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How Sea Salt Is Made

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A bowl of sea salt.

Salt is used for very many purposes both as an additive to food and for a wide variety of industrial processes. Nowadays, sea salt has assumed a certain superiority over the cheaper, common table salt for cooking and seasoning. Some people think it has a better flavour, others consider that the additional minerals it contains make it better for one's health. Is it really made out of the sea? Yes it is, but the question is 'How'?

Sea Salt, Table Salt and Rock Salt

Three major ways that salt are obtained are:

From the sea - 'sea salt1'. This is primarily used for cooking, seasoning and curing traditional foods such as fish or pork with salt. Often sea salt is sold in large crystals, which may need to be ground before use at the table, but you can also find a finer variety.

From underground by mining - this is 'rock salt'. If the mine contains very pure salt deposits, then this form of rock salt is excellent for culinary use, and is often used in a salt grinder2 at the table. If the natural rock salt in the mine is mixed with insoluble compounds, impurities or other chemicals then it is often used as salt for gritting the roads during winter.

From underground by solution mining, or brine extraction. This produces pure sodium chloride, which is made into table salt. Because it has a fine flowing nature and tiny crystals it can be used straight from a salt cellar. Often it is iodised3. The pure sodium chloride produced this way is also used in countless industrial processes.

Salt is also produced from salt lakes such as the Great Salt Lake in Utah.

The Earth's oceans are salty and contain billions and billions of tons of dissolved salt, sodium chloride. They also contain other soluble salts of minerals such as calcium, magnesium and potassium. The exact chemical composition varies according to the precise region of the ocean in question. Sea salt production is usually in regions with high sunshine levels and low rainfall.

Next time you take a trip to the sea-side, particularly if you have young children with you, collect a bottle full of sea water. Take it home and try leaving a shallow dishful for a week or so uncovered in a warm room. After a while you should see a white substance appear around the edge of the water and at the bottom of the dish. As the sea water dries up, the dissolved salt is deposited on the dish. You are making your own sea salt4!


In the days before refrigeration, salt was one of the most reliable ways5 to preserve food, especially meat or fish. Salted meat and fish can last for many months, can be taken on long journeys or kept in warm conditions where bacteria would otherwise spoil the food. Salt was an expensive commodity and was used as a currency in earlier times, particularly on trading routes in the ancient world. It was also known as 'white gold'. A Roman soldier's pay was called 'salarium', from the Latin 'sal' for salt, because the soldiers used it to buy salt. Our word 'salary' comes from this.

In the case of salted fish, for instance, cod was frequently caught thousands of miles away from the fishermen's home ports - the men would be away for many weeks. In the days before refrigeration it was necessary to salt the catch immediately it was pulled from the sea. Salt cod became a staple food of many a distant colonial island and apparently helped conquer the Americas.

Sea salt was very often produced in areas where fishing was prevalent, where the coast line provided suitable natural conditions.

Historical and Geographical Methods Contrasted

Sea salt is harvested in many places worldwide such as the Île de Ré in France, the Mediterranean, San Francisco Bay and Cape Cod, USA and from the Great Australian Bight. The Dead Sea is also famous for various salt products emanating from the region. Three contrasting places have been selected to show some different methods in sea salt manufacture.

Sea Salt Production in Lanzarote, Canary Islands, Spain

The Salinas de Janubio, Lanzarote.

Salt has been continuously harvested on a commercial scale on the island of Lanzarote since the 16th Century. It was traditionally used to support the fishing fleet which would be away from the islands for months at a time, fishing along the African coast as far down as the equator. On the outward leg the holds would be laden with local sea salt which was used to preserve the catch and keep it in good condition for the journey home.

The production method took advantage of natural shallow sea lagoons. These were improved by creating small patchworks of salt ponds which were filled using water pumped from the sea by small windmills, many of which can still be spotted when driving around the island. The water in these saline ponds is allowed to evaporate in the hot dry atmosphere; Lanzarote has very little annual rainfall and has low humidity. The island also has year-round sub-tropical sunshine. As the salt water in the ponds becomes more concentrated, salt crystals begin to form in a layer at the bottom. The salt workers use traditional wooden scrapers to draw the salt crystals to the edges, where they are raked together into mounds to continue to dry out some more in the hot sun.

