Casting isotherm powder is added on top of the steel melt inside the ladle. It then covers the top of the melt, mostly on melted, and serves the following purposes:

1. Thermal insulation by reducing the escaped heat from the steel melt surface. This, in turn, leads to increased refractory durability and improved casting by increasing controllability.
2. Preventing further oxidation of steel.
3. Absorbing the non-metallic impurities.