Temperature has the biggest influence on viscosity. At a certain temperature, also materials like slag (including coal ash), metals, and glass become liquid and can be processed as such. Viscosity measurements of these materials provide significant data to optimize energy-intensive production processes. Besides rotational tests to measure the viscosity, oscillatory tests are possible. They are used for differentiation between glass transition and crystallization, detailed characterization of melting behavior and solidification, and investigation of viscoelastic properties. For example, the faster the cooling, the lower the glass transition temperature for glass. The maximum temperature is 1800 °C.
Watch this 10-minute course to learn more about high-temperature rheology.