An important mold made of plaster. A plaster mold is made by first making the required mold with clay, stone, or oil clay, then pouring water into a bowl and spreading gypsum plaster over it to make plaster mud, pouring it over the mold, waiting for it to harden, and then removing it from the mold. This is called a mother mold. In this case, the mold is divided into two or more pieces depending on the shape of the prototype. If the mother mold is molded again with plaster, a plaster mold equal to the original mold is obtained. This is called the original mold. When plaster mud is poured over the plaster mold, a release agent such as a solution of potash soap or boiled olive oil is applied in between to prevent binding of the plaster to the plaster. Molds made in this way are classified into several types according to the purpose and method of use. There are three types of molds: wheel-thrown molds, raised molds, and cast-in-place molds.
Wheel-Thrown Mold】This type of mold is used for the machine wheel and is available in large and small, deep and shallow, circular and oval shapes. The plaster mold is placed on the potter’s wheel head and kneaded clay is pressed onto the mold, and the moldboard support is lowered to allow the clay to be scraped to the required thickness. There are many shapes and types of molds, and most of them are not circular.
There are two types of making molds: stroking molds and aggressive molds.
The clay is cut into a flat plate of the required thickness, placed on the mold, and moistened with a piece of cloth or a sponge, and stroked from above to adhere it equally to the mold. The mold used for this method is called an attack mold.
Casting molds: These molds come in a variety of shapes, but most are medium-sized and can also be used to cast dishes. This type of mold utilizes the water-absorbing action of plaster. When mud plaster is injected into the mold, the part attached to the plaster absorbs the water and the clay adheres to the plaster surface. The same principle is used to make plaster molds. The same principle can also be applied to plaster molds by immersing them in plaster.
