THE SCOPE OF PRACTICAL PAINT TESTS
=The Pigment Contention.= During the year 1906 officials of the North
Dakota Agricultural Experiment Station examined a number of paints on
sale in the northwestern States. The presence of large quantities of
inert pigments as well as water, in some of these paints, prompted
agitation for State laws requiring the formula-labeling of paints.
Certain paints made of white opaque pigments such as white lead and zinc
oxide were exempted from the statute. The white opaque pigments used in
these paints were believed by certain manufacturers as well as by many
prominent paint authorities of high standing to be benefited in their
wearing value by the addition of small percentages of inert crystalline
pigments, such as barytes, silica, China clay, etc. Laboratory
experiments had already determined that these inert crystalline pigments
had a certain definite action in increasing the life of paints, but it
had become evident that they should be used with discretion, in
moderation, and with a proper understanding of their limitations, if the
best results were to be obtained. The addition of very large quantities
of such pigments was not indulged in by discriminating manufacturers,
but the exact percentage to use was a matter of great doubt, even to the
most experienced. In order to determine just what percentage of
crystalline pigments, admixed with white opaque paint pigments, would
give the best service and results, it seemed imperative that practical
paint tests should be made. A series of paint tests on commercial brands
of paint had already been started at the Fargo Agricultural College,
and, at the suggestion of the Paint Manufacturers' Association of the
United States, another series of practical paint tests were instituted,
and carried out under the supervision of Dr. E. F. Ladd, Director of the
North Dakota Experiment Station.
=Test Fences to Solve the Problem.= It was apparent that the pigment
question could be solved only through field tests made on a
comprehensive basis and placed under the control of scientific and
technical societies of renown, so that they might be fair and unbiased
from every standpoint. In order to secure a comparison of the wearing of
different paint formulas in various sections of the country and under
differing climatic conditions, another series of tests was started in
the East soon after the North Dakota tests had been started.
Simultaneously fences were erected at Atlantic City, N. J., and
Pittsburg, Pa. The site of the Atlantic City fence is a strip of land
running due north from Atlantic and Savannah Avenues and within a short
distance from the Atlantic Ocean, the exposure being a severe one. The
site of the Pittsburg fence is back of the athletic field of the
Carnegie Technical Schools, the fence running east and west and being
exposed to the heavily charged sooty atmosphere coming from the many
industrial plants near by.
=Construction of Framework of Fences.= At these two locations framework
fences were built, upon which were placed a series of painted panels.
Heavy yellow pine posts six inches square were set in the ground about
six feet apart and to the depth of about four feet, upon a concrete
base. The posts were solidly tamped and then braced at the top with
supplementary studding braces two inches thick. Connecting the posts was
a line of studding six inches by two inches, forming a solid framework,
the bottom of which was approximately fifteen inches from the ground.
The bottoms and tops of the fences were protected by heavy boards two
inches thick, so that the moisture and rain might be prevented from
working itself up into the wood. The whole fence was sheathed with
twelve-inch planed white pine, thus forming a solid background for the
test panels.
=Lumber for Panels.= The lumber for the test panels was most carefully
selected, being of three grades--white pine, yellow pine, and cypress. A
large amount of each grade of lumber was secured, and after the best
portion had been made up into panels, the panels were inspected by an
expert lumber classer; nearly 40% being rejected on account of the
presence of knots or sappy places which appeared upon the surface. Each
of the panels finally passed upon as suitable for the test was branded
with a hot iron with consecutive numbers running from 1 to 186. The
grade of wood used for each panel was indicated by an abbreviated
mark--W for white pine, C for cypress, and Y for yellow pine. In order
that a record of each panel might be kept on file, previous to the
application of paint to the panels, a complete series of photographs was
taken of the panels in sets of four. This work seemed advisable so that
the future failure of paint on any one panel, which might be thought due
to faulty wood, could be either verified or refuted by a reference to
the series of photographs made of the bare panels.
[Illustration: View of Atlantic City Test Fence]
=Construction of Panels.= The panels were constructed of Dutch weather
boarding, tongued and grooved together in strips of three pieces and
capped at the top with a weather strip, forming a finished surface three
feet long and fifteen and a half inches high. They were firmly braced
together at their backs and nailed in such a manner that no portion of
the nails would appear on the surface of the panel, thus preventing the
staining of the panel from rust. The construction of the framework of
the fences at Atlantic City and Pittsburg was of such a nature that they
would each accommodate 560 panels of this type.
