APPARATUS.
In the practical part of Pyrotechny, the constructing and due
proportioning of the moulds is a very material consideration, for on
these the goodness of the article depends nearly as much as on the
purity of the ingredients. They consist chiefly of solid and hollow
cylinders made either of wood or metal; those that are hollow are
called _moulds_, and those that are solid _formers_; both are used
in the construction of rockets; similar cylinders either of wood
or metal are used for ramming down the composition; a machine for
contracting the aperture of the cases, the operation of which is
called _choaking_; another for boring them after they are filled; and
a simple apparatus for grinding the materials previous to the cases
being filled, as well as others of less importance, which we shall
choose rather to describe as their assistance is required.
We shall begin the important Apparatus with describing those which
come most immediately into use.
1. GRINDING MACHINES.--For the purpose of triturating or properly
mixing the several ingredients together, various contrivances have
been resorted to. A common iron mortar, such as is used by druggists
and apothecaries, is found to answer very well for grinding or
pounding the brimstone, charcoal, salt-petre, &c. _separately_; and
apothecary’s close sieves, fitted with wire-cloth, are the best
possible implements for obtaining the fire powder; but when corn
gunpowder is to be _mealed_, or the various ingredients are to be
mixed together, such mortars cannot be used, as the heat generated
by the continued action of the pestle might inflame the mixture,
and thereby place the life of the operator in imminent danger. To
obviate these dangerous probabilities a very simple contrivance has
been effected; this is called the mealing table, and for that purpose
has proved very speedy and effectual. It consists of a rectangular
elm board, with a rim round its edge, four or five inches high, at
one end of which a part of the rim is made to slide in a groove,
so that after mealing the powder it may be swept clean out from
the table. A representation of it may be seen at plate 1, fig. 3.
Fig. 4 is a small copper shovel, generally made use of for filling
and emptying the table. When about to meal a quantity of powder,
observe not to put too much on the table at once; but when you have
put on a moderate portion, take the muller (fig. 5,) and rub it
till all the grains are well broken; then sift it in a lawn sieve,
that has a receiver and top to it, such as is generally used by the
apothecaries, and that which does not pass through the sieve must be
returned to the table, and with an additional quantity ground over
again. Sulphur and charcoal may be ground in the same manner, only
these being much harder than powder the muller must be of ebony, or
any other hard wood, else the ingredients would stick in the grain
of the elm, and be very difficult to grind. As sulphur is apt to
stick and clod to the table, it will be found best to have one for
that purpose, as they are easily procured; this will be but little
trouble, and more than compensated by your sulphur being always kept
clean and well ground.
The following is another method for the above purpose, which some
consider equally effective. This is a mortar made of hard wood,
shaped like that of the druggists, with the bottom rounded within,
and having a wooden lid fitting close on the top, and in the centre
a hole just large enough to admit easily the stalk of the pestle, to
the lower end of which is connected a piece of marble terminating
in a spherical surface. With this apparatus gunpowder may be safely
ground to meal, or its ingredients mixed by the continued motion of
the pestle in the hole of the lid.
2. _Method of mixing the Ingredients._--Connected with that of
grinding is the operation of mixing the ingredients, and which is
considered a principal part of the business of Pyrotechny; and
indeed many articles depend as much on the well mixing as on the
proportion of their composition; therefore great care should be taken
in this part of the work, and particularly so in the composition of
sky-rockets. When you have about four or five pounds of ingredients
duly prepared for mixing, (which is a sufficient quantity to mix at
one time,) first put them together in some vessel convenient for the
purpose, then work them about with your hands, till their various
natures are pretty well incorporated; after which put them into your
lawn sieve with the receiver and top to it, and sift it into some
other clean vessel, and if any remains that will not pass through
the sieve, grind it again till fine enough; and if it be suffered
to pass twice through the sieve it will be more than the trouble
the better. For rockets and all fixed works, from which the fire is
to play regular, the ingredients must be prepared as above; and
we may observe here, that all compositions which contain steel or
iron filings must be mixed or shifted with the copper shovel, for
the hands are apt to impart a moisture, which is injurious to their
nature. Nor will any works which have iron or steel in their charge
keep long in damp weather without being properly prepared, as was
directed in the preceding Section.
There are several other moulds and apparatus made use of, but as
most of them are used in the making of rockets, and some few other
articles, and are so immediately connected with the practice thereof,
we think their use and application will be better understood when we
come to treat of that article in the next Section, rather than by
entering their descriptions in this place.