TkSTS ON THE COLOR FASTNESS TO LIGHT OF DYED TEXTILES
E. R. Pierce
January 3, 1943
TESTS ON THE COLOR FASTNESS TO LIGHT OF DYED TKXTILLS
When an engineer wants to measure the strength of a
steel column it is a comparatively simple matter to put
the column in a press and measure the load it will carry
in pounds per square inch. When the weight of some object
is desired it is easy to weigh the object and obtain an
answer in pounds. Volumes, specific gravities, and den-
sities may be determined in the same ivay. All of these
physical properties are clearly defined and measurable.
Consider, on the other hand, the fading properties of
dyed cloth. There is no means by which the amount a
specimen of cloth has faded can be measured. To overcome
this difficulty the Research Committee of the American
Association of Textile Chemists and Colorists began a few
years ago to set up a series of standards, a series of
cloths whose fastness to light was known and to which
other samples of cloth could be compared. For example,
if a certain sample is to be tested it is exposed to
strong light for a given period of time, and then compered
with a standard of similar quality which had been exposed
for the same period of time. If the new sample has faded
more than the standard, it fails the test; if it has faded
less than the standard it passes the test. If a oloth is
to be classified according to its fastness to light, it
will be exposed for a given length of time and then com-
pared with several different grades of cloth, each exposed
for the same length of time under the same conditions.
Suppose the sample faded more than grade 5, but less than
grade 4j that sample would be classified as between 4 and
5 on the standard color fastness-to -light scale*
In order to Institute such a system, suitable standards
had to be chosen and different length tests made on them.
This was done at the National Bureau of Standards, where
1 was employed by the American Association of Textile
Chemists and Colonists during the summer of 1940. Eight
samples of cloth of different fastness to light were chosen,
each to be put through tests varying in length from 1 hour
to 768 hours* Sample No. 1 showed distinct signs of fading
after two hours, and was nearly white after forty eight
hours, while sample No. 8 didn't begin to show any signs
of fading until after 192 hours and had faded very slightly
at the end of the test.
Similar tests were run using natural sunlight and art-
ificial light from a Fadeometer. Samples exposed to sun-
light were displayed on the roof of the Bureau, on dry,
bright days only, between the hours of 9 and 3 o'clock.
In exposing the samples half of the cloth was covered up
in order that the faded cloth could easily be compared
with its original color. 768 hour tests run at the rate
of 6 hours a day, on bright days only, of course took a '
great length of time. To overcome this difficulty a
machine called a Fadeometer was used. It consisted merely
of a carbon arc lamp around which samples could be hung in
small metal frames a constant distance, about 14 inches,
from the arc. The humidity inside the machine was kept
constantly high. Cloth fades much faster in wet atmosphere.
This machine would run 20 hours on one set of electrodes,
and by running it all night tests were much faster than
by the natural sunlight method.
At the end of the summer both tests had been completed
and the samples mounted and filed in the proper order.
The war has of course slowed down such research, but one
of the most interesting and untouched experimental fields
lies in the development of tests for color fastness to light
of dyed textiles.