Theatre Design & Technology - Summer 1983 - 28

considerably as Test # I indicates. Viscosity was chosen to produce uniformity
for the tests and because this is the primary mixing criterion employed by scenic artists. Depending upon the effect desired, a scenic artist will vary the viscosity of the paint; "thin and wet" (a small
quantity of pigment mixed into the size
water) for glazing, wet blending, puddling, etc., versus "thick and dry" for
backpainting and opaque drop techniques. Furthermore, as the weights of
the various pigments vary considerably
per volume, it was quite apparent that
should samples be mixed by weight a
much thicker paint would result using
Cobalt Blue than Emerald Green, thereby increasing the former's hiding capabilities. For all the tests the viscosity was
such that the paints would be suitable
for priming, base coating and overpainting, halfway between "thick" and "thin."
Having mixed the various colors, a
coverage test was undertaken with each
color to determine the quantity of paint
necessary to cover eight square feet of
primed canvas. Another identical test
was performed using paint without CabO-Sil added. In all but two instances
(Emerald Green and Hanover Green)
the amount of Cab-O-Sil-treated paint
necessary to cover eight square feet was
the same or less, with ten colors falling
into the laller category (Test #2). The
combined totals of all tests indicated a
17070 reduction in the amount of paint
expended.
Another test was undertaken to determine the hiding characteristics of
scene paints containing Cab-O-Sit. Four
stripes of deep color (Bulletin Red,

French Mineral Orange, Chrome Green
Medium, and American Ultramarine
Blue) were painted on flats, over which
the various scenic colors, with and without Cab-O-Sil were painted. The results
of these tests (Test #3) only favored the
Cab-O-Sil paints in one instance. The
tests did indicate, however, that colors
made with the addition of a considerable
amount of whiting or permanent white
would benefit by the addition of Cab-OSit. This result was confirmed later in
several instances where light pastel tints
were used for painting scenery.
A final set of tests was performed to
check Cab-O-Sil's ability to reduce pigment sellling, hard sedimentation deposits and to aid in redispersion. Seven
Imperial ounces of various scenic colors,
with and without Cab-O-Sil, were stored
in clear eight-Imperial-ounce bottles for
a three-month, a twelve-hour and a
thirty-minute period. Four samples of
each color were used for the various
time periods, which provided four sets
of results from each of the tests described below.
On the assumption that the differences between paints treated with and
without Cab-O-Sil would be most noticeable after the longest time period, the
three-month test was conducted first.
The first check using the three-month
samples was for sell ling. Because the
bOllles were calibrated along their sides
it was possible to note how far the pigment had settled towards the bottom of
the bottle. There was enough variation
in the samples to allow six definite steps
in gradation, along with + and - indications, resulting in sixteen positions on

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the scale_ (Although a very soft settling
[VS] rating was not used to designate
any of the colors in the three-month test,
it was included in anticipation of it being needed when the twelve-hour and
thirty-minute tests were conducted.)
When all four of the three-month
samples for each color had been checked
the results were compared. In every instance, three of the four ratings for each
color were identical, while the fourth did
not deviate more than a + or - gradation from the other three_ It was decided
that the rating which occurred three
times would be the norm for that color
and Test #4 illustrates these results. Colors that were given a very hard sellling
(VH) rating in the test had settled completely, while the top portion was perfectly clear. Samples rated soft settling
(S) had sell led somewhat but almost the
entire bottle still contained pigment and
only a small portion at the top was clear.
After completing the settling tests,
the hardness of the deposits was
checked. Of all the tests in this experiment, the hardness evaluation was the
most subjective. A plastic straw was
gently pushed to the bottom of the bottle and the tester noted the degree of resistance offered by the deposits. The
four samples for each color were
checked several times and the results
corresponded to those obtained from
the sellling test. Colors with heavy settling had hard deposits, while those with
less settling contained soft deposits. Because the hardness results were so subjective and because they added no new
information, the results are not charted
separately.
Finally the samples were checked for
redispersability. Each bottle was gently
turned over and righted again, this process continuing until all the pigment was
mixed into suspension, after which the
number of turns was recorded. Studying
the four figures for each color revealed
that most of the samples showed slight
variations, necessitating an averaging of
the results. After all the samples had
been averaged, they were compared with
the results obtained from the selliing
tests_ Except for Permanent White they
all corresponded most logically, the less
sell led deposits had redispersed more
easily than the heavily ettled colors.
Thus, the results of the settling and redispersion were grouped into a single set
of ratings (Tests #4 and #5).
comilll/ed

011

page 36

SITT /Summer 1983/Thealre Design & Technology

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