Calcium hydroxide is commonly used to prepare
lime mortar. One significant application of calcium hydroxide is as a
flocculant, in water and
sewage treatment. It forms a fluffy charged solid that aids in the removal of smaller particles from water, resulting in a clearer product. This application is enabled by the low cost and low toxicity of calcium hydroxide. It is also used in fresh-water treatment for raising the pH of the water so that pipes will not corrode where the base water is acidic, because it is self-regulating and does not raise the pH too much. Another large application is in the paper industry, where it is an intermediate in the reaction in the production of sodium hydroxide. This conversion is part of the
causticizing step in the
Kraft process for making pulp. In the causticizing operation, burned lime is added to
green liquor, which is a solution primarily of
sodium carbonate and
sodium sulfate produced by dissolving
smelt, which is the molten form of these chemicals from the recovery furnace. In
orchard crops, calcium hydroxide is used as a fungicide. Applications of 'lime water' prevent the development of cankers caused by the fungal pathogen
Neonectria galligena. The trees are sprayed when they are dormant in winter to prevent toxic burns from the highly reactive calcium hydroxide. This use is authorised in the European Union and the United Kingdom under Basic Substance regulations. Calcium hydroxide is used in dentistry, primarily in the specialty of
endodontics due to its antibacterial properties and induction of
hard-tissue deposition.
Food industry Because of its low
toxicity and the mildness of its basic properties, slaked lime is widely used in the
food industry, • In
USDA-certified food production in plants and livestock • To clarify raw juice from
sugarcane and
sugar beets in the
sugar industry (see
Carbonatation) • To process water for alcoholic beverages and soft drinks • To increase the rate of
Maillard reactions (e.g. in
pretzels) • In
pickling cucumbers and other foods • To make Chinese
century eggs • In maize preparation: removes the cellulose hulls of maize kernels (see
nixtamalization) • To clear a
brine of
carbonates of calcium and
magnesium in the manufacture of salt for food and pharmaceutical uses • As a calcium supplement in fruit drinks, such as orange juice, and
infant formula • As a substitute for
baking soda in making
papadam • In the removal of carbon dioxide from controlled-atmosphere produce storage rooms • In the preparation of mushroom-growing substrates
Native American uses In
Nahuatl, the language of the
Aztecs, the word for calcium hydroxide is . In a process called
nixtamalization,
maize is cooked with nextli to become
nixtamal, also known as
hominy. Nixtamalization significantly increases the bioavailability of
niacin (vitamin B3), preventing
pellagra. Nixtamal is also considered tastier and easier to digest. It is often ground into a flour, known as
masa, which is used to make tortillas and tamales, which cannot be done with non-nixtamalized maize. In chewing
coca leaves, calcium hydroxide is usually chewed alongside to keep the
alkaloid stimulants chemically available for
absorption by the body. Similarly, Native Americans traditionally chewed tobacco leaves with calcium hydroxide derived from burnt mollusc shells to enhance the effects. It has also been used by some indigenous South American tribes as an ingredient in
yopo, a psychedelic snuff prepared from the beans of some
Anadenanthera species.
Asian uses In South and Southeast Asia, calcium hydroxidelocally known by names including
chuna,
choona,
apog or
soonis typically added to a bundle of
areca nut and
betel leaf called "
paan" or
buyo to keep the
alkaloid stimulants chemically available to enter the bloodstream via
sublingual absorption.
Choona is a key ingredient in
Petha, contributing to its characteristic crunchy and firm texture. It is used in making
naswar (also known as
nass or
niswar), a type of dipping tobacco made from fresh tobacco leaves,
Choona, and wood ash. It is consumed most in the
Pathan diaspora in
Afghanistan,
Pakistan,
India and
Bangladesh. Villagers also use calcium hydroxide to
paint their mud houses in Afghanistan, Pakistan and India. Traditionally lime water was used in
Taiwan and
China to preserve
persimmon and to remove
astringency.
Hobby uses In buon
fresco painting, limewater is used as the colour solvent to apply on fresh plaster. Historically, it is known as the paint
whitewash. Limewater is widely used by marine aquarists as a primary supplement of
calcium and
alkalinity for reef aquariums.
Corals of order
Scleractinia build their
endoskeletons from
aragonite (a
polymorph of calcium carbonate). When used for this purpose, limewater is usually referred to as
Kalkwasser. It is also used in
tanning and making
parchment. The lime is used as a dehairing agent based on its alkaline properties.
Personal care and adornment Treating one's hair with limewater causes it to stiffen and bleach, with the added benefit of killing any lice or mites living there.
Diodorus Siculus described the
Celts as follows: "The Gauls are tall of body, with rippling muscles, and white of skin, and their hair is blond, and not only naturally so, but they also make it their practice by artificial means to increase the distinguishing colour which nature has given it. For they are always washing their hair in lime-water, and they pull it back from the forehead to the top of the head and back to the nape of the neck, with the result that their appearance is like that of Satyrs and Pans, since the treatment of their hair makes it so heavy and coarse that it differs in no respect from the mane of horses." Calcium hydroxide is also applied in a leather process called
liming. ==In stars==