Gunpowder is, to produce that which shall give equal results with equal
charges; the greatest regularity should therefore be observed in this
stage. The millman should have great experience; the runners and beds
should be, as nearly as possible, the same size and weight, and driven
at the same speed throughout the factory; at any rate, each charge
should be worked to the same number of revolutions; the motion of the
runners should also be as uniform as possible, which is very
satisfactorily accomplished by each water-wheel being regulated by a
governor.
BREAKING DOWN THE MILL CAKE.
~Breaking down the mill cake.~
~Object of mealing.~
The mill cake, after it comes off the bed of the incorporating mill, is
placed in wooden tubs, and taken to small-expense magazines, and from
there, in about twelve hours, to the breaking-down house; the object of
the machine from which this takes its name, is to reduce the cake to a
convenient size for the hydraulic-press box, and also that, by being
crushed again to meal, it may get a more even pressure. It consists of a
strong gun-metal framework, in which are fixed two pairs of fine-toothed
or plain rollers, which revolve towards each other, working in spring
collars, so that on any hard substance getting in by mistake, they would
open, and allow it to pass through, thereby preventing the dangerous
friction which would otherwise result. A hopper, or upright wooden
funnel, capable of holding about 500 lbs. is fixed at one end of the
machine, and an endless canvass band 2ft. 6in. wide, having strips of
leather sewn across at intervals of four inches, passes over one roller
at the bottom of the hopper, and one at the top of the machine. When set
in motion, this conveys the cake from the hopper to the highest point of
the band; it then falls through the first pair of rollers, and from
thence through the second, passing in the form of meal into small wooden
carriages underneath, which, as they are filled, move forward by a
self-acting motion, making room for others. The mill cake thus broken
down, is fit for the press.
PRESSING THE MEAL BY THE HYDRAULIC PRESS.
~Hydraulic Pressure.~
The meal is now subjected to very powerful pressure; and, in order to
explain the way in which this is effected, a short description of the
apparatus must be given. The principle of the hydraulic press is so
familiar to most, that it will be unnecessary to do more than show how
the power is applied (vide plate 2).
~Description of box.~
A very strong oak box, 2 feet 6 inches square, and 2 feet 9 inches deep,
is constructed so that two of the sides of the lid will fall back on
hinges, or form a compact solid box when screwed firmly together.
Forty-six copper plates, 2 feet 5¹⁄₂ inches square, slide vertically
into this box, and are kept five-eighths of an inch apart by two metal
slips with corresponding grooves, which can be removed when necessary.
~Quantity pressed.~
~Amount of pressure.~
About 800 lbs. of the meal is put into this box while the plates are in
the position we have described. When full, the slips are withdrawn, the
plates being then only separated by the powder between them: the lid is
now firmly screwed down, and the box turned over by an arrangement of
pulleys, so that the plates which were vertical will now be horizontal.
The present upper side is then unscrewed, and a travelling crane, moving
on a rail overhead, is lowered till the claws attached to it hook on to
two trunnions fixed on the sides of the box; it is now hoisted by means
of a handwheel windlass, and the box being suspended, is pushed easily
by means of the rail, and deposited in this position on to the table of
the ram under the press block. The pumps are now set in motion by a
water-wheel, and are allowed to work up to the required pressure, which
is about seventy tons to the square foot; it is then conveyed from under
the block in the same manner, and very easily unloaded. The press cake
is then taken out in layers between each plate, resembling dark pieces
of slate, about half an inch in thickness. After a day or so, this
hardens so much as to be difficult to break, and the appearance of the
fracture resembles that of the finest earthenware. Many important
advantages are gained by this pressure, of which the following are the
principal:--
~Reasons for pressure.~
First, the density of the powder is increased, which prevents it falling
to dust in transport, or by rough usage. Secondly, its keeping qualities
are improved, for it withstands the action of the atmosphere, and
absorbs less moisture than a porous light powder. Thirdly, it produces
more grain in the manufacture than mill cake; and a less proportion,
consequently, is lost in dust. Fourthly, a closer connection of the
ingredients is obtained. Fifthly, a greater volume of inflammable gas is
produced from a certain bulk, than from a corresponding bulk of lighter
powder.
