Atelier - Acrylic Varnishes - 250ml - Gloss Medium & Varnish - Atelier Interactive Gloss Medium Varnish is water based, non-toxic, self-leveling and can be used either as a medium to change the sheen levels of acrylic paints or as an over-varnish for acrylic painting. Atelier Gloss Medium provides a non-tacky protective coating. Atelier Gloss Medium Varnish is creamy, mid-viscosity. Product made from hard acrylic emulsion. Gloss Medium is non-removable, however it can be overpainted.