Use polymer mediums for extending any viscosity of acrylic paint. Polymer mediums are translucent when wet, and they dry to a clear, flexible film which has excellent resistance to water and ultraviolet radiation. - Tri-Art Acrylic Polymer - Gloss, 500 mlTri-art Finest Acrylic Medium, GLOSS POLYMER 500ML - Their low viscosities make them ideal as glazing mediums and top coats. They are extremely adhesive and can be used in collage and craft applications such as découpage. Add them to resoluble water based paints such as watercolours and gouache to increase water resistance and flexibility.