Paint Technology and Tests Part 12

CHAPTER VII

CONDITIONS NOTED AT INSPECTION OF TESTS

=Inspection of Atlantic City Tests.= During the month of March, just one year after the placing of the painted panels on the Atlantic City fence, an inspection was made jointly by a committee representing the Master Painters' a.s.sociation of Pennsylvania, the Scientific Section of the Paint Manufacturers' a.s.sociation of the United States, and certain members of sub-Committee E of the American Society for Testing Materials.

=Methods Used at Inspection.= One of the most important tests made when inspecting paint is the determination of the chalking taking place.[19]

There was developed during the inspection of the Atlantic City panels a new method for determining the comparative chalking of the various paints. It was thought desirable to secure a method, if possible, that would show results which might be photographed and even tabulated in percentage form, if desired. The apparatus for the new test consisted of a small strip of black felt three inches wide by five inches long, placed across a small block of wood which would fit in the palm of the inspector's hand. This outfit resembled a blackboard eraser and was used in a similar way. By holding the apparatus firmly against the panel and drawing it half-way across the panel in a straight line toward the operator, there was obtained on the black cloth a white mark proportional in intensity to the amount of chalking which had taken place on the given area. When a series of these cloths were made, they were a.s.sembled and photographed for comparison. It should be noted that the above chalking test is useful only where the painted panels under examination have been exposed over a period of one to two years, during which period the chalking of paints has been shown to be greatest and the chalked surface of a fairly adherent nature. Where longer exposures have been made and where rains have removed from the painted panels a considerable amount of the chalked pigment which has formed, such a test would not be fairly representative of the amount of chalking which had taken place.

[19] Mr. Macgregor of the Picher Lead Co. has just developed a new test to determine the relative imperviousness of paints which have begun to chalk. He draws a mark about two inches long upon the painted surface with a fountain pen. The ink mark will spread rapidly to a wide area if the chalking is of a bad order. If the chalking is slight and the film in good condition, the ink mark will not spread.

[Ill.u.s.tration: Series of Black Felt Cloths used in making the Chalk Tests on the Various Formulas. Numbers over Cloths represent Panels]

[Ill.u.s.tration: CHALKING.--Type of Decay Exhibited by Improperly Made Paint (magnified view)]

[Ill.u.s.tration: CHECKING.--Type of Decay Exhibited by Improperly Made Paint (magnified view)]

[Ill.u.s.tration: BLISTERING.--Type of Decay Exhibited by Improperly Made Paint (magnified view)]

[Ill.u.s.tration: CRACKING.--Type of Decay Exhibited by Improperly Made Paint (magnified view)]

[Ill.u.s.tration: GENERAL DISINTEGRATION.--Type of Decay Exhibited by Improperly Made Paint (magnified view)]

[Ill.u.s.tration: SCALING.--Type of Decay Exhibited by Improperly Made Paint (magnified view)]

=Gloss.= The gloss of the various panels was a condition which was also reported upon, the middle board of each panel being washed with a wet sponge one day before the inspection so that any surface dirt might be removed. By looking at a panel from the side, a day after the washing, the inspector was enabled to get a fair idea of the degree of gloss exhibited by each formula.

=Hiding Power.= The hiding power of each paint was determined, as before described, by observing the degree to which the stencilled lampblack cross on the priming coat was visible through the second and third coats. Single pigment paints such as white lead possessed very great hiding power and obscured the black cross almost completely, while the cross was quite visible through paints containing high percentages of crystalline pigments.

=Checking.= The checking of each panel was determined by examining with a small high-power hand gla.s.s magnifying fifteen diameters. It is well known that examinations with such a hand gla.s.s will not determine whether so-called fine matt checking is taking place, but it will determine whether checking has appeared to any marked extent. Fine matt checking is the first sign of the decomposition of a paint, and is preliminary to the visible checking seen by the naked eye, which is often followed by alligatoring. Examination of some formulas disclosed this so-called alligatoring and even the exposed wood between the fissured surface which had developed from what were at first fine hair checks. It is, in the opinion of the writer, possible to predict with a fair degree of accuracy by examination of a painted surface, one year after exposure, how the paint will wear in the future and what its appearance will be at the end of another year.

=Hardness.= The hardness of each panel could not be determined with any degree of accuracy, but the inspectors were able to roughly determine this condition by very close inspection. From practical experience of the wearing of white lead and zinc oxide, and the comparative hardness of these two pigments, zinc oxide was selected as the maximum for hardness and termed number 10, while white lead was selected as the minimum and termed number 1. The varying degrees of hardness exhibited by the formulas were recorded in terms from one to ten. This comparison of course was only an approximate one.

