27. Fireworks of this species are exceedingly beautiful and effective,
especially when made with coloured stars, and fired in numbers. Their
manufacture is somewhat difficult, but the difficulty is one well worth
overcoming. I made a considerable series of experiments before I
produced a Roman candle that answered my expectations. At last, however,
I hit upon a plan which has never since failed in my hands, and I think
that, if I can succeed in making my meaning understood, and you will
undertake to follow my directions closely, you will find my plan a good
one.
There are several conditions upon which success depends, and which it
will be as well to enumerate. A poor Roman candle is not worth making.
If you wish to produce one that will satisfy you, remember—
1st.—That you must have a composition to burn in the intervals between
the stars, which will produce as good an effect when the Roman candle is
almost spent as when first lighted—in fact, which will throw a jet of
fire uniformly good throughout.
2nd.—That your stars must be hard enough to resist the pressure of the
drift with which you consolidate the composition.
3rd.—That the stars must be of tolerably rapid combustion, otherwise
they will not be ignited before they are blown into the air.
4th.—That the charges of powder for blowing the stars must be regulated
to a great nicety. If too small, they will not throw them high enough;
if too large, they may burst the case, or spoil the intended effect of
the stars, or so disturb the composition below them that three or four
of the stars will be fired in rapid succession, or almost
instantaneously.
Now, the first thing to be considered is the size of which Roman candles
are to be made. I make them of _one_ size only, for I have found that it
is much more convenient to have but one size of stars to prepare, and
one size of cases to roll, and one scale of powder-charge to remember,
than to run the risk of confusion by having to think of various sizes.
Besides, all the effect that these pieces are capable of can be produced
by my one size. This size is _that called the 2-oz. Roman candle_. The
former for the cases must be five-eighths of an inch in diameter, and
should be 18 inches long.
These fireworks require rather a large amount of paper and imperial
board for the manufacture of their cases. A good stout case may be made
as follows:—Cut your sheets of 70-lb. brown paper into halves, and your
sheets of imperial board into six equal pieces. One of these pieces,
with one half-sheet of 70-lb. paper, will make one case. Paste your
pieces of imperial board _all over_, as well as the sheets of paper. Rub
some paste on your former, and proceed to roll a piece of the pasted
board tightly and smoothly round the former till all but about two
inches of it is rolled. Then take the pasted half-sheet of brown paper,
and roll this upon the imperial board in the manner described for making
golden rain cases. The method there given is of especial value when the
cases that you are making are of considerable length, because it enables
you to roll the paper and board very straightly, which cannot be done so
easily by any other means that I know of. The cases thus made will be
pasted throughout and can be easily removed from off the former. They
will be about 14 inches long, which is a very good size. You can, of
course, make them shorter for experiments, but you will find the above
size not too large for exhibition purposes. I do not think it will do to
make the cases very much thinner than I have directed, but a few
experiments will decide what length or thickness of case succeeds best
in your hands. I have given you my size, which I have no wish to alter.
Now the next thing to be done is to prepare the stars. These are made in
a tubular mould, the exact size of which I have sketched in the page of
illustrations, Fig. 37. But before giving you directions for making
these stars, I may as well furnish you with a few formulas for their
composition.