The Chemistry of Powder and Explosives - Sciencemadness Dot Org

122 PYROTECHNICS
the finished product up with a little stearine before forming into
pellets." The present writer has found that the substitution of
/?-naphthol for naphthol pitch yields fairly good snakes which,
however, are not so long and not so shiny, and are blacker and
covered with wartlike protuberances.
Smokes
Smoke shells and rockets are used to produce smoke clouds for
military signaling and, in daylight fireworks, for ornamental
effects. The shell ca>se or rocket head is filled with a fine powder
of the desired color, which powdered material need not necessarily
be one which will tolerate heat, and this is dispersed in
the form of a colored cloud by the explosion of a small bag of
gunpowder placed as near to its center as may be. Artificial
vermilion (red), ultramarine (blue), Paris green, chrome yellow,
chalk, and ivory black are among the materials which
have been used, but almost any material which has a bright
color when powdered and which does not cake together may be
employed.
Colored smokes strictly so called are produced by the burning,
in smoke pots or smoke cases, of pyrotechnic compositions which
contain colored substances capable of being sublimed without an
undue amount of decomposition. The substances are volatilized
by the heat of the burning compositions to form colored vapors
which quickly condense to form clouds of finely divided colored
dust. Colored smokes are used for military signaling, and recently
have found use in colored moving pictures. Red smokes, for example,
were used in the "Wizard of Oz." Colored smoke compositions
are commonly rammed lightly, not packed firmly, in cases,
say 1 inch in internal diameter and 4 inches long, both ends of
which are closed with plugs of clay or wood. Holes, y± inch in
diameter, are bored through the case at intervals on a spiral line
around it; the topmost hole penetrates well into the composition
and is filled with starting fire material into which a piece of
black match, held in place by meal powder paste, is inserted.
According to Faber, 57 the following-listed compositions were used
in American airplane smoke-signal grenades during the first
World War.
57 Op. tit., Vol. 1, p. 219.