Black powder was used in all firearms until smokeless and other type
propellants were invented in the latter 1800's. "Black" powder (which
was sometimes brown) is a mixture of about 75 parts saltpeter
(potassium nitrate), 15 parts charcoal, and 10 parts sulphur by
weight. It will explode because the mixture contains the necessary
amount of oxygen for its own combustion. When it burns, it liberates
smoky gases (mainly nitrogen and carbon dioxide) that occupy some 300
times as much space as the powder itself.
Early European powder "recipes" called for equal parts of the three
ingredients, but gradually the amount of saltpeter was increased until
Tartaglia reported the proportions to be 4-1-1. By the late 1700's
"common war powder" was made 6-1-1, and not until the next century was
the formula refined to the 75-15-10 composition in majority use when
the newer propellants arrived on the scene.
As the name suggests, this explosive was originally in the form of
powder or dust. The primitive formula burned slowly and gave low
pressures--fortunate characteristics in view of the barrel-stave
construction of the early cannon. About 1450, however, powder makers
began to "corn" the powder. That is, they formed it into larger
grains, with a resulting increase in the velocity of the shot. It was
"corned" in fine grains for small arms and coarse for cannon.
Making corned powder was fairly simple. The three ingredients were
pulverized and mixed, then compressed into cakes which were cut into
"corns" or grains. Rolling the grains in a barrel polished off the
corners; removing the dust essentially completed the manufacture. It
has always been difficult, however, to make powder twice alike and
keep it in condition, two factors which helped greatly to make gunnery
an "art" in the old days. Powder residue in the gun was especially
troublesome, and a disk-like tool (fig. 44) was designed to scrape the
bore. Artillerymen at Castillo de San Marcos complained that the
"heavy" powder from Mexico was especially bad, for after a gun was
fired a few times, the bore was so fouled that cannonballs would no
longer fit. The gunners called loudly for better grade powder from
Spain itself.
How much powder to use in a gun has been a moot question through the
centuries. According to the Spaniard Collado in 1592, the proper
yardstick was the amount of metal in the gun. A legitimate culverin,
for instance, was "rich" enough in metal to take as much powder as the
ball weighed. Thus, a 30-pounder culverin would get 30 pounds of
powder. Since a 60-pounder battering cannon, however, had in
proportion a third less metal than the culverin, the charge must also
be reduced by a third--to 40 pounds!
[Illustration: Figure 16--GUNPOWDER. Black powder (above) is a
mechanical mixture; modern propellants are chemical compounds.]
Other factors had to be taken into account, such as whether the powder
was coarse-or fine-grained; and a short gun got less powder than a
long one. The bore length of a legitimate culverin, said Collado, was
30 calibers (30 times the bore diameter), so its powder charge was the
same as the weight of the ball. If the gunner came across a culverin
only 24 calibers long, he must load this piece with only 24/30 of the
ball's weight. Collado's _pasavolante_ had a tremendous length of some
40 calibers and fired a 6- or 7-pound lead ball. Because it had plenty
of metal "to resist, and the length to burn" the powder, it was
charged with the full weight of the ball in fine powder, or
three-fourths as much with cannon powder. The lightest charge seems to
have been for the pedrero, which fired a stone ball. Its charge was a
third of the stone's weight.
In later years, powder charges lessened for all guns. English velocity
tables of the 1750's show that a 9-pounder charged with 2-1/4 pounds
of powder might produce its ball at a rate of 1,052 feet per second.
By almost tripling the charge, the velocity would increase about half.
But the increase did not mean the shot hit the target 50 percent
harder, for the higher the velocity, the greater was the air
resistance; or as Müller phrased it: "a great quantity of Powder does
not always produce a greater effect." Thus, from two-thirds the ball's
weight, standard charges dropped to one-third or even a quarter; and
by the 1800's they became even smaller. The United States manual of
1861 specified 6 to 8 pounds for a 24-pounder siege gun, depending on
the range; a Columbiad firing 172-pound shot used only 20 pounds of
powder. At Fort Sumter, Gillmore's rifles firing 80-pound shells used
10 pounds of powder. The rotating band on the rifle shell, of course,
stopped the gases that had slipped by the loose-fitting cannonball.
Black powder was, and is, both dangerous and unstable. Not only is it
sensitive to flame or spark, but it absorbs moisture from the air. In
other words, it was no easy matter to "keep your powder dry." During
the middle 1700's, Spaniards on a Florida river outpost kept powder in
glass bottles; earlier soldiers, fleeing into the humid forest before
Sir Francis Drake, carried powder in _peruleras_--stoppered,
narrow-necked pitchers.
As for magazines, a dry magazine was just about as important as a
shell-proof one. Charcoal and chloride of lime, hung in containers
near the ceiling, were early used as dehydrators, and in the
eighteenth century standard English practice was to build the floor 2
feet off the ground and lay stone chips or "dry sea coals" under the
flooring. Side walls had air holes for ventilation, but screened to
prevent the enemy from letting in some small animal with fire tied to
his tail. Powder casks were laid on their sides and periodically
rolled to a different position; "otherwise," explains a contemporary
expert, "the salt petre, being the heaviest ingredient, will descend
into the lower part of the barrel, and the powder above will lose much
of its goodness."
[Illustration: Figure 17--SPANISH POWDER BUCKET (c. 1750).]
In the dawn of artillery, loose powder was brought to the gun in a
covered bucket, usually made of leather. The loader scooped up the
proper amount with a ladle (fig. 44), and inserted it into the gun. He
could, by using his experienced judgment, put in just enough powder to
give him the range he wanted, much as our modern artillerymen
sometimes use only a portion of their charge. After Gustavus Adolphus
in the 1630's, however, powder bags came into wide use, although
English gunners long preferred to ladle their powder. The powder
bucket or "passing box" of course remained on the scene. It was
usually large enough to hold a pair of cartridge bags.
The root of the word cartridge seems to be "carta," meaning paper. But
paper was only one of many materials such as canvas, linen, parchment,
flannel, the "woolen stuff" of the 1860's, and even wood. Until the
advent of the silk cartridge, nothing was entirely satisfactory. The
materials did not burn completely, and after several rounds it was
mandatory to withdraw the unburnt bag ends with a wormer (fig. 44),
else they accumulated to the point where they blocked the vent or
"touch hole" by which the piece was fired. Parchment bags shriveled up
and stuck in the vent, purpling many a good gunner's face.