19. Our next colour will be the green. I have especially observed that
stars of this colour always appear far more intense when burning at a
distance than when close to the spectator. The colour produced by the
nitrate of baryta is never very deep where any great rapidity of
combustion is required. It is, however, an exceedingly pretty tint, and
is seen to its greatest advantage when used in contrast with a rich red.
I employ the following formula for
GREEN ROCKET STARS.
No. 3.
Chlorate of potash 20 parts.
Nitrate of baryta 40 „
Calomel 10 „
Sulphur 8 „
Shellac 3 „
Charcoal (fine) 1 part.
Sulphide of copper 1 „
The composition made according to this formula will produce a colour
which leaves nothing to be desired, if the several ingredients be only
_in fine powder, dry, and pure_. It is not affected by moisture nearly
so much as any composition containing nitrate of strontia. The shellac
employed should be as fine as possible. And here let me remark that the
reduction of shellac to powder is a process of itself; no
coarsely-powdered shellac will answer your purpose. Mr. Darby will
supply you with it in _fine_ powder quite as cheaply as you can get it
done elsewhere. Composition No. 3 is to be moistened with the solution
of shellac. The sulphide of copper you may have some difficulty in
procuring. You are sure, however, to meet with it at the shop of Messrs.
Bolton and Co., 146, Holborn-Bars, London, but you must ask for the
_fused_ sulphide of copper, for there is a _precipitated_ sulphide also,
which is of no use to you. Do not use any of it that will not pass
through your 40-mesh sifter. I add this ingredient rather as an
improvement than as necessary to the composition. You may substitute for
it, if you please, the preparation of copper which I am about to
recommend in the composition for blue stars. If composition No. 3 should
be thought too fierce, try the addition of a little more calomel.