Gypsum plasters. I. Preparation of β‐hemihydrates

Abstract β‐Hemihydrate plasters were prepared in one way by continuous heating of gypsum at 90 °C. In addition to this, a new attempt has been made to prepare this material by making use of the phenomenon of rehydration of γ‐anhydrite. The hemihydrate formation, in both methods, was followed through periodical differential thermal analysis studies. Results showed that 4 days heating at 90 °C, as well as the rehydration of γ‐anhydrite at room conditions for 30 days, result in the formation of pure hemihydrate. The prepared plasters were found to be free from gypsum.