Salt production is one of the oldest chemical practices performed by man. Although salt is produced naturally when seawater evaporates, the process can easily be reproduced to create a higher yield. Some salt is still produced using ancient methods, but new, faster, and less expensive methods have been developed. Depending on the source of the salt and the technique used to create it, the end product will have different flavors and textures.
Today there are three main methods for obtaining salt:
- Evaporation from sea water
- Mining salt from the earth
- Creating salt brines
Most common table salts are a product of salt brines, while specialty or gourmet salts are still produced via evaporation of seawater; salts used for industrial purposes are obtained through mining. China is the largest producer followed by the United States. Of the 220 million tons of salt, only 6% is used for human consumption.
Salt accounts for about 3.5% of the world's oceans. It is naturally produced when shallow ponds and bays dry up in the sun and the wind and large salt crystals are left behind where the salty water once was. When producing sea salt on an industrial scale, seawater is placed in large "concentrating ponds" to allow efficient evaporation from the sun and the wind. The manufacturing of sea salt can only be performed in areas with low rainfall in order for enough time to pass for evaporation. For this reason, sea salt is often produced in dry climates such as the Mediterranean and Australia.
Sea salt is also produced on a much smaller scale and by ancient, skilled techniques. Fleur de sel is an example of an artisan salt that is still, to this day, produced by old-fashioned methods. This light, flaky salt is manufactured in small ponds in France and is only made during the summer months of May to September.
Rock salt (also known as halite) is present in the rocky under layers of the Earth's surface and can be extracted through deep-shaft mining. These large deposits of salt are the result of ancient underground waterways that have long since dried up.
Rock salt is extracted through dynamite, similar in fashion to the mining of any other mineral. Once it is brought to the Earth's surface, it is crushed and used for industrial and other non-food purposes. This type of salt contains many minerals and other impurities.
While the ocean is a natural salt brine, hydraulic mining (or solution mining) of salt involves pumping water below the earth's surface to dissolve salt deposits and create a salt brine. This brine is then pumped to the surface and evaporated to create salt. The salty brine may be treated prior to evaporation to reduce mineral content, yielding a nearly pure sodium chloride crystal. This method is inexpensive, has a high yield, and produces a very clean salt. Most table salt is produced with this method.