Liquitex
Acrylic Matte Gel Medium

This medium has all the properties of Gloss Gel Medium except that it dries translucent to a satin matte finish. It has a viscosity and body similar to heavy acrylic color, and possesses greater adhesion than most other gel mediums. Acrylic Matte medium also extends acrylic paints and increases their brilliance without changing the thickness of the paint.