Even the presence of it is very poisonous to some people and all workers in it are more or less affected.
The solvent or vehicle of the modern copal varnishes consists principally of linseed oil with some turpentine.

Their base is Copal, a fossil, resinous substance of vegetable origin.

The gums of which they are made have been chemically altered by long exposure in the earth.

Other gums, as mastic, dammar, sandarac, and even resin are sometimes mixed with copal to cheapen the product or to cause more rapid drying.

Copal is a generic name given originally to all fossil resins.