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==Limewater==
'''Limewater''' is a saturated aqueous solution of [[calcium hydroxide]]. Calcium hydroxide is sparsely soluble at room temperature in water (1.5 g/L at 25 °C<ref>'Solubility of Inorganic and Metalorganic Compounds – A Compilation of Solubility Data from the Periodical Literature', A. Seidell, W. F. Linke, Van Nostrand (Publisher), 1953 {{ISBN?}}</ref>). "Pure" (i.e. less than or fully saturated) limewater is clear and colorless, with a slight earthy smell and an astringent/bitter taste. It is basic in nature with a [[pH]] of 12.4. Limewater is named after [[limestone]], not the [[Lime (fruit)|lime fruit]]. Limewater may be prepared by mixing calcium hydroxide (Ca(OH)<sub>2</sub>) with water and removing excess undissolved solute (e.g. by filtration). When excess calcium hydroxide is added (or when environmental conditions are altered, e.g. when its temperature is raised sufficiently), there results a milky solution due to the homogeneous suspension of excess calcium hydroxide. This liquid has been known traditionally as '''milk of lime'''.
==Applications==
===Arts===
In buon [[fresco]] painting, limewater is used as the colour solvent to apply on fresh plaster. Historically, it is known as the paint [[whitewash]].
[[File:Dying Gaul (casting in Pushkin museum) 04 by shakko.jpg|thumb|Closeup of cast of ''The Dying Gaul'', showing distinctive hairstyle, supposedly derived from washing in limewater.]]
=== 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:
"Their aspect is terrifying... They are very tall in stature, with rippling muscles under clear white skin. Their hair is blond, but not only naturally so: they bleach it, to this day, artificially, washing it in lime and combing it back from their foreheads. They look like wood-demons, their hair thick and shaggy like a horse's mane. Some of them are clean-shaven, but others – especially those of high rank, shave their cheeks but leave a moustache that covers the whole mouth...".<ref>{{Cite web|url=http://exploringcelticciv.web.unc.edu/diodorus-siculus-library-of-history/|title = Diodorus Siculus, Library of History | Exploring Celtic Civilizations}}</ref><ref>{{cite web|url=https://penelope.uchicago.edu/Thayer/E/Roman/Texts/Diodorus_Siculus/5B*.html|title=Diodorus Siculus – Book V, Chapter 28|website=penelope.uchicago.edu|language=english|access-date=2017-11-12}}</ref>
=== Food preparation ===
Limewater is used in the preparation of maize for [[corn tortillas]] and other culinary purposes using a process known as [[nixtamalization]]. Nixtamalization makes the [[niacin]] nutritionally available and prevents [[pellagra]].<ref>{{cite journal |url=https://www.researchgate.net/publication/228453826 |title=Nixtamalization, a Mesoamerican technology to process maize at small-scale with great potential for improving the nutritional quality of maize based foods |last=Wacher |first=Carmen |date=2003-01-01 |journal=Food Based Approaches for a Healthy Nutrition in Africa |url-status=live |archive-url=https://web.archive.org/web/20180305202539/https://www.researchgate.net/publication/228453826_Nixtamalization_a_Mesoamerican_technology_to_process_maize_at_small-scale_with_great_potential_for_improving_the_nutritional_quality_of_maize_based_foods |archive-date=2018-03-05}}</ref> Traditionally lime water was used in [[Taiwan]] and [[China]] to preserve [[persimmon]] and to remove [[wikt:astringency|astringency]].<ref>{{Cite book |last=Hu |first=Shiu-ying |url=https://www.worldcat.org/oclc/58840243 |title=Food plants of China |date=2005 |publisher=Chinese University Press |isbn=962-201-860-2 |location=Hong Kong |oclc=58840243}}</ref>{{Rp|page=623}}
===Other uses===
Limewater is widely used by marine aquarists as a primary supplement of [[calcium]] and [[alkalinity]] for reef aquariums. [[Coral]]s of order [[Scleractinia]] build their [[endoskeleton]]s from [[aragonite]] (a [[Polymorphism (materials science)|polymorph]] of calcium carbonate). When used for this purpose, limewater is usually referred to as ''Kalkwasser''. It is also used in [[tanning (leather)|tanning]] and making [[parchment]]. The lime is used as a dehairing agent based on its alkaline properties.<ref>''The Nature and Making of Parchment'' by Ronald Reed {{ISBN?}}</ref>
Calcium hydroxide is also applied in a leather process called [[Liming (leather processing)|liming]].
==Health risks==
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