Saltern is a word with a number of differing (but interrelated) meanings. In English archaeology, a saltern is an area used for salt making, especially in the East Anglian fenlands.
The term saltern also describes modern salt-making works, and contain hypersaline waters that usually contain high concentrations of halophilic microorganisms, primarily haloarchaea but also other halophiles including algae and bacteria. Salterns usually begin with seawater as the initial source of brine but may also use natural saltwater springs and streams. The water is evaporated, usually over a series of ponds, to the point where NaCl and other salts precipitate out of the saturated brine, allowing pure salts to be harvested. In England, complete evaporation in this fashion was not routinely achievable and salt from the concentrated brine was produced by boiling the brine.
Earliest examples of pans used in the solution mining of salt date back to prehistoric times and the pans were made of ceramics known as briquetage. Later examples were made from lead and then iron. The change from lead to iron coincided with a change from wood to coal for the purpose of heating the brine. Brine would be pumped into the pans, and concentrated by the heat of the fire burning underneath. As crystals of salt formed these would be raked out and more brine added. In warmer climates no additional heat would be supplied, the sun's heat being sufficient to evaporate off the brine.