1, judging from the color and feel: gypsum powder with high whiteness is fine in fineness, good in quality and high in price, while gypsum powder with gray-black impurities is poor in quality. Rubbing gypsum powder with thumb and forefinger, the gypsum powder with rough feel has coarse fineness, poor quality and low price; Gypsum powder with delicate feel, fine fineness, good quality and high price. ?

2. Determine the setting time of stone powder: The setting time includes initial setting time and final setting time. The quality standard of setting time of gypsum powder is that the initial setting time is not less than 6min and the final setting time is not more than 25min under the standard consistency.

3. Determination of crystal water content: Gypsum powder is a crystal mixture, which contains gypsum, gypsum hemihydrate and anhydrous gypsum (calcined gypsum). In the process of frying, gypsum will appear in case of fire, or anhydrous gypsum will appear when the temperature is too high and the burning time is too long, which will affect the setting time of gypsum and the normal use of production.

Extended data:

Precautions:

1. Before construction, determine the verticality and flatness of the basement.

2. Do not mix mortar with water before use.

3. The mixed putty slurry should be used up within 1~2h (depending on the formula).

4. It should be polished within 1-2d.

5. When the base surface is calendered with cement slurry, it is recommended to use interface treatment agent or interface putty and elastic putty. White gypsum powder is the most common gypsum material, widely used in decoration, modeling, sculpture and other fields. Good white gypsum powder has high details and good hardness. Some also added a little calcium carbonate to achieve an extremely hard effect.

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