The Salinas de Janubio is the last remaining saltworks in production on the island of Lanzarote. At one time salt production was the most lucrative economic occupation on the island, when salt was needed for food preservation. With the advent of refrigeration, and particularly with the advent of refrigerated fishing vessels, the export of salt from the island fell, and with it the old salinas6 fell into disrepair. At the time of writing this Entry, there have been proposals to improve facilities at the Salinas de Janubio in order to allow tourists to visit and learn about salt production on the island. The oldest salinas in the Canary Islands can be found at the very northernmost tip of Lanzarote, where they can still be seen when visiting Mirador del Rio. This saltworks was started in 1520 by the first Spanish Governor of the Canary Islands, Sancho de Herrera. It is no longer in production.

During the three years of the Spanish Civil War from 1936 the Canary Islands were left to their own devices and times were very hard for the indigenous community. There was much poverty and deprivation; salt production became one of the only sources of income for many of the islanders. Almost as soon as the Civil War was over the Second World War began, and the Islands once more became cut off, as they were considered a strategic land mass. A blockade prevented supply ships from sailing between them and the Spanish mainland. The islanders once again had to rely on their own resources throughout this period. Salt was an essential requirement in preserving the catches of fish which made up a vital part of the local diet.

In the period immediately following World War II the islands were able to cash in on the demand for salt, due in part to the destruction of European industries that traditionally supplied the commodity. However, once the European sources of salt regained full productivity, demand for Canarian sea salt fell once more and the islanders' production of it tailed off dramatically. The old salinas became abandoned and derelict.

In the 1970s there began a process of encouraging tourism, and it is the tourist economy on which the islands now depend for much of their livelihoods. Many of the old salinas fell into disrepair. The first 5-star hotel was built on the site of a saltworks outside the then village of Costa Teguise. The architect, Fernando Figueras, used the shape of salt crystals for the inspiration for his design, which can best be appreciated from the air. The influential artist César Manrique designed the ground, garden and pool. The hotel was named Las Salinas as a reminder of where it had been built.

Sea Salt Production in Essex, England, UK

Salt production has been carried out on the Essex coast for 2,000 years. There were two reasons why this coastline was used for salt-making; a comparatively low local rainfall and the fact that salt marshes make the tidal waters have a high saline content. At high tide the marshes are covered in seawater; when the tide recedes the salt deposits are left on the drying vegetation and estuary mud. At the following high tide this 'extra' salt is re-dissolved into the tidal waters, thus giving a better concentration of salt per litre than ordinary seawater.

The method used in antiquity was to allow the tidal rivers to flood basins cut into the clay, which were dammed and then allowed to evaporate naturally. After some time, water from the saline ponds was collected and put into clay pots which were then boiled over fires. When the process was complete the pots had to be broken open to remove the salt.

The Maldon Salt Company is probably the best known English sea salt having produced this commodity for the last two hundred years. Other companies which traditionally used to make salt in this region have ceased trading, because of the competition from cheaper sources, such as the Cheshire Salt mines.

Modern production uses a pipeline, which draws in water from the centre of the River Blackwater during the period when the salinity is at its highest. The water is pumped into large settling tanks, allowing sediments, mud and other impurities to sink to the bottom. The clean portion of the water is then drawn off and transferred into shallow, open, stainless steel pans which are heated to boiling point and the process of salt crystalisation is begun. To begin with, the magnesium salts float to the surface in a form of a scum. These are removed by skimming the surface. (Magnesium salts can give the finished product a bitter taste.) Next, the heat source is adjusted so that the sodium chloride crystals gently begin to form. The water is evaporated at a rate which allows layers of sodium chloride crystals to form at the bottom of the pans. As more and more water is lost by evaporation the level of the liquid falls and salt crystals begin to form on the surface of the liquid as well. Eventually these become large enough to sink to the bottom. Once a critical amount of sea salt crystals has formed, they are scooped out and allowed to drain. Once they are dry they can be packaged for sale.