~Disadvantages of pressure.~
The range, however, is lessened, from a greater quantity being blown out
of a gun unignited; but this small loss is more than counterbalanced by
the former advantages, and actually it is only perceptible in newly-made
powder; for a light, porous powder soon loses its superior range from
its absorption of moisture, while that of the dense powder remains
unaltered.
GRANULATING THE PRESS CAKE.
~Mode of granulation.~
~Screening.~
The next process is granulation, or reducing this press cake into the
proper sized grain for cannon, musket, or rifle powder. The machine
which effects this is very beautifully contrived, and is entirely
self-acting, obviating the necessity of any one being in the building
while it is in motion. It resembles, in appearance and action, the
breaking-down machine, except that it is larger, and is fitted with
three pairs of toothed rollers, of different degrees of fineness,
working in the same kind of collars already mentioned, so that, on any
hard substance passing through, they would open accordingly, and thus
prevent friction. At one end of the machine is a wooden hopper, or
funnel, which is filled with the press cake. This is contrived so as to
rise gradually by the motion of the machine, and constantly to supply an
endless band, similar to the one described in the breaking-down house.
When the cake arrives at the highest point of this band, it falls over,
and is granulated between the first pair of gun-metal rollers. Under
each pair is a screen, covered with 8-mesh wire. All that is not
sufficiently small to pass through, is carried on to the next pair of
rollers; and, in like manner, that which does not pass through the
second screen is carried to the third pair. In addition to these
screens, there are three oblong sieves covered with 8- and 16-mesh wire,
and 56 cloth respectively, fixed under, and parallel to, each other,
each being separated by about four inches of space, running at an
incline just below the three pairs of rollers; these all lead to little
wooden carriages placed on the opposite side of the machine, which are
divided so as to collect the different sized grain as it passes down. To
facilitate the separation and sifting of the powder, and to prevent
masses of it forming and clogging up the wire, a shaking motion is
imparted by a circular wheel attached to the framework of these sieves
revolving against an octagonal one fixed to the machine. The grains
which pass through each screen below the rollers fall on the upper one
of these three last-mentioned sieves. That portion which passes through
this, and is retained on the 16-mesh wire, is cannon powder; that
passing through the 16-mesh sieve, and retained on the 56-cloth, is fine
grain; and a board, running also parallel underneath, retains the dust
that passes through the cloth.
~Chucks regranulated.~
The “chucks,” as they are called, or those grains that are too large to
pass through these different sieves, are collected in the same way as
the grain, and undergo the process of granulation again.
DUSTING LARGE-GRAIN POWDER.
~Object of dusting.~
~How performed for large-grain.~
~Glazed at same time.~
The keeping qualities of powder are very much improved by removing the
dust, which quickly absorbs moisture from the atmosphere. This
operation, for large-grain, is performed by cylindrical reels, about
8ft. 6in. long, and 3ft. 8in. in diameter, clothed with 28-mesh canvas,
which revolve at the rate of thirty-eight times per minute. Those for
large-grain are called horizontal reels, in contradistinction to those
for fine-grain, that are called slope reels. Each is enclosed by a
wooden case, to prevent the dust flying about the house. When the powder
has run its time, one end of the reel is lowered. It then runs out into
barrels placed to receive it. This entirely separates the dust, and
imparts a fine black gloss, which is sufficient glazing for the
large-grained powder.
DUSTING FINE-GRAIN POWDER.
~Dusting fine-grain.~
The fine-grain powder has a much greater proportion of dust when it
leaves the granulating house than the large-grain, and it is found
necessary, on this account, to use a different kind of reel. They
resemble those for the former powder, except that they are covered with
44-mesh canvas instead of 28, and are placed at an incline which
prevents their being choked up with the quantity of dust; each end is
also open, and a continuous stream of powder, fed by a hopper, passes
through while they revolve, and pours out at the lower end into barrels.
This process is repeated a second time, which sufficiently frees it from
dust.
GLAZING FINE-GRAIN POWDER.
~Glazing fine-grain.~
The fine-grain powder thus dusted, is then glazed for three hours in
barrels capable of holding 300lbs. which are 3ft. 6-in. in length, and
2ft. 8-in. in diameter, revolving at the rate of thirty two times in a
minute. By the mere friction of the grains against each other and the
inside of the barrel, a glaze is imparted, presenting a fine polished
surface to the grain.
~Object of glazing.~
Powder glazed in this way withstands the action of moisture to a far
greater extent than unglazed powder, and in transport very little dust
is formed.
