Sea salt is salt that is produced by the evaporation of seawater and saltwater. It is used as a seasoning in foods, cooking, cosmetics and for preserving food. It is also called bay salt, solar salt, or simply salt. Like mined rock salt, production of sea salt has been dated to prehistoric times.
Commercially available sea salts on the market today vary widely in their chemical composition. Although the principal component is sodium chloride, the remaining portion can range from less than 0.2 to 10% of other salts. These are mostly calcium, potassium, and magnesium salts of chloride and sulfate with substantially lesser amounts of many trace elements found in natural seawater. Though the composition of commercially available salt may vary, the ionic composition of natural saltwater is relatively constant.
Sea salt is mentioned in the Vinaya Pitaka, a Buddhist scripture compiled in the mid-5th century BC. The principle of production is evaporation of the water from the sea brine. In warm and dry climates this may be accomplished entirely by using solar energy, but in other climates fuel sources have been used. Modern sea salt production is almost entirely found in Mediterranean and other warm, dry climates.
Such places are today called salt works, instead of the older English word saltern. An ancient or medieval saltern was established where there was:
Access to a market for the salt
A gently shelving coast, protected from exposure to the open sea
An inexpensive and easily worked fuel supply, or preferably the sun
Another trade, such as pastoral farming or tanning—which benefited from proximity to the saltern (by producing leather, salted meat, etc.) and provided the saltern with a local market
In this way, salt marsh, pasture (salting), and salt works (saltern) enhanced each other economically. This was the pattern during the Roman and medieval periods around The Wash, in eastern England. There, the tide brought the brine, the extensive saltings provided the pasture, the fens and moors provided the peat fuel, and the sun sometimes shone.