Fossil resin, from fossilized conifers millions of years old. Among the resins, it is the hardest and results practically insoluble in all solvents, with the exception of the oils, in which it is partially soluble under heat. Anciently, the term was utilized to indicate many hard resins, including sandarac, and it is probably with reference to this that they were commended for optimal properties: amber furnishes a varnish that is very dark and difficult to remove, thus not adapt in pictorial techniques.