placed in a product prepared from linseed
oil. It was found that a material could be produced from it which
would to a certain extent equal India rubber compositions in
elasticity and toughness.

It was argued that linseed oil varnish, when correctly prepared,
should be clear, and dry in a few hours into a transparent, glossy
mass of great tenacity. By changing the mode of preparing linseed oil
varnish in so far as to boil the oil until it became a very thick
fluid and spun threads, when it was taken from the boiler, a mass was
obtained which in drying assumed a character resembling that of a
thick, congealed solution of glue.

Resin was added to the mass while hot, in a quantity depending upon
the product designed to be made, and requiring a greater or less
degree of elasticity.

Many other recipes have been advocated at different times to make a
product resembling caoutchouc out of linseed oil in combination with
other substances, but all have failed to give satisfaction, save as
adulterants to pure rubber.

Among the best compounds in use in rubber factories at present is one
made by boiling linseed oil to the consistency of thick glue.
Unbleached shellac and a small quantity of lampblack is then stirred
in. The mass is boiled and stirred until thoroughly mixed. It is then
placed in flat vessels exposed to the air to congeal.

While still warm the blocks formed in the flat vessels are passed
between rollers to mix it as closely as possible. This compound was
asserted by its inventor to be a perfect substitute for caoutchouc. It
was also stated that it could be vulcanized. This was found to be an
error, however. The compound, upon the addition of from 15 to 25 per
cent. of pure rubber, may be vulcanized and used as a substitute for
vulcanized rubber.

Compounds of coal tar, asphalt, etc., with caoutchouc have been
frequently tested, but they can only be used for very inferior goods.

The need for a substitute for gutta percha is even more acute than for
artificial India rubber. A compound used in its stead for many
purposes is known as French gutta percha. This possesses nearly all
the properties of gutta percha. It may be frequently used for the same
purposes and has the advantage of not cracking when exposed to the
air.

Its inventors claimed that it was a perfect substitute for India
rubber and gutta percha, fully as elastic and tough and not
susceptible to injury from great pressure or high temperature.