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' Association of Pennsylvania, the Scientific Section of the
Paint Manufacturers' Association 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 assembled 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.
[Illustration: Series of Black Felt Cloths used in making the Chalk
Tests on the Various Formulas. Numbers over Cloths represent Panels]
[Illustration: CHALKING.--Type of Decay Exhibited by Improperly Made
Paint (magnified view)]
[Illustration: CHECKING.--Type of Decay Exhibited by Improperly Made
Paint (magnified view)]
[Illustration: BLISTERING.--Type of Decay Exhibited by Improperly Made
Paint (magnified view)]
[Illustration: CRACKING.--Type of Decay Exhibited by Improperly Made
Paint (magnified view)]
[Illustration: GENERAL DISINTEGRATION.--Type of Decay Exhibited by
Improperly Made Paint (magnified view)]
[Illustration: 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 glass magnifying fifteen diameters. It is well
known that examinations with such a hand glass 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.