Hrs. Hardness (1) No enti-skinning agent (2) 2g ty vol. (17G7) as in Enaneloid formula 8-31-39 Skins Skins Skins Skins tender 901 TF 901 WST 12 12 (5) 2$ by volume (5026) SI. gummy Gunniness partial skin 90* WST 12 (4) 7$ by volume Special Solution O.X. O.K. 90* WST 12 (5) 3$ by volume (5026) o.x. Gumminess 90* VST 12 (6) 5$ by volume Special Solution o.x. O.K. 90* VST 12 (7) 5$ by volume (5026) o.x. O.K. . 90* ST 12 (8) 5% by volume Special Solution o.x. O.K. 90* ST 12 Special Solution - 20# BC 46526 in mineral spirits. (1767) - 14$ Guaiacol in ** (5026) - 20# BC 97261 in At the end of two weeks all samples in both open and closed con tainers had skinned over. Samples containing BC 46526 were the last to show skin formation. The color of BC 46326 is better than that of guaiacol or National Anilinefs 3C 97251. It seems more effective as an anti-skinner than either of these materials. The odor is bad. #105 -- Metal Protective Paints Dr. Ruthruff supplied us with samples of a solid rust inhibitive coating material obtained from Kendall Refining Company, and also a gallon of the material in naphtha solution. These materials were put on exposure at the Chicago exposure farm on cold rolled steel panels, and roll also be subjected to ^eather-Oaeter and salt spray tests. A coal tar pitch T-607 was obtained from idle Coal Tar Plant and will be used as a comparison mat erial. T-607 has 68.3$ solids, and a melting point of 75 C. 0007-: -11- &v H. VAN LOO Cont. tp CLQ5 - Cont. & A program was instituted recently to extend earlier work done by C. West and K. Van Nordstrand, on protection afforded by the use of thin layers of fatty acids and bodied oils on ferrous surfaces. Special attention is being paid to increase or decrease in blister resistance in salt and dis tilled v/ater immersion, salt spray resistance, and effects on rust creep and general durability on exterior exposure. , Four different primers with fourteen different unpigmented filmforming materials are being evaluated. The first coats comprise the following scries: .v>: 1. Stearic acid #.tv 2. Oleic acid 5. Linseed oil fatty acids (2120) 4. Dimerized fatty acids - Diamer A 5. Bodied linseed (48) 6. 11 " (324) 7. Sulphuryl Chloride treated linseed, Bilinco 101 8. Dehydrated Castor (2325) 9. Soya alkyd - (3128) 10. 50? (3128) - 50? (48) M&- 11. Phenolic varnish (5950)H 12. (3950)H - 50?; (48) - 50? 15. Haw linseed (2) 14. Highly polymerized ester gum varnish ($880)E ft;- ft All of the above except stearic and oleic acid contained drier as if- J$f..:. 0.5? Pb and 0.05? Co based upon total solids. All of those materials viere ma7T. reduced to 3? solids and sprayed out as a thin coat on steel panels, which then received a top coat of one of tie follovdng primers: 52-P-18, 52-MC-29, Class XXIX Red Lead and Rex 16174 - Krom-ik. ?<- Blistering tests have been completed on this particular series but discussion vail be deferred until next month, when salt spray tests will be JgU; sufficiently advanced for evaluation. . ' W:: fi{". & A sample of strontium chromate was received recently from the Dry Color Department for evaluation versus sine chromate.. In accelerated tests in the 52-P-18 specification it may be said that the material is superior, to D 2689 end calcium chromate in blistering properties, both in distilled and salt water. It behaves similarly tc Zinc Tetroxy Chromate in this respect. . However, on the basis of salt spray tests, it is inferior to D 2689, but at least equivalent to calcium chromate. ftit Some months ago, salt spray tests were run on.a sample of stron ft-- tium chromate versus other chromates. At that time the chromates were rated in 52-P-18 as follows with respect to performance in salt spray:. 0007-SWP-000018757 h im..... mT'mTui'irfuqiJiaWiii -12- U. VAN LOO Cont. #105 - Cont. J,, K. C. #2815 and D 2689; 2. 12054 dry; 5. Zinc Tetroxy Chromate; 4. Diamond Alkali calcium and Kentucky Color strontium chromates; and 5. K*. C. barium chromate. The similarity of performance of calcium and R. C. strontium chromate would suggest that the Foote Brothers material behaves similarly to that from Kentucky Color. Tifith respect to general performance in primers, the question is best answered in terns of exterior exposure results. Recently it has been noted that rather wide differences in salt spray resistance in primers are ironed out v/hen placed on exterior exposure. Based upon blistering pro perties, hov/ever, the material would be of interest in formulations requir ing good resistance in this respect, but only on the basis of a volume for volume price equivalence rdth Zinc Tetroxy Chromate. At the present time it is about twice that of Zinc Tetroxy Chromate. Special Studies Barge Primer exposures at Florida, part of which were mentioned in the January report, were given a final examination and summarized. The sup plementary set, exposed 9 months, -was described previously; CH 5285 Prefab Primer appeared slightly inferior to stock H 6952 Barge Primer, and our approximation of Barge Paint Gray, Specification 52-MC-13, shov;ed more fading than stock K 6959 Barge Gray from Newark, but actually looked better because the latter had a peculiar greenish cast. The main Barge Primer series, all our experimental primers based on study of Specification 52-MC-12 end quite extensive preliminary tests (includ ing salt and fresh water immersion), were examined after 12 months1 Florida exposure, 45 south. It sliould.be remembered that this is essentially the same as regular house paint test conditions, and may not compare very closely with actual barge use conditions. These panels all had the same top coat, the experimental 52-MC-15 mentioned above, and seven white primers .were tested, both as 5-coat work (two coats of finish paint) and 2-coat work r/ith an edge left unpainted for extreme weathering. All panels looked very much alike except for wood cracking, and about the only criterion of primer effective ness was the tendency to peel in the vicinity of cracks. `In general, phenolic m. and bodied oil primers showed up slightly better than nlkyd vehicle primers. Rex 450 Undercoater and the two alkyd vehicle primers used were the only ones raiere a definite peeling tendency was noticeable. The alkyds were incorporated with the same two pigmentations as used with phenolics and bodied oil on other $: panels, which were in excellent condition. One pigmentation carried no zinc oxide, as per 52-MC-12, the other a snail amount so as to make it similar to CH 3285. No difference was noted. CK 3285 itself appeared good, but not quite equal to the specification primers. i GQ07-SWP-000018758 -13- & VAN LOO Cont. No work was done during the month on the followings #165 - One Coat House Paint #77 - Mildew Inhibitors #160 - Painting of Bricks 2ML - Examination of Tfliite Lead #150 - Durability Studies of Zinc Sulphide Pigment Combinations #112 - Fire Retardant Paints t i >'