Conclusions:
(1) The mixture of ordinary gypsum and ultra anhydrite at different water temperatures had no noticeable impact on the size of the plaster models—the latter had good dimensional stability. Temperatures between 0℃-30℃ are suitable for stir-mixing gypsum.
(2) Ordinary gypsum mixed at different water temperatures had a noticeable impact on the plaster models’ resistance to compression and bending. At the temperature range of 0℃-30℃, the resistance to compression and bending strength was 0.5h< 1h< 6h< 24h. The 15℃ group's resistance to compression and bending was the highest.
(3) Ultra anhydrite mixed at different water temperatures had a noticeable impact on the plaster models’ resistance to compression and bending. At the temperature range of 0℃-30℃, the resistance to compression and bending strength was 0.5h< 1h< 6h< 24h. The 15℃ group's resistance to compression and bending was the highest.