Part 14 Paint Technology and Tests

Part 14

On Pittsburg Test Fence]

"=Maintenance of Para Reds.= A study of the paranitraniline or azo reds painted over the various pigments as priming coats demonstrated that the reds on this fence are in better condition than the reds at Atlantic City. As is well known, para red is manufactured by precipitation in an acid solution and is best maintained under acid conditions. The acidity of the Pittsburg atmosphere, caused by the large amount of acid gases which are being poured into the air, day in and day out, and which are constantly condensing on the surface of structures, may account for the better preservation of these reds.

"It was noted that the para reds which were applied to panels prime coated with white lead seemed to be brightening in color and seemed to be gradually working over toward a lightening which may in the future show a pinkish tint.

"=Report on Greens.= The bronze green is in most excellent condition and shows an absence of the mildew appearance which was observed at Atlantic City.

"The chrome green is standing up exceedingly well, there being practically no change whatsoever in the color since it was exposed.

"=Best Base for Blues.= An inspection of the blues showed that those which gave the greatest permanence and the least amount of fading were applied in combination with either Sublimed White Lead (Basic Sulphate-White Lead), or zinc oxide, while those blues which were applied in combination with Basic Carbonate-White Lead showed marked failure and were completely bleached out, due, of course, to the alkaline nature of the corroded white lead; Prussian blues being transformed by alkalies to a white compound.

"=Superior Value of Composite Formulas.= Some of the mixed leads, or so-called graded leads, which are combinations of white leads with other high-grade pigments and containing some inert pigments, were not deteriorated so far as the white lead formulas, and the general conclusion was that they were upward of six months behind the deterioration of the straight white leads, and this was confirmed by the presence of moderate chalking, showing an excellent repainting surface and a better thickness and condition of the paint coating.

"The same conclusions which were reached at Atlantic City, as to the best method of sh.e.l.lacking, obtained also on the Pittsburg Fence, namely, that application of the sh.e.l.lac to the wood previous to the first coat is the better method.

"=a.n.a.lysis of Paints.= At the time of the painting of the fence a sample of each paint was placed in small friction top cans, carefully labeled, and sent to the Carnegie Technical Schools' laboratory for a.n.a.lysis.

The a.n.a.lyses of these paints were made by members of the Test Fence Committee, representing the schools, and appear in this bulletin. The results obtained conform very closely to the formulas which were applied to the fence, a variance of only one or two per cent. being shown in the amount of the different pigments."

=Second Annual Inspection of Pittsburg Test Fence.= The second annual inspection of the Pittsburg Test Fence was made on Thursday, May 7th, 1910. The panels in Pittsburg after having weathered for over two years presented an appearance which allowed the making of a detailed inspection, this having been found impossible during the first annual inspection. The inspection party[23] included those master painters who represented the Pittsburg Master Painters' a.s.sociation, who were in charge of the application of the paints in 1907, 1908, and 1909, together with the test fence committee from the faculty of the Carnegie Technical Schools, and representatives of the Scientific Section. A summary of the report issued by this committee follows:

[23] A. C. Rapp, Chairman, Test Fence Committee, Pittsburg Branch, Master Painters' a.s.sociation; John Dewar, member Fence Committee, Pittsburg Branch, Pennsylvania State a.s.sociation of Master Painters; J. H. James, Chairman, Carnegie Technical Schools' Test Fence Committee; John A. Schaeffer, member Test Fence Committee, Carnegie Technical Schools; Henry A. Gardner, Director Scientific Section, Paint Manufacturers' a.s.sociation of the U. S.

"Two of the members of the inspection party have been impressed with the lumber lottery existing in some field tests, which have been conducted, and feel that when the object of a test is to determine the relative value of paints, such tests should be conducted on a standard grade of wood, such as white pine. The use of cypress, pitch pine, and other faulty woods, is often the cause of the failure of a paint, which on good wood would show up well. For this reason, only the white pine panels painted with white paints were considered in the inspection, the yellow pine panels and cypress panels having been thrown out of the test at last year's inspection.

