Gum Mastic is a tree resin, which dissolves into a clear varnish with alcohol or turpentine, but not with mineral spirits. Mastic varnishes are more prone to blooming and darkening with age than damar-based varnishes, and painting mediums that contain gum mastic can deteriorate in unpredictable ways. For this reason, it is primarily used in restoration, rather than in the production of artwork.
