MATERIALS.
Having in the preceding Section, entered somewhat largely on
the nature and properties of Gunpowder, and consequently of the
ingredients which compose it, any further observations on them would
be unnecessary, providing the ingredients and proportions always
remained the same. But as the ingredients used in the manufacture of
that article are frequently employed in various other proportions,
to form compositions for filling fire-works, it is necessary to give
some further directions for the choice and purification of these
articles, which, together with the apparatus made use of in the
making of fire-works, will form the subject of the present section.
1. NITRE.--Among the various articles made use of in the composition,
none are of greater importance than salt-petre, for on the quantity
and purity of this depends all the force and much of the brilliancy
of the fire. The most common sort is that usually sold by the
grocers, and is generally in large lumps formed of an assemblage
of small crystals somewhat transparent, and often mixed with earthy
matter and many other impurities. In its purest state it is in the
form of small six-sided prismatic crystals, not apt to grow moist or
powdery on exposure to the air. The pure nitre is now become very
expensive, so it is of consequence to know how the common nitre,
or nitre of commerce may be purified, for it is found to answer no
purpose in Pyrotechny unless such change or purification in it have
been effected.
Nitre is found, (like most of other saline bodies) to be much more
soluble in boiling water, than in water of the ordinary temperature.
If therefore the nitre of commerce be dissolved in a small quantity
of boiling water, and the solution be properly strained, the liquor,
when cold, will afford crystals that are very pure. The following
is the most convenient method of proceeding: dissolve the nitre in
boiling water, (which should be soft water,) in the proportion of
about a quart to each pound of nitre; and that the solution may be
more easily effected, let the nitre be reduced to a powder, previous
to its being immersed, and let the vessel containing the nitre and
water be kept at the boiling heat till all the salt is dissolved;
then strain the liquor, while hot, through thick blotting paper,
placed in a clean funnel; and set by the filtered liquor in a shallow
vessel, in a cold place, to crystallize. The crystals thus obtained
are to be dried, first in blotting-paper, and then before the fire,
and kept for use. From the remaining solution, which is sometimes
called _mother-water_, fresh crystals may be procured by boiling it
in a clean tin vessel till a filming scum arises to the surface, then
filtering it through paper, and setting it aside to crystallize as
before.
Very pure nitre may also be obtained from damaged gunpowder, which
may be sometimes procured at a cheap rate, at the shops where it is
sold for this purpose. The damaged powder must be ground with a small
quantity of hot water, in a large wooden or stone mortar, otherwise
it may be boiled over a gentle fire, with as much water as will cover
it, till as much as possible of the nitre is dissolved; the liquor is
then to be strained through a thick flannel bag, afterwards filtered
through blotting-paper while hot, the sediment to be boiled down till
a film rises on the surface; again filtered and set by to cool and
crystallize, as directed in the process for the former method.
As the nitre must always be reduced to fine powder, previous to
mixing it with other substances, this is easily done by dissolving
it in a little more than its own weight of boiling water, keeping
the solution over a gentle fire, and continually stirring it with a
flat stick till all the water is evaporated, when the powder is to
be taken out and dried before a gentle fire; during which, care must
be taken not to let it remain too long, or exposed to too great a
heat, otherwise it will be melted into a firm cake. The drying may be
completed by suffering it to remain a sufficient time on paper before
the fire. For the purification of salt-petre, both these methods
may (by attending to the foregoing instructions,) be practised with
success; but of the two, we would more strongly recommend the former.
2. SULPHUR.--Sulphur is the next ingredient, in regard to importance,
as being the most inflammable material we are acquainted with. It
exists in three states, in all of which it is occasionally employed
in fire-works; the first is that brought from the neighbourhood of
volcanoes, and is called _native sulphur_, but more commonly _sulphur
vivum_, though (it may be observed,) what is sold in the shops under
this name is a drossy powder, the refuse left after purification.
The second is that in the roll, called _roll sulphur_, or _stone
brimstone_. The third is the _sublimed sulphur_, or as it is commonly
called _flower of sulphur_; this when genuine is the purest, and
is found to answer best for all nice and delicate articles, and
from its being already in a state of powder it is by far the most
convenient, as the others require to be ground or mealed previous
to their being used. The first kind is the cheapest, and answers
pretty well for all large and coarse articles, but as it is most
frequently mixed with earthy matter and other impurities, the use of
it we would not very much recommend. The second is found to be the
strongest, and which is mostly used, particularly for most of the
ordinary articles; but such is the desire of gain, that this article
of sulphur is not suffered to pass through the hands of dealers
without its quality being reduced by adulteration, which they effect
by mixing with it rosin, flour, &c.; when pure it is of a bright
yellow colour, dense but not too heavy, easily cracks with the heat
of the hand, and the broken parts look bright and crystallized.
