Mastic Gum Varnish is a final painting varnish based on the natural mastic gum Mastic is used as a raw material in the production of some varnishes. Mastic varnish was used to protect and preserve photographic negatives also from ancient times was used for application on dry paint. It produces a high-gloss; high-build film with a golden glow Resistant film 33% Mastic gum (from Chios) Mastic resin is found in varnishes. here in a art store in Germany in the city of Bonn it is used for the fine arts.