=Starting of Tests.= On account of the lateness of the season, it was
found necessary to do the painting of the tests within a building, so
that each formula might be subjected to fair and equal conditions of
application, thus excluding the blowing of dust or rain upon the painted
surfaces, which would have taken place had the panels been painted upon
the fence. The painting of the panels began in January, 1908, the
temperature within the buildings in which the work was done averaging 50
degrees Fahrenheit throughout the work.
It was decided to test each formula in three colors, in duplicate, and
on each grade of wood, exposing the duplicates on either side of the
fence. Thus for one paint formula there were required 18 panels, or 6
painted in each color and on 3 grades of wood.
=Paints for Tests.= The mixed paints received for the tests were in
quart cans, having been especially prepared from the formulas submitted
to manufacturers by the technical committee in charge of the work. They
were properly labeled with their number and color, in each case. The
formulas decided upon for the test are described later. The various
white leads and other single pigment paints which were used were
received in kegs weighing 12-1/2 pounds each, having been bought in the
open market and then given a formula number. The formulas of the paints
designed for both the Atlantic City and Pittsburg tests, as well as the
numbers of the panels upon which the paints were applied, are shown on
pages 131-133-145. The analysis of one of the combination paints applied
is herewith given, to show the correct method of stating the composition
of a paint.
FORMULA NO. 20, ATLANTIC CITY TEST FENCE
Percentage Composition
===================+=======+=======+=======+=======
|Pigment|Vehicle| Total |
-------------------+-------+-------+-------+-------
Corroded white lead| 67.01 | -- | 42.84 |
Zinc oxide | 19.89 | -- | 12.71 |
Asbestine | 3.86 | -- | 2.47 |
Calcium carbonate | 9.24 | -- | 5.91 |
Raw oil | -- | 94.30 | 34.02 |
Japan drier | -- | 3.89 | 1.40 |
Turpentine | -- | 1.81 | 0.65 |
-------------------+-------+-------+-------+-------
|100.00 |100.00 |100.00 |
===================+=======+=======+=======+=======
=Brushes.= Heavy 7-O round bristle brushes were used for the priming
coat so that the paint might be well worked into the wood, while for the
second and third coats three-inch chisel edge brushes were used. These
brushes were, of course, washed several times with turpentine after
painting each panel, so that pigments from one paint could not be
carried over into a paint containing other pigments.
[Illustration: Cypress Panels]
=Shellacking Panels.= The shellacking of any bad places of minor nature
which may have been present on the surfaces of some of the panels, was
done with the highest grade orange shellac. It was thought advisable to
determine whether shellacking over the priming coat of paint or on the
bare wood previous to the application of the priming coat, was the
better method. Panels Nos. 1 to 8 in each test were therefore shellacked
over the priming coat, while on all other panels the shellacking was
done directly on the bare wood previous to the application of the
priming coat of paint.
=Application of Paints.= In order to determine just how much paint was
applied to each panel and to reckon the spreading rate therefrom,
careful weighings were made during the application of every paint. This
was carried out by placing a quart can of paint as received, upon a
laboratory balance, the gross weight being taken and recorded. The can
was shaken and its contents transferred to a quart-size enameled cup
where with the aid of a paddle it was broken up into a mixture of even
consistency. A portion of this paint was then transferred to two small
sample cans carefully numbered with the formula number, for future
reference and analysis. The reduction of the paint was then made. The
brush used on the priming coat was placed with the pot and the paint on
the balance and the weight taken by the official weigher. The pot was
then given to the painter who applied the priming coat to one panel. The
brush, pot, and paint were then handed back to the official weigher and
the difference in weight recorded. From these data could be reckoned the
spreading rate of the formula applied.
The drying of the panels was noted every few hours and observations made
to determine whether the paints were penetrating properly into the
surface of the wood. A period of eight days was allowed between each
coat in order that thoroughly hard setting might take place.
During the application of the second coat of paint to the panels, fresh
cans of paint were used in every case so that fresh reductions could be
made of the proper consistency. Full data were also recorded on the ease
of application, working, and nature of drying shown, as well as
appearance presented by each paint after each coat had been applied. New
packages of paint were also used for the third coat, and, as a rule, the
paint was applied without reduction or with full oil reduction,
turpentine being eliminated in nearly every case for the third coat
work.
