Pebeo Vitrea 160 Vitrea 160 Frosted Medium is used to give a frosted or etched glass effect to the Vitrea 160 colours without affecting the technical characteristics or durability of the colours. Vitrea 160 can be applied to other thermostable surfaces which can withstand a temperature of 160C (325F) such as glass, crystal, metal, ceramic, vases, lamps, and even an entire window surface.