STOVING OR DRYING POWDER.
~Drying.~
A drying-room, heated by steam pipes, is fitted with open framework
shelves, on which rests small wooden trays about 3ft. long, 1ft. 6-in.
in breadth, and 2¹⁄₂in. deep, having canvas bottoms; on each is spread
8lbs. of powder. This room holds about 40 barrels, or 4,000lbs., which
remains in it for twenty four hours, and is subjected to a heat of 130°
Fahrenheit for sixteen hours, communicated by steam passing through
pipes arranged horizontally on the floor of the room. The temperature is
raised and lowered gradually, otherwise the too sudden change would be
likely to destroy the texture of the grain. The ceiling and roof are
fitted with ventilators, through which all the moisture escapes, so that
there is a constant current of hot air circulating through the room. It
is of the greatest importance that the vapour should be carried off;
for, if this is not effectually done, on the decrease of temperature, it
would return to its liquid state, and form again on the powder.
FINISHING DUSTING.
~Final dusting.~
~Barrelling.~
The action of heat however produces a small portion of dust; both these
powders, therefore, when they leave the stove, are reeled in horizontal
reels, clothed with 28 and 44-mesh canvas respectively, for one hour and
a half. This perfectly separates any remaining dust, and gives the
finishing glaze to the large-grain powder. This is the final process,
and the powder thus finished is taken to the barrelling-up house;
weighed out into barrels holding 100lbs. each; marked L. G.
(large-grain), and F. G. (fine-grain), as the case may be; and stored in
magazines.
EXAMINATION AND PROOF OF GUNPOWDER.
~Desired properties of gunpowder.~
~Specific gravity.~
~Strength.~
~Purity.~
The great and ultimate object to be attained in the manufacture of
Gunpowder is, not so much to produce that which ranges the highest, as
one that shall be durable in its texture, not easily deteriorated by
atmospheric influence or transport, and one with which equal charges
shall produce equal effects. It should present uniformity in the
appearance of its grains, which should be angular, crisp and sharp to
the touch, not easily reduced to dust by pressure between the fingers,
or dusty in handling; its specific gravity should not be under 55lbs. to
the cubic foot, (that of Waltham Abbey is generally 58lbs.) taking water
at 1000ozs.; its strength is tested by firing three rounds from an 8
inch mortar, throwing a 68-pounder solid shot with a charge of 2oz. this
should give a range of from 270 to 300 feet. The distance however,
varies considerably, according to the state of the atmosphere, and the
density of the powder: for, the greater the density, the less the range
in small charges. Half an ounce flashed on a glass plate should leave
little or no residuum; should white beads or globules appear, it is a
sign of imperfect incorporation.
PROOF OF MERCHANT’S POWDER.
The following are the different proofs merchant’s powder is subjected
to:--
Lots of 100 barrels are sent in, marked with the number of the lot and
the maker’s name on the head of each barrel. 25 per cent. of these are
unheaded in the examining house; the Proof Officer then--
~If dusty.~
First, takes a bowl out of each barrel, and holding it about three feet
above, pours it out quickly; should there be a good deal of dust, it is
satisfactorily shown by this means.
~Firmness.~
~Size of grain.~
Secondly, it is handled and pressed between the fingers, to test the
firmness of its grain; and should there appear to be any great
difference in the proportions of different sizes to that laid down as a
standard, it is sifted and compared accordingly, being rejected should
the quantities fall short or exceed the sample in any great degree.
~Density.~
Thirdly, a barrel or two are selected, and the powder poured into a
hopper, under which is placed a box very carefully constructed, so as to
hold exactly a cubic foot. A slide is now withdrawn at the bottom of the
hopper, and the powder allowed to run into the box in a continuous even
stream until it is piled up; the hopper is then removed, and the powder
struck off with a straight edge, level with the top of the box. The
weight is now carefully taken, that of the latter being subtracted;
should this not amount to 55lbs. it is rejected, as not being of
sufficient density.
~Strength by range.~
Fourthly, samples are taken from every barrel, and lot for the firing
proof.
Firing Proof.--An average of nine rounds of sample Waltham Abbey powder
is taken, three rounds being respectively fired at the beginning,
middle, and end of the proof, from the same kind of mortar before
mentioned, with a charge of 2oz. An average of three rounds of each lot
of the merchant’s powder is also taken; should it fall short by more
than 1 in 20, it is rejected.
