Sea Salt Production
Sea salt is produced by the natural evaporation of seawater. Salt water is captured in a series of successive ponds and allowed to evaporate through the action of the sun and wind. This process can take from one to five years. Since evaporation rates must exceed the amount of rainfall for these solar salt plants to succeed, sea salt production is typically located in areas of low rainfall.
Seawater contains approximately 3.5% total dissolved minerals of which sodium chloride is 77%, or about 2.7% of seawater. The other 0.8% consists primarily of calcium, magnesium and sulfate ions. Salt works, therefore, extract just 2% of the seawater in their ponds as salt. As a result, large tracts of low lying marsh lands are often required for the “farming” or production of sea salt.
The evaporation ponds will often have distinct colors. They can appear grey, pink or even red. Their color depends on the level of salt and trace minerals in the water, also called brine, as well as what species of plants and animals make their home in the ponds. It is the trace minerals and nutrients in sea salt that gives them their distinct flavor, which can range from sweet and creamy to slightly bitter. Increasingly, gourmet chefs have come to appreciate and distinguish between the many varieties of sea salt and how their unique flavor characteristics can enhance the flavor and finish of food.
Salt crystals begin to form in the evaporation ponds when the brine concentration reaches 25.8 % sodium chloride. Today, most sea salts are harvested mechanically, though certain artisan salts are still harvested by hand. The best known example of hand harvesting occurs in the salt ponds of Guérande, France where long narrow basins are used as evaporation ponds. This enables an artisan Paludier (craftsman salt harvester) to "sweep" the top of the evaporating sea water with a rake and harvest the precious Sel Gris de Guérande (hand harvested sea salt with a grey cast).
When the salt is mechanically harvested, after the salt "crop" reaches the appropriate depth, equipment is used to collect the salt. The salt is typically washed using clean brine (fresh water and dissolved salt) to remove small amounts of impurities. Depending on its final use the salt is crushed, screened and dried in kilns or fluidized-bed dryers.