CHAPTER IX_Paint Technology and Tests

RESULTS OF PITTSBURG TESTS

The First Annual Inspection of the Pittsburg Test Fence took place

during May, 1909, a little over one year after the painted panels had

been placed in position. The inspectors found that in Pittsburg a heavy

deposit of soot had formed on the panels, and they considered it

therefore inadvisable to make a detailed report of the inspection until

the second year of the exposure. The general results of the Pittsburg

inspection as reported by the three committees[22] having supervision

over the work, is, however, given herewith.

[22] J. H. James, Chairman Test Fence Committee, Carnegie Technical

Schools.

A. C. Rapp, Chairman Fence Committee, Pittsburg Branch

Pennsylvania State Association of Master Painters.

R. S. Perry, Director Scientific Section, Paint Manufacturers'

Association of the U. S.; H. A. Gardner, Asst. Director.

[Illustration: Pittsburg Test Fence]

During the inspection of the Pittsburg tests it was decided to condemn

the lithopone panels on the fence, which consisted of formulas 21 to 27,

including panels 151 to 164 in white, 131 to 144 in yellow, 109 to 122

in gray. Almost complete failure had taken place in every case where

lithopone had been used. These lithopone tests were later on replaced by

new tests which are described later in this book.

"=Wood Most Valuable for Test.= As on the Atlantic City Fence, the white

pine panels afforded the best results and gives the best indication of

the comparative wearing of the paints and affords no unfair condition,

such as other woods might offer, to interfere with the test.

"=Condition of Cypress.= Cypress showed inferior conditions, except that

it was more pronounced and more discoloration of the panels was noticed

on this grade of wood, which seems to be extremely greasy in nature and

difficult to properly prime, even when the paint used upon this wood

contains a large percentage of volatile diluent.

"=Removal of Lithopone Panels.= The Joint Committees confirmed the

previous recommendation to remove all the lithopone formulas, and they

decided to remove the cypress and the yellow pine panels in every

formula except in the white paints.

"It was decided to reassemble all the white pine panels and group them

together for purposes of comparison, and in place of the panels

condemned and removed, to substitute a series of new formulas, to

further widen the scope of the tests.

"=Ultimate Value of Mixed Paints.= The results of the inspection

conclusively show that a mixture of more than one prime white pigment,

whether this mixture be alone or in combination with a small percentage

of inert pigment, produces a paint far superior to a paint manufactured

from one pigment alone.

"As a general statement of the comparative wearing of the paints, it

might be said that the composite formulas are less advanced toward

destruction than the paints made from single pigments such as

lithopones, white leads and zinc oxides. It is not to be understood from

this statement that it is the opinion of the committee that all of the

composite formulas are of equal value or that all of them are to be

recommended, but it is meant that the higher types, as evidenced by the

appearance of the panels, are in the above relation to the single

pigment paints.

[Illustration: Panels on Pittsburg Test Fence]

"=Lithopone Destroyed Rapidly at Pittsburg.= It was evident some time

ago that the formulas containing large percentages of lithopone were

rapidly failing, and their appearance was very much the same as those

formulas of a similar type at Atlantic City. There seems, however, to be

some difference in the way these formulas broke down; those on the

Pittsburg Fence having shown the quicker destruction, possibly due to

the action of the acid gases in the air upon the paint coating. This

further confirms the statement that paint compositions containing such

heavy percentages of lithopone and intended for outside use must be

designed with relation to the particular uses of the product and to the

climate in which they are to be used. It will also be necessary to

consider more carefully the vehicle of the paints which are to be made

of this pigment.

"=Possible Value of Excluding Vehicle for Lithopone.= It was the belief

of the committee that much better paints containing lithopone could be

formulas, and it was suggested that a less penetrable vehicle, made more

on the line of a varnish, and not as easily affected as straight

linoxyn, should be experimented with in connection with these lithopone

formulas.

"The success of certain European countries in using lithopone as a

pigment, even in a very high percentage, may be due to the use of a

special vehicle, and, if it is found in future tests that this material,

which has been reported as well suited in Northern European climates,

may be benefited and made of service by the addition of special oils and

special vehicles, then this test would be of great value to the whole

paint trade at large.

"Preliminary inspections were made on October 6th and later on December

12th, 1908, and a marked difference was observed at the two inspections

in the wearing of the various formulas.

"The lapse of the two months between these inspections gave opportunity

during which cold weather caused contraction of the paint film which had

been previously subjected to the hot summer sun, and caused marked

chalking of the white lead formulas. On October 6th this chalking was

just commencing, while in the December inspection it was well advanced,

and at the annual inspection, had proceeded to such an extent that the

pigment had been washed from the panels representing those paints which

had started early chalking.

"Panel 177, representing Zinc Lead, was found to be extremely dark in

color throughout the coating and was more on the order of a grayish

tint. It resisted all attempts to wash it down to a white surface. The

panel, however, in other respects, was in fairly good condition.

"=Condition of Corroded White Lead Panels.= Panel 174, representing Type

B Pure Basic Carbonate-White Lead, was very badly perished and

discolored, and an examination of the surface showed very bad checking.