"Checking, cracking, and alligatoring on the painted surfaces were determined by using a magnifying gla.s.s. The degree of chalking existing was decided upon by using small pieces of black felt cloth, rubbing them against the surface of the panel; the degree of whiteness removed upon the cloth being indicative of the amount of chalking taking place.

General condition was decided upon after carefully weighing the opinion of each member of the inspection party, as regards the general characteristics shown by each paint, such as checking, chalking, scaling, condition for repainting, hiding power, etc. The results have been charted and presented in this manner:[24]

[24] An endeavor was made to use uniform terms in reporting on each formula. In some cases it was necessary to bring out more forcibly the condition by the insertion of qualifying remarks.

[Ill.u.s.tration: Panel on Left Painted with Single Pigment Paint; Panel on Right Painted with Combination Pigment Paint. Photograph taken after Two Years' Exposure on Pittsburg Test Fence]

"=Conclusions Reached from the Test.= The primary object of the test made at Pittsburg was to determine whether a combination paint, made of two or more pigments, would be equal or superior to single pigment paints. After one year's exposure, the combination type of paint proved more durable than the single pigment paints.

"It was early apparent that the combination type of paints, that is, those paints made of more than one pigment, indicated in most cases very excellent wear, with a minimum of blackness and a general good condition of surface.

TESTS INAUGURATED IN 1907

CHART OF RESULTS OF SECOND ANNUAL INSPECTION OF PITTSBURG TEST FENCE, MAY, 1910

=========================================================+ FORMULAS | --+------------------------+-----------------------------+ F | | INERT PIGMENTS | o | +-----------------------------+ r |Basic Carbonate |Calcium | m |Wh. L'd |Carbonate | u | |Zinc Oxide | |Calcium | l | | |Basic | |Sulphate | a | | |Sulphate | | |Magnesium | | | |Wh. L'd | | |Silicate | N | | | |Zinc | | | |Barium | u | | | |Lead | | | |Sulphate | m | | | |White| | | | |Silica | b | | | --+ | | | | | |Blanc| e | | | | | | | | | | Fixe| r | | | | | | | | | --+ | --+------+------+------+---+-----+--+----+-----+-----+---+ | % | % | % | %| % | %| % | % | % | % | 1| 30 | 70 | -- | --|-- |--|-- |-- |-- |-- | 2| 50 | 50 | -- | --|-- |--|-- |-- |-- |-- | 3| 20 | 50 | 20 | --|10 |--|-- |-- |-- |-- | 4| 48.5 | 48.5 | -- | --| 3.0 |--|-- |-- |-- |-- | 5| 22 | 50 | -- | --| 2 |--|26 |-- |-- |-- | 6| -- | 64 | -- | --|-- |--|-- |36 |-- |-- | 7| 37 | 63 | -- | --|-- |--|-- |-- |-- |-- | 8| 38 | 48 | -- | --|-- |--|-- |-- |14 |-- | 9| -- | 73 | -- | --| 2 |--|-- |-- |25 |-- | 10| 44 | 46 | -- | --| 5 |--| 5 |-- |-- |-- | 11| 50 | 50 | -- | --|-- |--|-- |-- |-- |-- | 12| 60 | 34 | -- | --|-- | 6% Inert Pigment | 13| -- | 27 | 60 | --| 3 |--|10 |-- |-- |-- | 14| 25 | 25 | 20 | --| 5 |25|-- |-- |-- |-- | 15| 20 | 40 | -- | 30|10 |--|-- |-- |-- |-- | 16| 33 | 33 | -- | --|-- |--|-- |34 |-- |-- | 17| 40 | 40 | -- | --|-- |--| 3 |13 |-- | 4 | 18| 75 | 25 | -- | --|-- |--|-- |-- |-- |-- | 19| -- | 25 | 75 | --|-- |--|-- |-- |-- |-- | 20| 67.0 | 19.5 | -- | --|10.0 |--| 3.5|-- |-- |-- | 33| 15 | 30 | 25 | --|-- |--|-- |-- |30 |-- | 34| 38.95| 33.58| 4.81| --|19.48|--|-- | 1.59| 1.59|-- | 35| 37.51| 25.87| 7.84| --|20.36|--|-- | 4.21| 4.21|-- | 36|100 | -- | -- | --|-- |--|-- |-- |-- |-- | 37|100 | -- | -- | --|-- |--|-- |-- |-- |-- | 38|100 | -- | -- | --|-- |--|-- |-- |-- |-- | 39| -- | -- | -- |100|-- |--|-- |-- |-- |-- | 40| -- | -- |100 | --|-- |--|-- |-- |-- |-- | 45| -- | 90 |-- | --|10 |--|-- |-- |-- |-- | 46| -- | 61 |-- | --|-- |--|-- |-- |39 |-- | 47| -- |100 |-- | --|-- |--|-- |-- |-- |-- | ==+======+======+======+===+=====+==+====+=====+=====+===+

