Gypsum powder (hereinafter referred to as semi-hydrated gypsum powder CaSO4.1/2H20, the same below) is widely used in ceramics forming consumption for its high quality, low cost, good activity after mixing with water, incomparable condensation, water absorption and easy processing properties, and is used to manufacture models of grouting, rolling and cold-forming.

　　石膏粉是由自然石膏矿物炒制加工而成。自然石膏是含有两个结晶水的硫酸钙矿物CaSO4·2H20。依据差热剖析，二水石膏在低温阶段有两个吸热反响。当温度为140℃左右时，其结晶水开端排出。在150℃～170℃时，很快合成为半水石膏(CaSO4·1/2H20)，当温度继续升高到225℃时，则失去全部结晶水，变成无水石膏(CaSO4)。

　　Gypsum powder is prepared by stirring natural gypsum minerals. Natural gypsum is a calcium sulfate mineral CaSO4.2H20 containing two crystalline water. According to differential thermal analysis, there are two endothermic reactions in dihydrate gypsum at low temperature. When the temperature is about 140 C, the crystal water is discharged at the beginning. When the temperature ranges from 150 to 170 C, it is quickly synthesized into hemihydrate gypsum (CaSO4.1/2H20). When the temperature continues to rise to 225 C, all crystalline water will be lost and anhydrous gypsum (CaSO4) will be formed.

　　石膏粉依据加工炒制工艺和产品晶型构造的不同可分为两种，即普通石膏粉（也叫β石膏粉）和高强石膏粉（也叫α石膏粉）。β石膏粉是在常压下凸底铁锅内160℃～170℃煅烧自然石膏粉料炒制而得；α石膏粉是将自然石膏块状料放在蒸压釜内，在130℃及1.5～3个大气压下蒸压3～5h加热加压脱水，然后150℃～170℃枯燥室内烘干，将其粉碎而得。 由于两种石膏粉的制造工艺不同，形成它们的晶型构造和产品性质不同。β石膏粉晶型构造是规则的片状晶体，晶粒的孔隙和裂纹较多

　　Gypsum powder can be divided into two kinds according to the different processing technology and product crystal structure, namely ordinary gypsum powder (also known as beta gypsum powder) and high strength gypsum powder (also known as alpha gypsum powder). Beta gypsum powder is prepared by calcining natural gypsum powder in a convex bottom iron pot at 160 ~170 C under atmospheric pressure; alpha gypsum powder is prepared by placing natural gypsum block material in autoclave, heating and dewatering under autoclave pressure for 3~5 hours at 130 ~1.5~3 atmospheric pressure, then drying in a drying chamber at 150 ~170 ~C and crushing it. The crystalline structure and product properties of the two gypsum powders are different due to their different manufacturing processes. The crystalline structure of beta gypsum powder is regular flake crystal, and there are many holes and cracks in the grain.

　　比外表积大，规范稠度需水量大，石膏粉与水混合后水化反响才能强，初凝时间短，模型的气孔率、吸水率高，但模型的强度低；而α石膏粉晶型构造是齐整的针状晶体，比外表积小，规范稠度需水量小，模型的气孔率、吸水率小，石膏粉与水混合后反响才能差，石膏浆体的活动性好，初凝时间长，模型强度高。依据这两种晶型石膏的特性，普通β石膏粉制造注浆成形模型，而α石膏粉制造滚压成形模型和塑压成形模型。

　　The water requirement of the standard consistency is larger than the surface area, the hydration reaction of the model is stronger after mixing gypsum powder with water, the initial setting time is shorter, the porosity and water absorption of the model are higher, but the strength of the model is lower; while the crystal structure of the alpha gypsum powder is a neat needle crystal, smaller than the surface area, the water requirement of the standard consistency is smaller, the porosity and water absorption of the model are smaller, and the reaction of the model after mixing gypsum powder with water is worse. The gypsum paste has good activity, long initial setting time and high model strength. According to the characteristics of these two crystalline gypsum, the grouting forming model is made of ordinary beta gypsum powder, while the rolling forming model and plastic forming model are made of alpha gypsum powder.

　　除了以上两种石膏粉外，消费中还运用由以上两种石膏粉按不同比例（普通是70%～80%的β石膏粉与30%～20%的α石膏粉）混匀构成的混合石膏粉。这种石膏粉是应用β石膏的吸水性能好和α石膏强度高的特性，用于陶瓷消费中注浆成形模型的制造（例如卫生陶瓷模型）。近些年来，随着陶瓷行业开展之需，在高强α石膏粉的根底上经过改良加工工艺和添加一些特殊外加剂又衍生出许多有特殊用处的超高强石膏粉，如母模石膏粉、K型粉、树脂石膏粉等等。

　　In addition to the above two kinds of gypsum powder, mixed gypsum powder composed of the above two kinds of gypsum powder in different proportions (usually 70%-80% of beta gypsum powder and 30%-20% of alpha gypsum powder) is also used in consumption. This kind of gypsum powder is applied to the manufacture of grouting forming models (e.g. sanitary ceramics models) in ceramic consumption because of its good water absorption performance of beta gypsum and high strength of alpha gypsum. In recent years, with the development of the ceramic industry, many super-high strength gypsum powders, such as mother mould gypsum powder, K-type powder, resin gypsum powder and so on, have been derived from high strength alpha gypsum powder by improving processing technology and adding some special additives.