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Gypsum is a mineral composed primarily of calcium sulfate. In this article, we will introduce the uses of gypsum.
Gypsum has been used in many sculptures since ancient times. However, since it dissolves in water, it is mainly used for indoor sculptures. Today, it is used to make replicas of works of art and model sculptures for art students. Reproductions of Michelangelo's David, for example, are also made of plaster.
Gypsum is excellent in fire resistance and soundproofing, so it is often made into boards and used in construction as plasterboard. Incidentally, plaster sand does not get hot even when exposed to the sun during the day.
A cast, used to immobilize a broken arm, is made of a bandage containing baked plaster. Baked plaster bandages came into use in the 1800s and have since become the standard method of treating fractures.
Bittern is often used as a coagulant for tofu. There are many other coagulants, one of which is calcium sulfate, made from gypsum. Nigari, which is derived from seawater, has often been used as a coagulant for tofu in Japan, which is surrounded by the sea. However, after Japan entered World War II, bittern was procured for military use. This was because the magnesium chloride contained in nigari was needed for metalworking in the manufacture of fighter planes and other aircraft, and was designated as a military material.
As a result of this background, bittern for tofu became scarce, and calcium sulfate was used as a substitute. Today, calcium sulfate is not often used as a coagulant because bittern derived from the sea seems to be healthier.
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