=Reductions.= The single pigment paints, such as white leads, were
reduced by the so-called ounce system, each ounce of oil added to 12-1/2
ounces of paste pigment representing one gallon of vehicle to one
hundred pounds of lead. A complete report of the reductions, spreading
rates, etc., used in the tests would take up three or four hundred pages
of printed matter. The reductions shown on the following formulas are,
however, fairly representative of the reductions used on the combination
and single pigment paints.
REDUCTIONS ON FORMULA NO. 2
_White and Yellow_
1st Coat Condition when opened--good. Consistency when broken
up--heavy. Reduction recommended by manufacturer--none. Reduction
used--3 pints raw oil, 1 pint turps, 1 gallon paint. Consistency after
reducing--good, stiff. Working--fair. Drying--fair on pines;
cypress--poor. Penetration, pines--good; cypress--poor.
2nd Coat Consistency when broken up--heavy. Reduction used--1-1/2
pints turpentine, 1 pint boiled oil. Consistency after reducing--good.
Working--good. Hiding--medium. Drying on pines--good; cypress--poor.
One-half pint japan added to gallon of paint. Penetration--fair.
3rd Coat Reduction used--1-1/2 pints oil, 1/2 pint turpentine.
_Reductions for Lead Pastes_ Calculated on 100 lb. keg.
Formulas Nos. 37-38. (Corroded White Lead.)
1st Coat 6-1/2 gallons oil, 1/2 gallon turpentine, 1 pint turpentine
japan.
2nd Coat 3-1/2 gallons oil, 1 gallon turpentine, 1 pint japan.
3rd Coat 3 gallons oil, 1 pint turpentine, 1/2 pint japan.
=Hiding Power of Paints.= When the priming coat had thoroughly dried on
each panel, the painter carefully stencilled a black Geneva cross over
the priming coat with lampblack in oil. The object of this black cross
was to make a determination of the comparative opacity or hiding power
of the different paints applied. It is well known that various pigments
when ground in oil differ in their hiding power in direct proportion to
the difference in the refractive indices of the pigments and oils used,
those containing high percentages of pigments such as white lead and
zinc oxide being superior in hiding power. After the second and third
coat of paint had been applied to each panel, there was evident a
remarkable difference in the hiding power, as the black cross showed
through in some cases quite clearly, while in other cases it was almost
completely hidden. The hiding power of a paint is one of the properties
which the master painter looks upon as most essential, but it should, of
course, be accompanied in a satisfactory paint by good spreading power
and longevity.
=Actinic Light Tests.= After the drying of all the paints, it was
decided that it would be of extreme interest to conduct a test on the
resistance of certain paints to actinic light. It is well known that the
ultraviolet or chemical rays of the sun are most energetic in causing
chemical reactions that result in the early decay of certain types of
paint. It was thought that the disintegrating effect of these rays, as
well as their effect in the bleaching out of colors, might be prevented
by placing upon certain panels small orange colored glass slides which
would prevent the passing of these rays to the painted surface. The
slides used were five inches long and three inches wide and were placed
upon the middle board of certain panels, with picture framing, putty,
and galvanized iron tacks. The preservation of the underlying surface
from the sun's rays would, it was thought, prevent the deterioration of
the paint, and at the same time preserve its original color so that it
might be compared to the color of the exposed portion at the time of
inspection.
=Supervision of Tests.= The Atlantic City tests were under the constant
supervision of Committee E of the American Society for Testing
Materials, this committee having accepted the inspection of the fence. A
representative was constantly present throughout the work in order to
see that each formula received fair treatment. The actual painting work
was under the supervision of the writer, together with a master painter
representing George Butler who was chosen by the Master Painters'
Association of Philadelphia as the official painter of the Atlantic
City test fence. Mr. J. B. Campbell of Chicago also acted as an official
of the Paint Manufacturers' Association in the application of the
formulas to both the Atlantic City and Pittsburg fences.
At Pittsburg the fence was placed directly under the supervision and
control of the Carnegie Technical Schools, who chose for the fence work
a committee of their technical force. Drs. James and Schaeffer of this
institution were present throughout most of the work and were constantly
represented during the test. The Pittsburg Master Painters' Association
appointed a committee consisting of Messrs. Dewar, Rapp, and Cluley, for
the actual painting work, and they were represented with the writer
throughout the tests.
Great interest was exhibited in the work by the committees in charge,
and the skill of the practical painters, combined with the care of the
inspectors, made the treatment of each formula fair and satisfactory.