Paint Technology and Tests

by Henry A. Gardner

“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																					REPORT OF INSPECTION				Pan- el Num- ber
For- mu- la Num- ber	Basic Car- bon- ate Wh. L’d		Zinc Ox- ide		Basic Sul- phate Wh. L’d		Zinc Lead White		inert pigments
									Calci- um Car- bon- ate		Calci- um Sul- phate		Mag- ne- sium Sili- cate		Bari- um Sul- phate		Silica		Blanc Fixe
																					CHALKING	CHECKING	GENERAL CONDITION	REMARKS
	%		%		%		%		%		%		%		%		%		%
1	30		70		—		—		—		—		—		—		—		—		Slight	None	Good	Slight scaling; fairly white surface	2
2	50		50		—		—		—		—		—		—		—		—		Medium	Very slight	Fair	Panels quite dark and some scaling	4
3	20		50		20		—		10		—		—		—		—		—		Considerable	None	Good	Fairly white	6
4	48	.5	48	.5	—		—		3	.0	—		—		—		—		—		Considerable	Lateral and irregular	Fair	White surface	8
5	22		50		—		—		2		—		26		—		—		—		Medium	Very slight	Very good	Extremely white surface	10
6	—		64		—		—		—		—		—		36		—		—		Very slight	Very bad; rough surface	Poor	Black surface	12
7	37		63		—		—		—		—		—		—		—		—		Slight	Slight	Good	Medium white surface	14
8	38		48		—		—		—		—		—		—		14		—		Slight	Slight	Good	White surface; slight scaling	16
9	—		73		—		—		2		—		—		—		25		—		None	Deep; peeling in places	Very poor	Film brittle and surface dark	18
10	44		46		—		—		5		—		5		—		—		—		Medium	Slight lateral in places	Good	Surface very white	20
11	50		50		—		—		—		—		—		—		—		—		Considerable	Deep matt checking	Fair	Considerable scaling; formation of black coating shattered off	22
12	60		34		—		—		—		6% Inert Pigment										Medium	Slight	Fairly good	Surface white	24
13	—		27		60		—		3		—		10		—		—		—		Medium	None	Excellent	Very white	26
14	25		25		20		—		5		25		—		—		—		—		Considerable	Medium	Fair	Panel fairly white	28
15	20		40		—		30		10		—		—		—		—		—		Slight	Medium	Good	Surface quite dark	30
16	33		33		—		—		—		—		—		34		—		—		Medium	Very slight	Good	Quite white	32
17	40		40		—		—		—		—		3		13		—		4		Considerable	Slight, along lateral lines	Fair	Surface fairly white	34
18	75		25		—		—		—		—		—		—		—		—		Medium	Slight, with some scaling	Good	Surface has become quite dark	36
19	—		25		75		—		—		—		—		—		—		—		Considerable	None	Excellent	No black coating; surface very white, due to inertness of pigment or progressive chalking	38
20	67	.0	19	.5	—		—		10	.0	—		3	.5	—		—		—		Medium	Medium	Good		40
33	15		30		25		—		—		—		—		—		30		—		Heavy	None	Fair	White surface	168
34	38	.95	33	.58	4	.81	—		19	.48	—		—		1	.59	1	.59	—		Considerable	Very slight	Good	Surface is very white; progressive chalking may have prevented formation of black coating	172
35	37	.51	25	.87	7	.84	—		20	.36	—		—		4	.21	4	.21	—		Bad	None	Good	Very white; no black coating evi- dent	173
36	100		—		—		—		—		—		—		—		—		—		Bad	Bad	Fair	Surface is dead black; shattered in places	174
37	100		—		—		—		—		—		—		—		—		—		Extremely	Medium	Fair	Very black surface and mottled in places	175
38	100		—		—		—		—		—		—		—		—		—		Very bad and quite dusty	Very bad, with scaling	Poor	Black surface is loose and shattered	176
39	—		—		—		100		—		—		—		—		—		—		Considerable	Slight	Good	Panel surface quite white	177
40	—		—		100		—		—		—		—		—		—		—		Very bad	Slight	Good	Surface very white, possibly due to progressive chalking or inert- ness of pigment	178
45	—		90		—		—		10		—		—		—		—		—		Slight	Considerable	Fair	White surface	169
46	—		61		—		—		—		—		—		—		39		—		Slight	Slight	Fair	Considerable scaling present; sur- face fairly white	170
47	—		100		—		—		—		—		—		—		—		—		Bad	Bad	Bad	Bad condition throughout	171

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. Scrapings from the different panels are being taken, and after a careful analysis 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’ Association
John Dewar.	Member Fence Committee, Pittsburg Branch, Penna. State Association 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. Asso. of U. S.