Enamel/Mina is essentially glass which is ground to a powder before being fired on to a metal base. The ground glass is a combination of silica and soda ash with addition of small amount of metal oxides to give it colour. Firings can take from 30 seconds to several minutes, with the kiln heated between 650°C and 1000°C, depending on the techniques and materials used. Industrial, or liquid, enamels are enamel frits ground very finely and mixed with other components to make a liquid suspension. This is applied to a metal surface with a spray gun, a brush, or by dipping.