CRIMSON STARS.
Chlorate of potash 24 parts
Nitrate of strontia 32 „
Calomel 12 „
Sulphur 6 „
Shellac 6 „
Sulphide of copper 2 „
Charcoal (fine) 2 „
This composition gives a magnificent deep crimson when burnt _at night_.
Do not be disappointed, if, in your experiments _in the day-time_, the
colour should not appear very deep.
Remember that there are two kinds of colours in pyrotechny, and that
beyond a certain point it is impossible to amalgamate their respective
qualities. The first of these two kinds is the colour _which has a
considerable depth of tint, but which has not much reflective or
illuminative power_. The other kind is that _which has a very decided,
but not so deep, tint, and which is capable of surrounding itself with a
luminous atmosphere of colour during its combustion—in fact, which has
great brilliancy and power of illuminating objects_. Now the _last_ of
these two kinds is the proper one to be employed for star purposes. We
should never desire to produce a shower of dead-looking stars, however
intense their colour might be. It is also an ascertained fact that the
colour of stars always _appears deeper when seen from a distance_. Do
not then be disappointed, I repeat, if the colour appears somewhat weak
when you are making a trial of your composition _just under your eyes in
the day-time_.
Now, with regard to the crimson star composition above, remember that I
only say that it is one that succeeds _in my hands_. You may, perhaps,
think it too rapid in its combustion, in which case you can increase the
proportion of calomel, or decrease that of the chlorate of potash. The
calomel has the effect of deepening the colour, but at the same time of
retarding the combustion, and of weakening the illuminative power. The
shellac must be in as fine a powder as possible; it has the effect of
producing a rich, thick flame, and also of rendering more sulphur
unnecessary. It also enables the composition, after having been wetted
with the above fluid, to harden into a mass tolerably impervious to
moisture. The sulphide of copper is used for the purpose of giving a
very slight bluish tint to the flame, and thereby of neutralising any
yellow that might impair the purity of the crimson, arising from
impurity of the chemicals.
You should keep all these ingredients ready powdered, dried, and sifted
through your 40-mesh sifter; and then, when you require stars, you will
having nothing to do but to weigh out the proportions given in the
formula, and mix them on paper with a spatula. The more you handle the
nitrate of strontia, or any composition containing it, the moister it
will become, and the less effect it will produce. Therefore do not think
of mixing the ingredients till you are ready to make your stars, and
have a convenient, dry, warm place in which to stow them when made.
You can procure the things mentioned in the above receipt, and, in fact,
those required for all the coloured compositions, of Mr. Darby, 98,
Regent Street, Lambeth.
But, in case you may think it desirable to prepare and dry your nitrate
of strontia yourself, I give you the following directions—
Procure a common earthenware pipkin, or, still better, a glazed iron
frying-pan of a convenient size. Into this place your nitrate of
strontia in rough crystals. One or two pounds will be sufficient to
prepare at a time. Place the vessel on a clear fire, but do not make it
too hot. There is not the slightest danger of explosion, as this salt
cannot be induced to burn except in combination with other things. You
must now boil, or rather stew, the crystals in their own water of
crystallisation. The heat will soon cause them to run into a thick pulpy
mass. When in this state, they must be _constantly stirred_, or upon the
evaporation of the moisture they will resume a crystalline form. This
you wish particularly to avoid, as your object is to get this mass into
_powder_. Continue then to stir it with a stick or flat piece of wood
until the moisture is driven off by the heat, and the salt remains in
the condition of a white dry sand. A few trials will enable you to
perform this operation in such a manner that after it the strontia will
be ready at once for use. If, however, enough stirring did not take
place, you will find some fused lumps among your dry preparations; these
must be pounded in a mortar, and afterwards dried.
The operation described above is very simple, and does not take long to
perform. No strontia can be used for coloured stars or fires
_unprepared_. If, after keeping the dried nitrate of strontia for some
time, you find that it is again becoming moist, it may be re-dried,
either in the vessel used above, or in an open dish placed in a
well-heated oven. This operation is proper also for the preparation of
the nitrate of baryta.
For the solution of shellac you will find the following plan a
convenient one:—Make a very strong solution of the resin in methylated
spirit of wine, which shall be as thick as treacle. As you require your
thinner solution for moistening coloured star compositions, dilute a
portion of the thicker solution with the methylated spirit to the
strength required.
The sulphur used in all coloured compositions should be as free as
possible from acid; otherwise, when mixed with chlorate of potash, it
may be dangerous. If you have any doubt about it, wash the sulphur in a
solution of common potash in water, and dry it gradually. The acid will
be entirely neutralised by this plan. Never think of pounding sulphur
and chlorate of potash together; they form a detonating compound which
will explode with friction or percussion.
The compositions that I here give for colours are _perfectly safe_ when
made as I direct. I have made coloured stars from them, and placed these
stars at the side of a fireplace till they have become so hot that I
could not bear them in my hands, and I have subjected them to several
tests, all of which they have stood well; and I think I may safely
recommend them to you as not at all liable to spontaneous combustion or
possessed of any dangerous quality. I must tell you, however, that _they
may be heated till they explode_, but it is _quite unnecessary and very
foolish_ to expose them to any high temperature at all. In drying them,
a good plan is to put them in front of a fire in a flat tin box, which
will prevent any chance of their being ignited, and will at the same
time keep them in a thoroughly dry atmosphere till they become perfectly
hard. The box may be placed about two feet from the fire, so that it
becomes moderately warm.
In filling the pill-boxes with composition, put a piece of quick-match
through them, as directed above, and hold them by the two projecting
ends of match. Let a short groove be cut in the side of the stick with
which you press in the composition, large enough to allow it to pass the
quick-match without injuring it.