More water. Because too much water is added, the plaster image is not firm, the plaster will crack if it is too thin, and it will be broken and easy to crack when it comes out of the mold. Gypsum paste can't stick to the mold when adding too much water for the first time, and it won't flow after a long time, forming some places thick and some places thin. Gypsum is a monoclinic mineral and a hydrate with calcium sulfate (CaSO4) as the main chemical component. Gypsum is a widely used industrial and building material.