The ancient chemical that shaped civilizations and even bleached Celtic hair
From the nixtamalization of Aztec maize to the heavy, blonde manes of the ancient Gauls, calcium hydroxide has been a silent architect of human culture for millennia. This versatile white powder does far more than just hold bricks together; it alters biology, preserves food, and even transforms the chemistry of our most traditional stimulants.
Known variously as slaked lime, hydrated lime, or 'nextli' in Nahuatl, calcium hydroxide is an inorganic compound produced by mixing quicklime with water. This exothermic reaction is one of humanity's oldest known chemical processes, with evidence of production dating back to at least 7000 BCE. Its utility spans the spectrum from heavy industry to the dinner table, with an annual global production of approximately 125 million tons.
In the Americas, the Aztec process of nixtamalization uses calcium hydroxide to cook maize kernels. This crucial step removes cellulose hulls and significantly increases the bioavailability of niacin (vitamin B3), which prevents the disease pellagra. It also creates the dough, or masa, essential for making tortillas and tamales. Similarly, in South and Southeast Asia, the substance (known locally as chuna or soon) is added to 'paan' to ensure alkaloid stimulants in betel leaves are chemically available for absorption through the bloodstream.
The compound's reactive properties have also left a mark on history and aesthetics. The ancient historian Diodorus Siculus noted that the Celts used limewater to bleach and stiffen their hair, a practice that left their manes looking as coarse as horses. In modern dentistry, since 1920, it has been used in root canal fillings due to its antibacterial properties. Beyond biology, it serves as a vital industrial tool: it acts as a flocculant in sewage treatment, a neutralizing agent for acid rain, and a key component in the Kraft process for paper production.
Source: Calcium hydroxide
