Evening star., 1943-09-08
American Tank Crews
Use CoIored Smokes
10 Guide Own Pilots
Special Dispatch to The Star


WILMINGTON. Del. - Rainbow
coiored smokes which puff out from
tiny cannisters in red. orange, yell
low. green and violet hues now en-
soie American tanks and other
eround vehicles in the battle zones
70 operate with greater freedom in
areas OF intense air activity without
oanger from attack by their own
planes.
The need for simple yet reliable
identification of ground forces was
recognized as early as the last war,
wnen military movements were rela-
lively slow and aerial warfare was
m its infancy. With the swift
moving tanks of this war, supported
py squadrons of planes, this need
becomes imperative, as evinced by
the savage attack on German tank
division in North Africa a few
months ago by Nazi dive bombers.
The Germans, from their high alti-
tude, thought they were attacking
British tanks.
Marking Served as Target.
Even before our entrance into the
war, military authorities gave at
tention to the problem of identifying
ground units from the air. One
proposed solution was to paint a
distinctive design in white or yellow
on the top or side of the tank or
other vehicle, but tests demonstrated
such designs made perfect targets
for enemy bombing planes. Accord
ing to Brig. Gen Alden H. Watt.
writing in the Infantry Journal, "It
was obvious that there would be
more danger in using this system of
identification than there would be
in leaving the tank unpainted and
taking chance that it would be
bombed by its own airplanes as well
as the enemy's."
Other schemes were proposed
signal flags, flares, smoke pots-but
none proved successful 1t was then
suggested that colored smokes might
solve the problem. However, no
practical colored smokes were avail
able, nor was any development work
under way on this phase of the prob
lem.
1t was at this stage that Du Pont
dye experts were called in to assist
the Chemical Warfare Service. The
specifications were rigid. 1t was
necessary to have sufficient num-
Der OF colors to permit numerous
code variations. The colors had to be
brilliant, for ease of visibility at
high attitudes. They had to be
dense, so that the necessary amount
could be packed into a small can
mister. They had to be absolutely
uniform. And f1nally-the most diff
fcult of all-they had to be sufi-
ciently stable to Withstand rela-
lively high temperatures.
This was necessary because the
most promising scheme involved
evaporating a cloud of dyestuff par
t1cles by means of the heat lib
Grated from a suitable burning
charge In canister, the dye being
placed in the canister along with
the charge.
Problem Proved Difficult.
Meeting the last-named specifica-
tion proved to be an even more diff
cult job than anticipated, since
the heat from the burning charge
IN the canister is sufficient to break
down any organic dyestuff and de-
stroy its color. 1t was necessary not
only TO find the most heat-resistant
collors possible, but also to work out
q methd for evaporating the dyes In
such a way that they would not be
destroyed by the high temperature
Of the burning charge.
Finally, after literally hundreds of
compounds had been tested, a Sc
ries of suitable eolors was found,
and technique worked out for their
Use. Before leaving for Africa, 1t.
Gen. George Patton had a number
OF his officers go to Edgewood Ar
senal to see tests of these new col
ored smokes under conditions simu-
lating battle practice The results
were SO impressive that he ordered
several thousand cannisters to be
made up as soon as possible, and
when his force embarked for Africa
1T carried plentiful supply Of this
ACW 4AC-odSuiS u1uiHbIUfI.
One form of the finished prod
net is a small canister, about the
same size and shape as standard
hand grenatde, which gives of any
one of five brilliant and distinct
colors-red, orange, yellow, green
and violet-in addition to black and
white. The dyes used for this pur-
pose include several of the anthra-
quinone type, similar to those used
for dyeing textiles and paper.
If the driver of tank has to iden-
tify himself, he simply pulls the pin
and throws out one or more cannis-
ters. The colored smoke begins
coming off in three or four seconds
and lasts for about three minutes.
which is sufficient to permit identi-
fication by friendly aircraft. Tests
have shown that it is possible to tell
colors apart from height of around
2 miles without difficulty.