Venice turpentine

A thick, viscous exudation from the Austrian larch tree, Larix decidua, containing 63% resinous acids, 20% terpenes, and 14% resins. It has been used since the 16th century in small amounts to produce an enamel-like surface that is non-yellowing. However, it is not used as a varnish because it quickly becomes dark and brittle when exposed to oxygen and light. It is also used as a mounting medium for light microscopy and as a plasticizer in glue paste linings.