In inorganic material components can be contained in that are volatile at high temperatures. This characteristic is typical for carbonates and organic contaminations. The proportion of these substances is extremely important for the planning and performance of molten glass.
It can be ascertained in the laboratory based on the mass loss during annealing. Common annealing temperatures reach from 550 °C to 1200 °C.
(Samples: powdered samples or granulates)