=General Condition.= The so-called general conditions of the panels was, as a rule, the consensus of the judgment held by the various inspectors, with due regard to such properties as chalking, checking, gloss, hiding power, color maintenance, condition of surface, etc.

CHAPTER VIII

RESULTS OF ATLANTIC CITY TESTS

=Results on Various Woods.= On the Atlantic City Fence all the tests made on yellow pine and cypress were found to be in an unsatisfactory condition for a report, for in every case the sap and small knots contained in such wood had a very bad effect upon the paint, causing peeling and scaling. The white pine panels were in very much better condition, and it was therefore decided to make the inspection entirely from the white pine panels and in the future to remove the yellow pine and the cypress panels from the fence and from the test. The Committee advised that all future tests be made on white pine, as it is obviously unfair to use anything but the highest grade wood for a paint test in which the desire is to determine the comparative wearing value of pigments.

NOTE.--Recent tests have shown that Cypress may be successfully painted when the priming coat of paint is thinned with Benzol (Solvent Naphtha).

[Ill.u.s.tration: Panels on Atlantic City Fence Two Lower Sets of Panels are painted with Lithopone Paints. Rapid Failure shown]

[Ill.u.s.tration: Panels on Atlantic City Fence]

[Ill.u.s.tration: Panels on Atlantic City Fence

Two Lower Sets of Panels are Painted with Combination Pigment Paints.

Excellent Results shown]

=Paints Containing Lithopone.= One of the most striking exhibitions of paint disintegration in the whole test was the failure of nearly all the lithopone formulas tested. At the time these formulas were suggested for the test, various European technical journals had advocated the use of lithopone in large percentage for paints to be used on exterior surfaces. Good results had been obtained in the northwestern section of Europe, with this pigment in certain mixtures, and the object of these lithopone tests at Atlantic City and Pittsburg was to determine whether satisfactory paints could be made of this pigment for exposure in this country. Failure of the tests, however, in nearly every case except where zinc oxide and whiting were mixed with the lithopone, indicated that pigments such as zinc and whiting are necessary in order to prevent the decomposition of lithopone pigment paints. The decay of lithopone paints after they are applied seems to start with rapid oxidation of the linseed oil, and this oxidation seems to continue in a progressive and even accelerated way; after six months' exposure the surface of the paint being chalked to a great extent and showing rapid decomposition of the binder or vehicle. Inasmuch as lithopone is really an inert pigment, this rapid decomposition of its vehicle cannot be explained in the same way as the decomposition of the vehicle of pure white lead paints, where the alkaline nature of the lead is probably responsible for the formation of easily destroyed compounds. As complete failure had taken place in nearly every case where lithopone had been used, it was decided to condemn the lithopone panels on the fence, consisting of formulas 21 to 27, including panels 151 to 164 in white, panels 131 to 144 in yellow, and 109 to 122 in gray. These lithopone tests were later on replaced by new tests in 1909, which will be reported upon later in this book.

=General Results.= From these tests, the inspectors reached the unanimous conclusion that a paint made from any mixture of more than one white opaque pigment, either when used alone or in combination with small percentages of inert pigments, is far superior to any one single pigment paint. It was found that the straight white lead paints failed in every case, and this failure was so marked as to make it a conclusive demonstration of the unfitness of white lead along the Atlantic coast, when used without other pigments. Paints made with large percentages of white lead, however, gave excellent results.

Gypsum was found unsafe to use in any large proportion in a paint, because of its solubility and liability to percolate through the coating of linoxyn or dried film, thus destroying the surface of the paint.

Whiting, or calcium carbonate, demonstrated that it could be used in moderate percentage with some efficiency, but it was evident that any great excess of this pigment must also be avoided on account of its tendency towards rapid chalking. Magnesium silicate, aluminum silicate, and silica are three inert pigments which proved to be of great value in strengthening and reinforcing paints, especially when they were used in small percentage. In the same way, black fixe and barytes, or barium sulphate, also appeared to be useful in strengthening a paint. As these two last named pigments are chemically the same but physically different, the use of both in a paint formula is considered advantageous, because of the differences in size and form of their particles.

=Color Tests.= It was the unanimous conclusion of all the inspectors that panels of all formulas which were tinted either gray or yellow were showing far superior wear and less chalking and checking than those which were painted in plain white. The reinforcing action of the tinting materials must be credited for this lengthening of the wear of such paints. Formulas 5, 6, 9, and 16, for instance, in the gray, were in most excellent condition, and in these formulas were used ochre, umber, bone-black, carbon-black, Venetian red and other inert bases. On the yellow panels, formulas 5, 6, 9, and 16 were also in very superior condition, and in these formulas chrome yellow and inert pigments were also used.