Guérande, France

At the mouth of the Loire river, on the west coast of France, lies the small town of Guérande. Here, the world famous 'Fleur de Sel' is hand harvested from the extensive salt lagoons of the salt marshes. Fleur de sel literally means flower of salt, and describes the filigree fine crystals of delicate white salt.

If one studies satellite images of the area, these salt lagoons can clearly be seen, making a patchwork of irregular white rectangles between the meandering waterways of the tidal estuaries. This is where, for countless centuries, the work of harvesting the precious commodity of salt has taken place. These traditional collection methods have continued unchanged right up to the present day. Since the 10th Century, the work of the artisan paludiers7 has been carried out with the same gentle precision. At high tide, seawater is guided into the network of small salt ponds by means of a system of gates and dams through various winding waterways. As the water reaches further into the system it becomes gradually more and more concentrated with salt, due to the process of natural evaporation in the warm summer sun. As the brine becomes saturated and the level of water falls to approximately 1cm, salt begins to crystalise on the top of the ponds. This usually takes place when there is a drying wind from the east. These crystals, being large and flat, 'grow' as they float on the surface. This is the point where the skilled workforce act, and using wooden hand rakes, they scoop these fleur de sel crystals to the side of the ponds where they are left to dry. This is very delicate work, and so as not to break the fragile crystals it was traditionally regarded as an occupation for women.

The fleur de sel is carefully packaged so as to retain the fine crystal structure. Due to the small amount of salt that can be harvested by these means, the fleur de sel is much more expensive than other forms of sea salt. Sometimes the resulting salt is a very pale pink in colour, due to minute traces of marine microalgae.

'Grey' sea salt is also harvested from the same ponds, by scraping up the larger crystals of salt that form at the base of the ponds. It is slightly off-white in colour, due to the natural additional minerals it contains. In the summer months, 50kg of this coarse sea salt can be harvested per day from a single salt pond compared to less than one kilogram of fleur de sel. These comparative differences in harvesting figures mean that the price differences of the two sorts of salt from the same region are quite marked. It is recommended that the coarse salt is used for cooking and the fleur de sel is used for 'finishing', ie garnishing and for the table.

Recipes using Sea Salt

If you should go to a restaurant in the Canary Islands you will notice that there is often a dish on the menu called 'Canarian Potatoes'. These are locally grown arrugar potatoes (very small potatoes, akin to British new potatoes in size). They were traditionally cooked by boiling them in seawater. This was because the annual rainfall was so very limited that it was useful to conserve as much drinking and cooking water as possible. Nowadays the potatoes are not cooked in sea water, but the tradition continues by the following method of preparation of Canarian potatoes.

The potatoes are washed, and with the skins left on, they are boiled in water until cooked. They are then drained and dipped into a very strong solution of salty water. The potatoes are drained once again and set to dry in an oven, the salt dries on the potato skins in a white layer and their skins turn wrinkly. The potatoes are served with various local salsas, or mojo sauces, made either from parsley and avocado (mojo verde) or pimento and paprika (mojo rojo) or alioli.

Another traditional dish from various parts of the world is to bake a whole fish in a mound of sea salt. A large cleaned fish, such as a Sea Bass, is laid on a baking tray on which a layer of sea salt has been placed. The fish is then covered with a top layer of salt, until it is entirely covered. The fish is placed into a very hot oven. When it is cooked, it is brought to the table, doused in spirits such as Pernod, set alight and then portioned and served by the head waiter. It would be imagined that the resulting fish would be salty, but this is not at all the case. The fillets of fish are served without skin or bone to the diners and are succulent and moist, tasting only of freshly-caught, delicate fish.

1Often known as 'Bay' salt or solar salt in the USA.2As opposed to a pepper mill.3To prevent illness in some parts of the country where people do not obtain enough iodine naturally in their diet, and also to prevent the salt from clumping together.4It is not actually recommended that you consume this salt.5Other ways to preserve food are air drying, smoking, pickling or conserving in sugar.6Saltworks.7The local French term for the salt harvesters.

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