Glass

Glass is a unique material to measure as the glass itself is similar to honey – its viscosity changes dramatically with a change in temperature. Temperature is critical for the forming process because, in this temperature range (about 2000°F / 1100°C), the viscosity of glass changes by 30% with a temperature change of only 1°C. Like honey, when glass is warm it can flow like water and when it is cold it is solid as a rock. As it is cooled from its liquid state, it gradually becomes thicker and thicker and it resists flow gradually more and more. As a result, for many forming processes, the process is often controlled to a fraction of a degree.