Some of the color tests included the priming of boards with white lead, zinc oxide, sublimed white lead, lithopone, and other single pigment paints. Over these priming coats was placed a high grade brilliant paranitraniline red. Fairly good results were obtained in every case, but especially when lithopone or zinc oxide was used as a priming base.

These pigments seemed to have no effect upon the const.i.tution of the para red.

Prussian blue, a colored pigment largely used, but one liable to react with certain paint pigments, was admixed with various paints applied to certain panels. This color was found in some cases to have faded materially, especially when mixed with alkaline pigments such as white lead. Sublimed white lead and zinc oxide, which are more inert in nature, did not have such action on Prussian blue, and the tinted bases of these pigments stood up in a remarkable manner. The greens which were tested were all in very good condition, with absence of fading, and showing only slight mildew.

=Condensed Results of Inspection.= The results of inspection as obtained by the fence committee[20] having in charge the inspection of the test, have been condensed into table form, and are presented on pages 130-131.

[20] R. S. Perry, Director Scientific Section, Paint Manufacturers'

a.s.sociation of the U. S.; George Butler, Official Painter, representing Master House Painters' & Decorators' a.s.sociation, H.

A. Gardner, a.s.st. Director.

=Second Annual Inspection of the Atlantic City Test Fence.= After the original paints which had been applied to the Atlantic City Fence had been exposed for over two years, another inspection was made by a committee representing the Master Painters' a.s.sociation of Philadelphia and the Scientific Section of the Paint Manufacturers' a.s.sociation of the United States. A digest of the report of this committee[21] follows:

[21] George Butler, Official Painter Atlantic City Test Fence, representing Philadelphia Master Painters' a.s.sociation; Charles Macnichol, Master Painter; Henry A. Gardner, Director Scientific Section, Paint Manufacturers' a.s.sociation of the U. S.

"The painted panels were all carefully inspected by the inspectors in the usual manner. With the aid of high-power magnifying gla.s.ses, checking was determined. The degree of chalking exhibited by the various paints was ascertained by rubbing a piece of black cloth across the surface of each paint. Close observance was made to determine scaling, peeling, cracking, gloss, color, and the other factors to be considered when examining a painted surface. From these observations it was possible for the inspectors to state whether a panel exhibited general good condition, general fair condition, or general poor condition.

CHART OF RESULTS--FIRST INSPECTION--ATLANTIC CITY TEST FENCE

==============================+=================================+ Formula | INERT PIGMENTS | No. |---------------------------------| |Carbonate |Calcium | |Lead |Carbonate | | |Zinc | |Calcium | | |Oxide | |Sulphate | | | |Sublimed | | |Magnesium | | | |White | | |Silicate | | | |Lead | | | |Barium | | | | |Zinc | | | |Sulphate | | | | |Lead | | | | |Silica | | | | |White | | | | | |Blanc| | | | | | | | | | |Fixe | --+------+------+------+------+-----+-----+-----+----+----+-----+ | % | % | % | % | % | % | % | % | % | % | 1| 30.0 | 70.0 | | | | | | | | | 2| 50.0 | 50.0 | | | | | | | | | 3| 20.0 | 50.0 | 20.0 | |10.0 | | | | | | 4| 48.5 | 48.5 | | | 3.0 | | | | | | 5| 22.0 | 50.0 | | | 2.0 | |26.0 | | | | 6| | 64.0 | | | | | |36.0| | | 7| 37.0 | 63.0 | | | | | | | | | 8| 38.0 | 48.0 | | | | | | |14.0| | 9| | 73.0 | | | | | 2.0 | |25.0| | 10| 44.0 | 46.0 | | | 5.0 | | 5.0 | | | | 11| 50.0 | 50.0 | | | | | | | | | 12| 60.0 | 34.0 | | | 6% Inert Pigments | 13| | 27.0 | 60.0 | | 3.0 | |10.0 | | | | 14| 25.0 | 25.0 | 20.0 | | 5.0 |25.0 | | | | | 15| 20.0 | 40.0 | | 30.0 |10.0 | | | | | | 16| 33.0 | 33.0 | | | | | |34.0| | | 17| 40.0 | 40.0 | | | | | 3.0 |13.0| | 4.0 | 18| 75.0 | 25.0 | | | | | | | | | 19| | 25.0 | 75.0 | | | | | | | | 20| 67.0 | 19.5 | | |10.0 | | 3.5 | | | | 33| 15.0 | 30.0 | 25.0 | | | | | |30.0| | 34| 38.95| 33.58| 4.81| |19.48| | 3.18| | | | 35| 37.51| 25.87| 7.84| |20.36| | 8.42| | | | 36|100.0 | | | | | | | | | | 37|100.0 | | | | | | | | | | 38|100.0 | | | | | | | | | | 39| | | |100.0 | | | | | | | 40| | |100.0 | | | | | | | | 45| |100.0 | | | | | | | | | 46| | 61.0 | | | | | |39.0| | | 47| |100.0 | | | | | | | | | ==+======+======+======+======+=====+=====+=====+====+====+=====+