There is another kind of _sulphur_ (though not generally known among
dealers) which does not burn like the others, and what is rather
singular, it emits no sulphurous smell, for being put upon the fire
it melts just like common wax; this sort is found in great abundance
in Iceland near Mount Hecla, and Carniola. This sulphur is commonly
of a reddish colour, like that found in the straits of Heildesheim,
where it is likewise of several colours, as pale yellow and green,
and generally adheres to the surface of stone and rocks, from which
it may be easily broken off and collected; that which is perfectly
yellow of each kind is the best. That of our first description,
or _sulphur vivum_, is sometimes called _quick sulphur_ from its
undergoing no change by fire, since its productions by nature; and
in some countries it is called _virgin sulphur_, because the women
and girls in Campania frequently make a kind of paint of it, for
no less delicate purpose than that of beautifying the face. Should
either kind be met with in an impure state the following method may
be applied for the purpose of purification.
3. _To purify Sulphur._--Melt a quantity of it in an iron pan, by
which means the earthy and metallic parts will be precipitated, and
then pour it into a copper-kettle, where it will form another deposit
of the impure matter with which it is mixed; after keeping it for
some time in a melted state, pour it into cylindric wooden moulds,
for the purpose of forming it into sticks; the moulds may be about an
inch in diameter; their length may be various. If the sulphur should
take fire during this operation it may be quickly extinguished by
covering the pan close over at the top.
4. CHARCOAL is also a considerable ingredient in our compositions,
but is of a much more simple nature than that of the foregoing ones.
It may generally be procured at the hardware shops, or at foundries,
or it may be easily prepared, for which put a quantity of small
pieces of wood, such as beech or alder, into a large earthen or iron
pot, filling up the vacuities, and covering the top with sand; then
placing the pot in the middle of a strong fire, and keeping it at a
red heat for two or three hours, as the sand excludes the air, the
wood is thus reduced to charcoal without the possibility of its being
consumed; and when the pot is cold, the charcoal is to be taken out
and kept for use in some very dry place. Small quantities should only
be made at a time, as it is always best newly prepared.
5. STEEL-DUST is another important ingredient in fire-works, for
being mixed with mealed powder or some other composition, and the
mixture inflamed in a proper tube, or case, the jet of fire produces
a most brilliant appearance by the sparks arising from the ignition
of the iron in the oxygen gas of the nitre.
Iron-filings, (for this Steel-dust is nothing more than pure iron
reduced into small particles by filing or some other method,) when
free from rust, and not mixed with any impurities, answer very well;
but fire-work makers generally prefer cast-iron reduced to powder,
by beating thin plates of it on a cast-iron anvil with a heavy
hammer, and sifting the broken particles through sieves of brass or
iron wire, of different degrees of fineness, so as to separate the
particles into grains of various sizes, according to the magnitude
of the pieces. The grains thus sorted have been called _iron-sand_,
and have been distinguished into sand of three or four _orders_,
according to their respective fineness; thus the sand that passes
through the finest sieve, is called sand of the _first order_; and
that which passes through the second, sand of the _second order_;
and so on to the fourth, which is generally very coarse. The finest
is calculated for fire-works of the smallest size, the second for
pieces somewhat larger, and that of the last order, only for pieces
of the largest size, such as gerbes of six or eight pounds, the
composition of which being of proportionate strength to bring such
large particles into a state of ignition.
As these grains are very apt to rust by keeping, they should be
preserved either in close stopped bottles, well dried, or in boxes
that shut close, and are lined with paper moistened in linseed oil.
It sometimes happens that fire-works may be required to be kept a
long time, or sent abroad; neither of which could be done with the
brilliant fires, if made with filings unprepared, for this reason,
that the salt-petre being of a damp nature it causes the iron to
rust; the consequence of which is, that when the works are fired
there will appear but very few brilliant sparks, but instead of them
a number of red and drossy sparks; and besides, the charge will be
so much weakened that if this were to take place in wheels, the fire
would scarcely be strong enough to force them round; but to prevent
such failures in the firing of them, the filings, or iron-sand, may
be thus prepared:--
6. _To prepare iron-sand._--Melt in a glazed earthen pan some
brimstone over a slow fire, and when melted throw in some filings,
which keep stirring till they are all covered with brimstone, this
must be done while it is on the fire; then take it off and stir it
very quickly till cold, when it must be rolled on a board with a
wooden roller, till broken as fine as corned powder, after which sift
from it as much of the brimstone as possible.