[Ill.u.s.tration: Middle white panel is painted with a combination pigment formula

Middle white panel is painted with pure Corroded White Lead

Notice Difference in Color after Two Years' Wear]

"=Recommendation.= On account of the peculiar conditions which obtain in and around Pittsburg, as exemplified by these tests, the committee finds, as a result thereof, that the best white paint for general exterior use is made of white lead combined with zinc oxide and a moderate percentage of inert pigments, such as silica, asbestine, or barytes.

"=Some Peculiar Conditions Affecting the Tests.= The inspectors were most impressed during the inspection by the blackness exhibited to such a high degree by certain panels, and the fair degree of whiteness by others. It is well known that in Pittsburg nearly all paints become darkened by the deposition on their surface of carbon particles emanating from the combustion of soft coal. Certain of the paints, however, presented fairly white surfaces, and it would thus appear that the extreme darkness shown by other paints was due to their composition.

Corroded white lead when used alone was uniformly covered by black particles, and the higher the percentage of corroded white lead in a paint the darker was the surface. It was at first thought that this darkness was due to the softness of the white lead pigment or to its roughened surface, in causing adherence of soot particles. Sublimed white lead, however, which is also a soft pigment, chalked even more progressively than corroded white lead, but its surface was not rough, and presented a very white appearance. Sc.r.a.pings from the different panels are being taken, and after a careful a.n.a.lysis the findings from the investigations will be reported by a member of the Inspection Committee."

A. C. RAPP. _Chairman Test Fence Committee, Pittsburg Branch, Master Painters' a.s.sociation_

JOHN DEWAR. _Member Fence Committee, Pittsburg Branch, Penna. State a.s.sociation of Master Painters_

