Grouting is the earliest molding method used for alumina ceramics. Due to the use of plaster molds, the cost is low and it is easy to form large-sized, complex-shaped parts. The key to grouting is the preparation of alumina slurry. Generally, water is used as the flux medium, and then a degumming agent and a binder are added. After being sufficiently ground, the air is exhausted, and then poured into a gypsum mold. Due to the adsorption of moisture by the capillary of the plaster mold, the slurry was solidified in the mold. During hollow grouting, when the slurry on the mold wall absorbs the slurry to the required thickness, the excess slurry must be poured out. In order to reduce the shrinkage of the green body, high concentration slurry should be used as much as possible.