(1) model and release agent model can be made of metal, rubber, wood, etc. And the wooden pattern must be painted first to prevent water seepage and adhesion. The release agent includes stearic acid, vaseline and silicone grease dissolved in lamp oil.

(2) If pure water or water with similar properties is used as mixed water and stirring water, the mixed water of gypsum powder hemihydrate is 30-35%, and the mixture is stirred evenly in a container with spiral blades to form emulsion slurry.

During the period when the slurry has enough fluidity, it is poured into the molding frame together with the model, and it is slightly vibrated or decompressed and defoamed with10-1torr to avoid air bubbles from adhering to the surface of the model. At this time, gypsum hemihydrate generates water and reacts, and the viscosity of slurry increases, losing fluidity, setting and hardening, forming gypsum dihydrate, which heats up with the growth of crystals, causing condensation and expansion.

(3) Gypsum drying is the most time-consuming and important step in the whole project. Rapid heating will cause the mold to crack. Therefore, it is necessary to set several drying temperatures and slowly raise the temperature. The final drying temperature is 200 ~ 230℃, and the mold is dehydrated to form anhydrous gypsum. It is best to use an automatic temperature-controlled hot air forced circulation exhaust electric drying furnace. The temperature distribution in the furnace is uniform and the drying time is shortened. Even if the final drying temperature is set directly, the mold is rarely broken.