CA-D1, dihydrate calcium sulfate is produced from the processing of
naturally occurring gypsum mineral, white gypsum containing about
20% water of crystallization. Depending upon vapor pressure,
relative humidity, loading levels, etc., this water of
crystallization, or combined water as it is often called, starts
being released as the filler is heated above ~50 °C. By about 180
°C, 75% of the combined water has been released. Water is not
totally removed until temperatures exceed 400 °C.