16. We now come to the very important subject of _coloured_ stars. These
require considerable care in their preparation, the beauty of their
performance depending entirely upon the _uniform fineness, the intimate
union, and the dryness of their ingredients_. If you wish to make these
coloured stars with any degree of satisfaction to yourself, keep the
various preparations which enter into their composition _always ready
for use_—that is, _in fine dry powder_, preserved in well-corked or
stoppered bottles. There is one chemical salt which requires especial
care in keeping, on account of its deliquescent properties—that is, of
its tendency to attract moisture from the air; and unless this salt,
which is _the nitrate of strontia_, be thoroughly free from moisture
when used, it will produce no effect at all, except a needless waste of
chemicals. I must therefore tell you that the formulas which I am about
to give you will fail most entirely in your hands, unless you are very
particular in this matter of dryness. Over and over again have I been
led to condemn formulas for coloured stars and fires as useless or
imperfect, for the sole reason that I did not then know how their
ingredients were to be handled, and what care was necessary for the
production of their intended effect.
In the first place I strongly recommend you to attempt to make no
coloured stars _for rockets, except such as are made in the pill-box
cases_, of which I have spoken before. These pill-boxes are made in the
following manner:—Procure a piece of _straight_ iron rod, 12 inches
long, and from three-eighths to half-an-inch in size; the usual size for
this “former” is about seven-sixteenths of an inch. Now cut some
cartridge paper into strips about 8 inches wide, and from 9 to 10 inches
long; paste these strips all over, and roll them round the iron rod
closely and neatly. When this is done, remove the case thus formed from
the rod without tearing or breaking it, and set it aside to dry. When
dry it will be very hard and stiff. It can then be cut, by means of a
very sharp knife, into little lengths of half-an-inch each. These
lengths are the open pill-boxes, into which your composition is to be
rammed for _coloured rocket stars_.
In order to accomplish the filling of these cases with the least amount
of trouble, procure a piece of stick, of a convenient length, and of
such a size round that it will pass _easily_ into the pill-boxes. Next
take a small piece of quick-match, about 1½ inch long, and pass it
through the pill-box in such a manner that it may project beyond each
end about half-an-inch (see Fig. 31). You will be able to steady the
pill-box while filling it by holding it by these two ends of
quick-match. The composition pressed into these boxes is always slightly
moistened; and by this means, when once dry, will not be liable to be
shaken out again. In making, however, any trials of your coloured star
compositions _for your own satisfaction_ before making a large batch of
stars, you had better press the composition in _dry_; by this means you
will be able to see at once what their performance is worth.
[Illustration:
Fig. 31.
]
The fluid that I employ for moistening these coloured compositions is a
solution of shellac in methylated spirits of wine. As shellac enters
into the composition of many of these colours, it will not be necessary
to make your solution a strong one. It should be of the thickness of the
ordinary spirit varnishes, such as photographers use for coating their
negative pictures. The exact strength is not a matter of any great
importance, as long as you do not make the solution too rich in shellac;
for by doing this you will impair the purity of your colour to some
extent.
Remember that you must make these compositions _wet_. A very slight
moistening is sufficient to make them _bind_ well when pressed into
their cases.
The first colour of which I shall speak will be the red, or crimson. It
is in the preparation of this colour that you must be most careful about
_dryness_.