[Study on gypsum hardener].

The purpose of this study was to search for an appropriate condition for shortening the treatment time of gypsum hardener, Plaster Aid. In order to keep the increased strength of plaster with this new hardener, compressive strength and dimensional change in various conditions of heating temperature, heating time and drying time were examined. The following results were obtained. 1. High compressive strength was maintained in the condition of 70 degrees C of heating temperature, with more than 15 minutes of heating time and more than 15 minutes of drying time. In this condition up to 90 minutes could be saved in comparison with the conventional method. 2. Plaster models had a tendency to shrink in the condition of 70 degrees C of heating temperature.