Calcium hydroxide or slaked lime is an inorganic compound with the chemical formula Ca(OH)2. It is a colorless crystal or white powder and is obtained when calcium oxide (called lime or quicklime) is mixed, or slaked with water.
Calcium hydroxide, informally referred to as slaked lime, is a compound created through the mixture of calcium oxide with water. The resultant substance is a white powder or crystal compound with strong alkaline properties. Calcium hydroxide has widespread uses, including applications in dental work, hair care products, leather production, food manufacturing and others.
According to the National Institutes of Health, calcium hydroxide is commonly used in dental work as an antimicrobial, and is the substance of choice for forming a protective layer known as an apical barrier. Apical barriers are sometimes employed as a means of warding off pulp necrosis in situations when endodontic surgery would be especially difficult, often the result of an immature permanent tooth. Since calcium hydroxide can help disinfect a tooth where an infection already exists, it may be used as a short-term treatment for reducing pain and swelling in preparation for endodontic surgery.
Absolute Astronomy states that calcium hydroxide is used as the active alkaline ingredient in some hair relaxer products. Hair relaxers are creams or liquids that are designed to straighten curly hair when applied, and many of these products contain lye, a powerful caustic. Lye poses a certain risk of hair and skin damage, however, so some hair product manufacturers have created no-lye versions that use calcium hydroxide in its place. According to the Cornell Center for Materials Research, calcium hydroxide can straighten curly hair because it breaks down the sidulfide bonds that connect cysteines, the amino acids that are present in higher concentrations in naturally curly hair. Breaking these bonds and sealing them off with calcium hydroxide permanently alters the physical structure of the treated hairs.
Calcium hydroxide makes an effective solution for separating hair from animal hides in preparation for the production of leather, according to Van Dyke's Taxidermy. A mixture of calcium hydroxide and warm water creates a bath in which freshly fleshed hides should be soaked for up to four days, and stirred frequently. This process loosens the hair and fur to the point that it can usually be removed by hand. After all of the hair has been removed with hands or fleshing tools, the hides must be rinsed thoroughly and steeped in an ammonium sulfate bath to halt the calcium hydroxide's caustic lime action and balance the pH.
Absolute Astronomy states that calcium hydroxide is used in the processing of some soft drinks and alcohol beverages. It is also commonly used in the processing of Lutefisk, a traditional Swedish dish. Lutefisk, according to the Nordic Recipe Archive, is a stockfish that is soaked in cold water for several days, then soaked in a combination of water and lye or another harshly caustic substance like calcium hydroxide. This soaking cycle breaks down the proteins, resulting in a delicate fish with a jelly-like consistency. It also makes the fish caustic, so several additional days of soaking in water, changed daily, is required before the fish can be eaten.