======================+==========+======+=========+======+ Formula |Panel |Hiding|Color |Hard- | No. |No. |Power | | ness | |First | |Condi-| | | | |Coat | | tion | | | | | |Second | | | | | | | |Coat | | | | | | | | |Third | | | | | | | | |Coat | | | | | | | | | |Aver-| | | | | | | | | | age | | | | | | --+---+----+----+-----+---+------+------+---------+------+ | | | | | | | | | | 1|610| 987| 664| 754| 1|Good |Good |Excellent| 8 | 2|913|1066| 948| 976| 3|Good |Good |Good | 5 | 3|912| 914| 786| 871| 5|Good |Fair |Good | 4 | 4|759| 939|1047| 915| 7|Good |Good |Good | 5 | 5|714|1000| 709| 808| 9|Good |Weak |Good | 8-1/2| 6|928|1189| 863| 993| 11|Fairly|Weak |Good | 8 | | | | | | |Good | | | | 7|763| 972| 891| 875| 13|Good |Good |Off Color| 7 | 8|786| 910| 767| 821| 15|Good |Good |Good | 8-1/2| 9|716|1081| 812| 870| 17|Fair |Poor |Good | 9 | 10|861|1014| 862| 912| 19|Good |Fair |Good | 5 | 11|822| 959| 918| 900| 21|Good |Good |Excellent| 7-1/2| 12|862| 965| 734| 854| 23|Good |Medium|Good | 4 | 13|916|1031|1121| 1073| 25|Good |Good |Good | 4 | 14|564| 806| 785| 718| 27|Bad |Medium|Good | 5 | 15|935|1044|1359| 1113| 29|Good |Medium|Good | 8-1/2| 16|799| 903| 994| 899| 31|Fair |Fair |Good | 7-1/2| 17|806|1016| 884| 902| 33|Good |Fair |Good | 4 | 18|788|1257| 973| 1006|145|Good |Good |Excellent| 3 | 19|700|1183|1400| 1094|147|Good |Good |Excellent| 2 | 20|776|1063| 877| 905|149|Good |Good |Good | 5 | 33|512| 836| 689| 679|176| |Fair | | | 34|523| 800| 810| 711|175|Good |Medium|Good | 4 | 35|450| 893| 724| 689|180|Good |Good |Good | 4 | 36|408| 711| 861| 660|181|Bad |Good |Good | 1 | 37|524|1065| 828| 806|182|Bad |Good |Good | 1 | 38|555| 888| 794| 746|177|Bad |Good |Good | 1 | 39|550| 941| 916| 802|178|Good |Fair |Good | 6 | 40|643| 810| 998| 817|168|Good |Good |Good | 2 | 45|850| | | |170|Fair |Fair |Good | 9 | 46|783| | | |169|Fair |Good |Good | 9 | 47|730| | | |172| |Good |Good |10 | ==+===+====+====+=====+===+======+======+=========+======+

==============+===========+===========+=============================== Formula | | | No. | | | |Checking |Chalking |Gloss |Remarks --+-----------+-----------+-----------+------------------------------- | | | | 1| |Very Slight|High |Like rubbed varnish work.

2|Hard Matt |Moderate |Med. High | 3| |Medium |Slight | 4| |Very Slight|Med. High | 5| |Slight |High |Hard surface.

6|Matt | |Good |Surface rough.

7| |Slight |High | 8| |Slight |High | 9|Heavy Matt |Medium |High |Peeling started.

10| |Some | Med. High | 11|Med. Matt |Some |Med. High |Some washing and discoloration.

12|Heavy Matt |Bad |Medium | 13| |Medium |Fair | 14|Evident |Some |Medium |Dead, spongy, surface. White | | | |incrustations.

15|Coa.r.s.e Matt|Slight |High | 16|Bad |Slight |Good |White incrustations.