~Purity by flashing.~
Fifthly, to ascertain if any residuum or ash is left after ignition,
about half an ounce is burned on a clean glass plate, and fired with a
hot iron. The explosion should be sharp, and produce a sudden concussion
in the air; and the force and power of this concussion should be judged
by that of known good quality. Few sparks should fly off, nor should
white beads or globules appear, as it would be a sure indication, as we
have before explained, of insufficient incorporation. It is also
subjected to a second proof.
~Purity by weight after exposure to damp.~
Second proof.--A sample of 1lb. from each lot, carefully weighed up, and
a similar sample of the comparison powder, is exposed for three weeks in
a box perforated with holes (called a damp chest), to the action of the
atmosphere. This box is placed under cover, so that it is sheltered from
the wet, but that the moisture can get to it. If, at the end of this
time, there is a greater proportion of difference in range between them
than one-twentieth, it is rejected. The pounds are also very carefully
weighed up again, to ascertain the comparative absorption of moisture.
This is called the hygrometric test.
REMARKS ON THE PROOF OF POWDER BY THE EPROUVETTES.
~By eprouvettes or pendulum.~
By comparing the results of the proofs by the eprouvettes with those
furnished by the cannon pendulum (vide plate 1, fig. 2 and 3), it will
appear that the eprouvettes are entirely useless as instruments for
testing the relative projectile force of different kinds of powder, when
employed in large charges in a cannon. Powders of little density, or of
fine grain, which burn most rapidly, give the highest proof with the
eprouvettes, whilst the reverse is nearly true with the cannon.
~Real use of eprouvettes.~
The only real use of these eprouvettes is to check and verify the
uniformity of a current manufacture of powder, where a certain course of
operations is intended to be regularly pursued, and where the strength,
tested by means of any instrument, should therefore be uniform.
~Best proof, by service charges.~
The only reliable mode of proving the strength of Gunpowder is, to test
it with service charges in the arms for which it is designed; for which
purpose the balistic pendulums (vide plate 3), are perfectly adapted.
~Best proof for small arms.~
For the proof of powder for small arms, the small balistic pendulum is a
simple, convenient, and accurate instrument.
~Common eprouvette.~
The common eprouvettes are of no value as instruments for determining
the relative force of different kinds of Gunpowder.
OF THE SIZE OF GRAIN FOR GUNPOWDER.
~On size of grain.~
With regard to the particular size of grain for Gunpowder, I am
confident great improvements might be made, both in obtaining greater
regularity of effect and propelling force, by the adoption of a more
uniform even grain. There are at present half-a-dozen different sizes in
our cannon and musket powder; and I think it stands to reason, that the
more equal the size, the more uniform will be the ignition of all the
grains, and consequently the effect of the same charges will be much
more regular.
OBSERVATIONS ON THE MANUFACTURE OF GUNPOWDER ON THE CONTINENT AND
AMERICA.
It may not be uninteresting to have a slight knowledge of the method
employed on the Continent, &c., for the production of Gunpowder.
~Proportion of the ingredients.~
The proportions of the three ingredients vary slightly all over the
Continent and America, being as follows:--
SALTPETRE. CHARCOAL. SULPHUR.
France } 75 12.5 12.5
Belgium }
Russia 73.78 13.59 12.63
Prussia 75 13.5 11.5
Austria 75.5 13.2 11.3
Spain 76.47 10.78 12.75
United States 76 14 10
PRODUCTION AND PURIFICATION OF THE INGREDIENTS.
~Production and purification of the ingredients.~
The nitre is purified in a similar way to the new method employed at
Waltham Abbey, though it is seldom obtained with so faint a trace of
chlorides, owing probably to its being of an inferior quality, and of
higher refraction when it is imported.
The sulphur is supplied to the manufactories in France in the form of
roll sulphur, from Marseilles and Bordeaux, where there are very large
refineries.
The charcoal is prepared from dogwood, alder, willow, hazel, and poplar,
sometimes in pits, and occasionally in cylinders, as at Waltham Abbey.
At Wetteren, and in some parts of France, it is distilled by the action
of steam. The “charbon roux” taking its name from its brownish-red
tinge, from being only partially burned, was used formerly more than
now, as the powder made from it was found to injure and exert very
pernicious effects upon fire-arms.
