Thursday, 19 April 2007

more about salt

Found this informative site about traditional salt pans in the Algarve (and west coast of France) - Flor de Sal. Interesting pages include a description of the traditional harvesting process, differences between Flor de Sal, traditional and commercial sea salt, and rock salt (also a good description of all you could want to know about sea salt), and a table giving similar differences between the various salt pan types. Here is some stuff about the history of salt and a pic of salt pans.

And here is a quick overview if you don't want to trawl through those: salt is the next most used raw material after oil; in earlier days it was the cause of wars between nations (consider Gandhi's peaceful demonstration against the British-imposed salt tax) and was so tradeable and highly regarded that some people were paid in salt. The word salary originates from the Latin salarium meaning 'payment in salt'. Traditional harvesting methods date back to at least the Roman Empire and may have been introduced to the Atlantic coast by Phoenicians. By the year 1000 the Portuguese were trading salt over most of western Europe.

Pans, or holes in the ground, hold and allow sea water to evaporate, with the remaining minerals gradually crystallising when certain densities of mineral to water are met. Calcium carbonate is first, followed by sodium chloride (89% of the mineral content in sea salt). Other trace minerals include sulphate, magnesium, bicarbonate and potassium though there is such a long list that you might assume it was contaminated! After a few weeks the pan is dense enough with salt and it is raked out into piles to sun and wind dry.

In commercial panning the evaporation area is larger so by the time the water reaches the crystallisation areas it is already crystallising into sodium chloride and is mechanically harvested before magnesium salts crystallise. Remnant water is then removed and the next sea water received. It is a process to maximise efficient sodium chloride production for industrial purposes. Oh, road de-icing is the world's biggest use of salt.

Rock mining extracts sodium chloride from areas that formed in a way similar to the panning process - this salt originated from sea water too.

Flor de Sal is an intermediate process in traditional harvesting whereby the salt piles are delved through daily by hand to find largish salt crystals forming on the surface. Workers took it for their own home consumption and it is still considered the cream of the crop, having the highest trace element composition.

So now that I'm a bit more informed... I feel even the traditionally harvested salt is far too good to be used for dyeing! It's too healthy by being too mineral laden! But when I see how much they rake up - every few weeks - what I take seems to be so minimal as to be of little consequence. And when I think about the alternatives - commercially driven salt panning or mining - then I come back full circle to traditionally harvested. What I should find out is whether they have a lower grade salt product in the way that Flor de Sal is the highest. And now I know the mineral composition of this sea salt (and of the mini-market salt "salt, anti-caking agents (magnesium carbonate, sodium hexacyanoferrate)"), I can endeavour to find out what happens to them after dyeing and going down the drain. For another day.

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