It occurs in lumps from the size of small pebbles to pieces weighing four or five pounds.

The supply is said to be practically inexhaustible.
As to the manufacture of the Copal varnishes: first of all, a high grade oil is boiled at a high temperature, with different materials to oxidize it; for instance, red lead or oxide of manganese.

The heat throws off the oxygen from the red lead or manganese.

The oxygen is absorbed by the linseed oil, which is then put away to settle and age.
When a batch of varnish is made, the gums are melted in a large kettle and then the requisite amount of oil is added and these carefully boiled together.

This is removed from the fire and cooled down to a point, where turpentine can be added without volatilizing.