_Second method._--There is another method of preserving filings so as
to keep two or three months in winter, which is done by rubbing them
between strong brown paper, which has been previously moistened with
linseed oil. In heating the brimstone the caution given in Article 3,
must be observed in the event of its catching fire.
We must observe in fine on this article, that it will be well to
anticipate a little trouble in the preparation of this granulated
Iron-sand, for cast-iron being of so hard a nature as not to be cut
by a file, we are obliged to pulverize it, or reduce it to grains by
the method we have described, which is rather difficult to perform;
but when we consider what beautiful sparks this iron yields, no pains
should be spared to granulate such an essential material.
We must further observe, that when these plates of iron cannot be
procured, an old cast-iron pot may be employed; but especial care
must be taken that its surface be perfectly free from rust and other
impurities previous to its being pulverized, otherwise it will
entirely destroy the effect it is intended to produce.
It is to the Chinese we are indebted for this method of rendering
fire so brilliant and variegated in its colours, who discovered
it long before Father d’Incarville made it known to the European
countries. This sand, when it inflames, emits a light exceedingly
vivid; and it is surprising to see fragments of this matter not
larger than a poppy seed, form all of a sudden luminous flowers of
stars, twelve and fifteen lines in diameter. These flowers are also
of different forms, according to that of the inflamed grain, and
even of different colours, according to the matters with which the
grains are mixed. But rockets, into which this composition enters,
cannot be long preserved, unless prepared as described in the early
part of this article.
There are many other substances occasionally employed in the
composition of fire-works, but as they can be procured at all
Chemists and Druggists ready for the purpose, we consider it
unnecessary to give any detail respecting them, further than
enumeration. They are chiefly the following, viz. _Camphor_, which is
used to improve the appearance of the fire; _Antimony_, or _Sulphuret
of Antimony_, _Sal-ammoniac_, _Verdigrease_, and _Pitch_, for giving
to the fire different and particular shades of colour; _Flowers
of Benjamin_, or _Benzoic-acid_, for imparting to it an agreeable
odour; and _Spirits of Wine_, or _Camphorated Spirits_, for mixing
up the ingredients into a paste. These liquids are found to answer
much better than common water, or gum-water, which is sometimes
used, as they do not dissolve the salt-petre, and are therefore
not so liable to produce a separation of the materials employed.
_Lamp-black_ is sometimes used instead of charcoal, and is supposed
to have the effect of diminishing the heat of the fire, while it does
not materially lessen its brilliancy. Thence it is a considerable
ingredient in what is called _cold-fire_, the seeming paradox of
which we shall hereafter reconcile. For the same purpose, that of
diminishing the force of the composition, _powdered glass_ and
_saw-dust_ have been frequently employed; but probably these effects
might be better, and with more certainty answered, by lessening the
proportion of nitre.
7 OIL OF CAMPHOR.--This liquid is frequently used for the purpose of
moistening the compositions; it is thus easily procured: put a small
quantity of Camphor into a brass mortar, and to it add some oil of
sweet almonds, sufficient to reduce it to a stiff paste, then work
the mixture well together, and it will turn to a green colour, after
which add a sufficient quantity of oil to liquify it for use. We must
observe on the use of this liquid, that the composition into which it
enters must be kept as much as possible from the air, as an exposure
to it will cause it to evaporate, and thereby cause a failure in the
exhibition.
8. BENZOIN.--Benzoin, or as it is vulgarly called Benjamin, is a
resinous matter obtained from the tree called _Benzoin_, and is
brought from different parts of the Indies, where it is found of
various kinds, and of different colours; the best is that which is
full of white spots and is easily broken. It is used in odoriferous
fire-works, but prior to which it must be reduced to a fine powder,
which may be effected by the following method:--put about three or
four ounces of Benzoin grossly pounded into a deep and narrow earthen
pot, and cover the pot over with a cone of thick paper, which tie
closely round the edge, then place the pot over the fire and apply a
moderate heat; after the interval of an hour take off the cone, and
you will find some flower sticking to the under-side of it; or in
the language of chemistry, the acid is sublimed and is deposited on
the paper; the cone must be returned to the pot, and the operation
continued till the flower appears very white and fine.
The acid which is frequently used may be obtained by digesting
Benzoin in sulphuric acid, and by this it is obtained much purer and
in finer crystals than by any other method.
On this article we deem it requisite to give the above information;
but to the private practitioner, it will be more eligible to purchase
it ready prepared.