Long continued washing with a sponge removed a discolored surface and

showed but a rather thin coating. Panel 175, representing Type C Pure

Basic Carbonate-White Lead, showed most marked checking and was in very

much the same condition as 174 and 176. Panel 176, representing Type A

Pure Basic Carbonate-White Lead, was in the same condition as the Type B

and C Basic Carbonate-White Leads.

"=Condition of Sublimed White Lead.= Panel 178, representing Sublimed

White Lead (Basic Sulphate-White Lead,) was chalking, and the paint coat

was somewhat disintegrated. The chalking present on this formula,

however, showed that the disintegration of the paint coat had not taken

place for several months after the Basic Carbonate-White Leads. This

panel maintained good color, not being acted upon by sulphur gases.

"=Blackening of Corroded White Lead.= The black and gray formation on

all the Basic Carbonate-White Lead panels was probably due to the action

of sulphur gases which are present in the district immediate to

Pittsburg, and which may cause the formation of black sulphide of lead.

"Possibly a general conclusion from all these panels might be described

as a perishing of the paint coating, with the formation of sulphide of

lead which to a certain extent protects the coating beneath it, but the

perishing has proceeded to such an extent that the unaltered paint

coating left is but a slight protection to the wood, being extremely

thin.

"The committee resolved that the detailed observations of the panels

could not be made and that they would not be justified in making

detailed comparisons between the various formulas, giving the gloss,

hardness, general condition, checking, etc. Precision in this work at

such a time was impossible, and it was decided that a further period

would have to elapse before such a detailed comparison could be made

between the various blended or composite formulas on the fence.

"=Report on Colors.= It was resolved that at the next inspection of the

Pittsburg Fence, portions of the original samples of the original paints

used for the yellows and grays should be on hand, previously painted out

on small panels for comparison for the deterioration of the colors on

these same panels on the fence.

"An examination of the combination formula grays by the committee led to

the general conclusion that those grays which did not contain a very

large percentage of white lead were superior in their maintenance of

tone and tint and general condition to any of the other grays upon the

fence. However, the presence of umber, ochre, and red oxide in some of

the grays which showed to the best advantage may account for their

permanence of tone. Some of these grays were the so-called warm grays

and were much darker in tone and tint than the ordinary drab which is

generally applied.

"The straight pure Basic Carbonate-White Lead paints were not painted

out in grays or yellow, the test upon this material being only in white.

"On Panels 120 and 126, which represent formulas 6 and 9 respectively,

the grays are in most excellent condition, and it will be found, by

reference to formulas 6 and 9, that there is an absence of white lead in

their composition. These formulas, however, contained a small percentage

of umber and ochre. Formulas 5 and 16 contained over 20% White Lead and

the gray of these formulas maintained their blue tone very well. These

formulas were tinted solely with lampblack.

"An inspection of Panel 138, which represents Formula 15, showed good

maintenance of color in the gray, and was in much better condition as

regards permanence of color than the other grays containing white lead.

"A study of the yellow panels on the fence led to the unanimous

conclusion that a liberal amount of Basic Carbonate-White Lead seemed to

have a beneficial result in preserving the bright tone of the chrome

yellow in tints so strong as those used on the fence. It was noted that

Panel 108, which represents Formula 28, and in which zinc yellow was

used, showed great permanence of tone and tint. Unfortunately this zinc

chromate was added to a formula containing a large percentage of

lithopone, and the destruction of the lithopone to a great extent

affected the value of this test.

[Illustration: Whiteness of Sublimed White Lead

Darkness of Corroded White Lead

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 shellacking, obtained also on the Pittsburg Fence,

namely, that application of the shellac to the wood previous to the

first coat is the better method.

"=Analysis 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 analysis.

The analyses 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' Association, 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' Association; John Dewar, member Fence Committee,

Pittsburg Branch, Pennsylvania State Association 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' Association 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 glass. 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.

[Illustration: 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 |

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 |-- | --|-- |--|-- |-- |-- |-- |

==+======+======+======+===+=====+==+====+=====+=====+===+

==+========================================+===

F | |

o | |

r | | P

m | | a

u | | n

l | | e

a | | l

| REPORT OF INSPECTION |

N +-----------+------------+------+--------+ N

u | | |GENE- | | u

m | | |RAL | | m

b | | |CON- | | b

e | | |DI- | | e

--+-----------+------------+------+--------+---

| | | |off |

35|Bad |None |Good |Very |173

36|Bad |Bad |Fair |Surface |174

|bad | | |black |

| | | |and |

| | | |in |

| | | |and |

| | | |ed |

47|Bad |Bad |Bad |Bad con-|171

| | | |out |

==+===========+============+======+========+===

[Illustration: 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._

_May 31, 1910_

PITTSBURG TEST FENCE

COMPARATIVE SPREADING RATES OF WHITE PAINT ON WHITE PINE PANELS

_Average Spreading Rate 266 Square 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

=======+===========+===========+===========+==========+==============