39. These are certainly among the most beautiful and effective pieces to
be met with in the whole range of pyrotechny. They should find a place
in every exhibition, and, if only prepared properly, according to the
directions which I am now about to give, will be sure to prove one of
the most striking features in your display.
They have one great advantage—that there is no limit to the modes of
combination or arrangement in which these pieces may be effectively
employed. By means of them you can make any such things as the
following:—Fountains of any size or design, cascades, brilliant suns,
either fixed or revolving; bouquets of Chinese fire, Prince of Wales’s
feathers, trees of silver flowers, and a thousand other devices which
will readily occur to you.
But, like many other things which are possessed of highly useful or
ornamental qualities, they have a corresponding disadvantage. Their
compositions, to produce the desired effect, must be made _as shortly as
possible before you intend_ to fire them; for the ingredients upon which
they rely for their beauty are _filings of steel for brilliant fires_,
and _borings of iron for Chinese fires_, and unless these filings and
borings be entirely free from rust at the time when they are fired, the
effect produced will be insignificant as compared with what it should
be. And it must be borne in mind that both iron and steel become very
soon and very easily corroded when mixed with any composition into which
nitre and sulphur enter. I have known cases filled with brilliant or
Chinese fire remain good for a week in winter; but I do not suppose that
even then their performance was at all what it would have been if they
had been prepared for a few hours only.
Many attempts have been made to secure these metallic ingredients from
corrosion. Some have stirred the filings in a varnish made of resin and
spirit; others have shaken them about in powdered black-lead, and so
coated them with this substance. But a coating of any kind is tolerably
certain either to rob the spark, which each particle of metal should
produce, of its brilliancy, or to render the composition during
combustion very smoky, and so impair the intended effect.
By far the most successful preparation of steel and iron that I have
noticed is the following:—A weak solution of asphalt in naptha is made,
and the filings or borings are stirred about in this. When it is thought
that they are thoroughly covered with it, the solution is poured off,
and the filings spread out upon a paper to dry. This plan will protect
them from rust for a little time longer than they would otherwise remain
uncorroded. But still the best plan is to prepare the compositions as
short a time as possible before they are to be fired.
The size that I recommend for cases which are intended to contain
Chinese fire is that called the _two-ounce_ case. To make them, the same
former may be used as was employed in the manufacture of Roman-candle
cases already described.
The paper and imperial board may be cut of the following sizes. Open
your sheet of paper, _of the 70-lb. thickness_, to its full size, and
divide it into three pieces, as shown in the following woodcut, Fig.
41:—
[Illustration:
Fig 41.
]
Then open your sheet of imperial board to its full size, and divide it
thus into nine equal pieces, Fig. 42.
So that by these arrangements one sheet of imperial board and three
sheets of 70-lb. brown paper will furnish you with material for _nine_
cases, each of which will be about nine and a-half inches in length.
[Illustration:
Fig. 42.
]
[Illustration:
Fig. 43.
]
My plan for rolling the cases is that which I have described in
paragraph 25, but which may perhaps, be rendered slightly more
intelligible by the accompanying sketch. Having pasted one of my strips
of paper and one piece of board all over on one side, and having brushed
some paste over my metal former, I lay the former across the strip of
paper about one-third of its whole length from the end nearest to me. I
then double the one-third of the strip, pasted side downwards, over the
former, on to the remaining two-thirds, Fig. 43, taking care that the
edges of the one are even and parallel with the edges of the other. Then
having made a crease in the upper fold just in front of the former, I
put into this crease the pasted piece of imperial board, and roll up the
whole together. It is necessary, however, _to paste the upper side_ of
the fold of paper which you have made round the former. This I have
always found a very quick, and easy, and perfect method of preparing
cases of any kind. I trust that I have rendered my meaning plain, as I
shall have occasion to refer frequently to this operation. The rolling
board must, of course be used.
The cases when made are to be choked, _while wet_, precisely in the same
manner as described for rocket-cases, only it must be remembered that
their aperture may be almost choked up, because when it has been
reopened by the point over which they are loaded, _it must not be more
than one-third of the interior diameter of the case in size_.
Having described the manufacture of the cases. I now proceed to give the
formulas for the composition of