PULVERIZING AND MIXING THE INGREDIENTS.
~Pulverizing and mixing the ingredients.~
The ingredients are generally pulverized in copper drums, capable of
holding 224 kilogrammes. Part of the charcoal is mixed with the sulphur,
and part of the sulphur with the saltpetre. They are then put into
separate drums, which revolve about twenty-five times per minute for
three hours, and in which are about 500 gun-metal or bronze balls, the
size of good large marbles. The ingredients are brought to the most
minute state of division by these means, and are then mixed all
together, for one hour, in similar drums covered with leather,
containing wooden balls.
INCORPORATING PROCESS.
~Incorporation.~
The fine powder thus obtained is sometimes merely moistened, so as to
form a stiff paste, and passed through rollers, the cake formed, being
dried and granulated. The incorporating cylinders are used occasionally,
but the more usual plan adopted on the Continent to effect this
operation is the stamping-mill, which requires a short description. It
is nothing more nor less than the pestle-and-mortar principle, each mill
consisting of from six to twelve bronze or wooden mortars bedded in the
floor of the building; they are the shape of the frustum of a cone, the
mouth being much narrower than the base; the pestles, or stampers as
they are called, are made of wood, shod with either very hard wood or
bronze, on which project wooden teeth about twelve inches long; a
vertical movement is imparted to them by a shaft worked by the
water-wheel having similar teeth attached; in its revolution it raises
the stamper about eighteen inches, which falls again as the projection
is disengaged, twenty five times in a minute. This operation is carried
on for twelve hours, during which period the charge (about 15lbs.) is
moistened at intervals, and routed up with a copper-shod spud; at the
end of this time the cake is taken out, and left to dry and harden; it
seldom receives any pressure--although, in some manufactories, presses
are being erected.
GRANULATING.
~Granulation.~
The cake is then granulated in sets of sieves fitting one into the
other, having perforated zinc bottoms of different degrees of fineness,
which are suspended from the ceiling of the room by ropes, an ash spring
being attached to each box holding the sieves, the cake is put into the
uppermost one with some gun-metal balls, and shaken backwards and
forwards, which motion the spring facilitates; it is thus broken up into
different sized grains, which are separated by passing through the
several meshes.
The grain formed is then dusted in bags or shaking-frames covered with
canvas, and then glazed in barrels.
STOVING OR DRYING.
~Drying.~
~Comparative merits of foreign and English gunpowder.~
In summer the process of drying is often performed in the sun, and in
winter by the steam stove, in the following way. The powder is spread
about three or four inches thick on a large canvas tray, under which is
an arrangement of pipes, which convey the hot air forced by a fan
through a cylinder heated by steam: it is considered to be sufficiently
dried in from three to four hours, during which time it is occasionally
raked about. In some manufactories it undergoes a further operation of
being dusted, and is then barrelled up for use. Generally the great
failure in the foreign manufacture is the neglect of the principal stage
of the fabrication, viz. incorporation; with the old stamping-mill, it
is quite impossible that the process can be carried out to the necessary
extent. The Continental powder is usually very soft in its grain,
dusty, and quickly absorbs moisture from the atmosphere; its density is
below the English powder, on account of its never being subjected to
pressure; consequently it is not so durable, and forms a good deal of
dust in transport; a great amount of residue is generally left in the
gun, and its strength, as a propelling agent, is far inferior to our
powders. On being flashed on a glass plate, instead of producing a
sudden concussion, like the sharp rap of a hammer, it burns more like
composition, throwing off a quantity of sparks.
NEW RIFLE POWDER.
The following mode of manufacturing rifle powder, appeared in Garrison
Orders at Woolwich, 31st December, 1859:
Composition in 100 parts:--
Saltpetre 75
Charcoal 15
Sulphur 10
---
100
The charcoal to be prepared from dogwood, burned slowly in cylinders
three hours. The composition to be worked under the runners for five and
a half hours, and submitted to a pressure of about 50 tons to the square
foot. The size of the grain to be that collected between sieves of 16
and 24 meshes. The grain to be glazed for five hours.
* * * * *
NOTE.--The foregoing, on the manufacture of gunpowder, is principally
taken from an article in the Aide Memoire (1860), by Major Baddeley,
Royal Artillery; Captain Instructor, Waltham Abbey.
ON MAGAZINES.