J. H. JAMES. _Chairman Carnegie Technical Schools' Fence Committee_

J. A. SCHAEFFER. _Instructor in Chemical Practice, Carnegie Technical Schools Pittsburg, Pa._

H. A. GARDNER. _Director Scientific Section, Paint Mfrs. a.s.so. of U. S._

_May 31, 1910_

PITTSBURG TEST FENCE

COMPARATIVE SPREADING RATES OF WHITE PAINT ON WHITE PINE PANELS

_Average Spreading Rate 266 Square Feet_

=======+===========+===========+===========+==========+============== Formula|First Coat |Second Coat|Third Coat | Average |Spreading Rate Number | (sq. ft.) |(sq. feet) | (sq. ft.) |Spreading | Rate | | | | Rate | 3-Coat Work | | | |(sq. feet)| (sq. feet) -------+-----------+-----------+-----------+----------+-------------- 1 | 759 | 1020 | 768 | 849 | 283 2 | 694 | 975 | 1229 | 966 | 322 3 | 743 | 873 | 770 | 795 | 265 4 | 537 | 987 | 1019 | 848 | 283 5 | 509 | 896 | 886 | 764 | 255 6 | 765 | 1045 | 994 | 935 | 312 7 | 734 | 922 | 996 | 884 | 295 8 | 565 | 862 | 854 | 760 | 253 9 | 622 | 926 | 1160 | 903 | 301 10 | 610 | 1013 | 1070 | 900 | 300 11 | 651 | 933 | 1010 | 865 | 288 12 | 675 | 1027 | 623 | 775 | 258 13 | 663 | 892 | 981 | 845 | 282 14 | 498 | 785 | 807 | 697 | 232 15 | 688 | 1000 | 984 | 891 | 297 16 | 669 | 880 | 860 | 803 | 268 17 | 635 | 982 | 1077 | 900 | 300 18 | 636 | 959 | 1031 | 875 | 292 19 | 626 | 1076 | 1037 | 913 | 304 20 | 591 | 1015 | 929 | 845 | 282 21 | 595 | 948 | 910 | 818 | 273 22 | 617 | 868 | 810 | 765 | 255 23 | 549 | 1002 | 986 | 846 | 282 24 | 539 | 918 | 783 | 747 | 249 25 | 530 | 929 | 850 | 770 | 257 26 | 532 | 916 | 1011 | 820 | 273 27 | 520 | 850 | 656 | 675 | 225 33 | 600 | 1340 | 810 | 917 | 306 34 | 471 | 743 | 690 | 635 | 212 35 | 402 | 598 | 645 | 548 | 183 36 | 398 | 668 | 838 | 635 | 212 37 | 579 | 653 | 838 | 690 | 230 38 | 463 | 615 | 704 | 594 | 198 39 | 474 | 954 | 849 | 759 | 253 40 | 446 | 815 | 871 | 711 | 237 45 | 527 | 841 | 916 | 761 | 254 46 | 605 | 740 | 818 | 721 | 240 47 | 735 | 961 | 993 | 896 | 299 =======+===========+===========+===========+==========+==============

CHAPTER X

A LABORATORY STUDY OF TEST PANELS

=Panel Sections for Laboratory Test.= In order to make a laboratory study of the painted panels on the Atlantic City and Pittsburg fences, it was thought advisable to remove small sections from representative areas and transfer them to the laboratory for such work. The fences were visited by the official inspection committees soon after the first annual inspection, and the panels were carefully looked over. Upon each was marked out a representative portion, care being exercised to select areas where previous inspections had not disturbed the surface of the film in any manner. The inspectors then placed the number of the panel upon the areas which had been marked off, as well as their initials. The marked sections were sawed out, wrapped in tissue paper, and then transferred to the laboratory where they were placed upon models of the respective fences from which they had been removed. The ill.u.s.tration shows the model test fences set up together. It is very apparent that the Pittsburg panels are much the darker in color, due to the soot, and in some cases lead sulphide formed upon their surfaces. This difference was undoubtedly due to the atmospheric conditions prevailing where the tests were made. One would be led to suppose that a paint film exposed to an atmosphere such as is found in Pittsburg would show deterioration more rapidly than one exposed in Atlantic City. In all the tests and experiments, however, the Atlantic City panels appeared broken down to a much greater extent; though it is true that the Pittsburg panels had darkened considerably and presented a rather mottled appearance. The deposit of soot on the Pittsburg panel seemed to act as a preservative coating for the film beneath, and prevented marked disintegration.

[Ill.u.s.tration: Sections of Atlantic City and Pittsburg Fences Arranged for Laboratory Examination]

[Ill.u.s.tration: Sections of Atlantic City and Pittsburg Fences]

[Ill.u.s.tration: Upper set of tests made on Panels from Atlantic City Fence

Lower set of tests made on Panels from Pittsburg Fence

Figures at left indicate Formula Number

Figures at right indicate Degree of Chalking]

[Ill.u.s.tration: Color Standard used in Comparison of Panel Section]

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