A. Levy contributes the following brief account of this subject to the
_Moniteur Scientifique_:
The crude gum cut in irregular strips is passed five or six times
between two strong rolls sixteen inches in diameter, and making two
or three revolutions per minute. These rolls are kept wet by water
trickling on them. This broad strip of gum is perforated with foreign
substances and looks like a sieve. It is next put in the cutting
machine, a horizontal drum provided with an axle having knives on it. So
much heat is produced by this cutting that the water would soon boil if
it were not renewed. A second machine of this kind completes the cutting
and subdividing, and expels the air and water from it. The mass is then
pressed in round or quadrangular blocks.
The vulcanization of thin articles from one twenty-fifth to
one-sixteenth inch thick, is done by Parkes' patented process, that is,
dipping it in carbon disulphide for a short time, to which chloride or
bromide of sulphur has been added, and when the solvent has evaporated
the sulphur remains behind. Balls, ornamental articles, and surgical
apparatus are dipped into melted sulphur at 275° or 300° Fahr.
The third most important process consists in mixing in the sulphur
mechanically with the gum in the cutting machine.
After the pieces have received the form they are to have they are heated
with steam or hot air to 275°. Flat articles are vulcanized between
press plates heated by steam. This vulcanization is said to have been
discovered accidentally by searching different colored stuffs, some of
which were dyed yellow with sulphur; the latter stood well.
Hard rubber contains more sulphur, and is heated longer and higher.
Small or fine tubes and hose are made by a continuous machine that
presses it through a hole with a core to it. Large hose is made by
wrapping strips around iron rods or tubes. The little air balloons
are made in Paris (their value is $300,000) by Brissonet from English
Mackintosh cloth. Powdered soapstone is strewed over it in cutting. The
edges are united by hammering on a horn anvil, or by machinery through
simple adhesion, and the cut surfaces are smooth.
* * * * *