The Calumet news. [volume] (Calumet, Mich.) 1907-1938, 1913-11-20

no attention being paid To their per
manerCy. The natural result was coll
ors that were notorious for fading. At
! chat time little was known of any
systematic method of testing for per
maucnCy, and when | undertook to Sc
cure standards that were permanent [
had To devise methods.
The deterioration of colors is caused
by the action of both light and atmos-
! phcrc Chemical composition will give
Il clu" as To the action of atmosphere.
but the action of light is more subtle
and nothing short of an actual test il
of value. OF course, it is impractical
bic To have a test extending over
Years of time 50 some method had to
hC devised To give results i'm days
1t has been determined from cx-
haustivc experiments that a color that
will not change after exposure to
bright sunlight in the summer for Il
period of three days can be relied up
On To withstand days of exposure in
the diltused light of an ordinary ruuu
! The amount Of aCtiuiC light given Off
by the sun during a cloudless day i'm
/ summer was measured photographed
| ~, and 10y the same method the
amount can be gaugcd ON IA cloudy or
rainy day. This enabled IA standard
condition to he measured and gov
erned.
The amount of fading In such day.
even with rather fugitive Colors. is
very slight, 50 the following method
was devised to determine what effect
! long exposure would have a strip Of
Ipapcr printed with an ink made from
| the color was exposed To light one,
two and three days, with a part pro-
tectcd 10y black paper. BY compari
son of the exposed parts with that pro-
tccted 10y black paper it was found
that some of the colors would fade u
little more each day, and others would
fade for the first day. and remain
stable for the other two days. The
former were classed as progressive in
fading. and the inference is that they
would eventually fade away. The as
sumption is that the others would fade
slightly and then remain permanent.
Further experience has corroboratcd
this view. and today no Colors are
used in the bureau that show progress
siyo fadnEs
We now make fading tests with an
artificial lght--thc quarts mercury
lamp-which is on the same principle
as the familiar Coopcr-U Hewitt mer-
curry tube. except il is so high in the
ultraviolet. or actinic rays. that IL is
enclosed in - special protective casing
To prevent those near IL from being
sunburned which would he the ease
If they were exposed To il for few
minutes
In securing permanent colors. We
had To- sacrifice some of the brillaney
that is characteristic of nearly all the
.anilinc colors, although there is solid
ity and softncss that is more artistic
in orr present series
The only ailine Colors we use are
the reds and those colOrs that contain
red purples and browns and Gran
gcsD. For yellow we use chrome yell
low, for blue prussian blue aud III
tramaIiue. and for black we use bone
black, which Is practically carbon All
of these are minerals except prussian
blue, which is partly organic and part
w inorganic
The source of some of these cOlorS
may he of interest to YOU The ami
line reds are made from coal tar; the
prussian blue was originally made
from calcined horn. but il is now made
from great variety of substance.
and can even be made extraordinarily
from the nitrogen of the air: the ul-
tramariue was originally made from
lapis lazuli, but now synthetcally by
calcinine its constituents; the chrome
yellow is made artificially and iS
chemically chromate of lead. The
boneblaCk is made from calcined
bones. as it's name would Indicate.
The science of color, which has ad-
Vanced to n rational stage only In re-
cent years. is too complex to be treat
ed at length here, but there are few
phenomena that may be of interest to
you. An ink is not "a simple color, and
II shows two distinct hues, known as
overtone and undertone. These may
be simply defined as the color trans
mitted from the surface. or reflected,
and that transmitted through the ink.
An appreciable thickness of the ink
Continued on 5th Paaa4- 2nd colnnn.---