Harvesting Salt: Solar Pans, Boiling Houses, Bay Water and How a Flake Gets Its Shape
Salt is the only rock we eat, and every grain of it began as dissolved seawater, either the sea outside the window or one that dried up a few hundred million years ago and was buried. Making salt is nothing more than taking the water away. But how the water leaves, fast or slow, by sun or by fire, from the surface or from the bottom, decides what shape the crystal takes, and the shape of the crystal is the difference between a salt that seasons a pot and a salt that goes on top of a tomato. Our finishing salt guide explains what those shapes do on the tongue. This is how they are made.
The chemistry in one paragraph
Seawater is about three and a half percent salt, mostly sodium chloride with smaller amounts of magnesium, calcium and potassium salts. As water evaporates, the brine concentrates, and each salt crystallizes when its own saturation point is reached: calcium carbonate first, then gypsum, then, at around a quarter of the water gone, sodium chloride, and only at the very end the bitter magnesium salts. A skilled salt maker stops before the bitter end. Sodium chloride wants to form a cube, and left alone in still, saturated brine, it does. Every other shape, the flake, the pyramid, the gray grain, comes from interrupting that cube while it grows.
Method one: sun and wind, the solar marsh
The oldest method and still the most beautiful. Seawater is let into a series of shallow clay basins, each one shallower and saltier than the last, and sun and wind do the evaporating over weeks. On the coast of Brittany at Guérande, whose story runs through our Brittany guide, the workers rake the heavy crystals that form on the clay bottom, gray with the clay's minerals, into piles: sel gris, coarse, moist, mineral, the salt for the pot and the pasta water. On calm warm afternoons, a fragile white crust forms on the surface, where evaporation is fastest, and it is skimmed by hand with a flat wooden tool before wind can sink it: fleur de sel, delicate, irregular, faintly sweet, the salt for the plate. Two salts from one pan, decided by where the crystal grew. The same method, in a hotter climate, gives the coarse white sea salts of Sicily, Portugal and Spain, and the pink salt of the Camargue.
Method two: fire, the open pan
Where the sun is unreliable, salt makers boil. Seawater or brine is heated in wide, shallow pans, and the rate of the boil controls the crystal. Boil it hard and you get fine, dense grains, the table salt of centuries past. Hold it at a gentle simmer, just below a boil, and something remarkable happens at the surface: crystals begin at the top, where the brine is most concentrated, and grow downward as hollow, inverted pyramids, held up by surface tension until they are heavy enough to fall. Skimmed at the right moment, they are the pyramid flakes of Maldon in Essex, England, which has made them in open pans since 1882. Jacobsen Salt Co., on Netarts Bay in Oregon, uses a version of the same method: clean bay water filtered and gently evaporated in custom pans until the flakes form and are harvested by hand. Those are the flakes in the truffle salt we stock, and in the plain flake beside it on the salt shelf. A pyramid flake is mostly air and surface; it shatters between the teeth and dissolves fast, which is why it delivers a burst of salt and then vanishes, and why it belongs on top of food rather than in it.
Method three: the mine
Rock salt is a fossil sea, evaporated in a basin that was then buried, and it is mined as solid halite in Poland, Pakistan, Austria, Louisiana and beneath Cheshire in England. Some is quarried and crushed; more is dissolved underground with pumped water and brought up as brine to be boiled into vacuum-evaporated grains, which is where most industrial table salt comes from. Himalayan pink salt is rock salt from the Khewra mine in Pakistan, colored by iron; its flavor is nearly identical to any other salt, and its crystal, ground from a block, is an even cube. Mined salts season food perfectly well. They do not make flakes, because nothing was growing at a surface.
What the method changes
The shape decides the timing. A fine cube dissolves instantly and evenly, which is what a pot of water or a bread dough wants. A coarse gray grain dissolves slowly and unevenly, which is what a roast or a pot of beans wants, and it carries a little moisture and mineral flavor from the clay. A flake or a fleur de sel sits on the surface of food, dissolves in stages as it is chewed, and gives the sensation of salt as an event rather than a background, which is the entire argument for spending on it. The mineral differences between salts are real but small; the texture differences are enormous, and they come entirely from how the water was taken away.
Reading a salt label
"Sea salt" tells you the source and nothing about the method; industrial sea salt from a vacuum evaporator is a fine cube like any other. "Flaky" or "fleur de sel" or "pyramid" tells you a surface harvest. "Sel gris" or "gray" tells you a raked solar marsh. A named place, Guérande, Maldon, Netarts Bay, Trapani, tells you someone stood at a pan. Infused salts, truffle, smoked, herb, are good salts with something added, and the base flake still matters; our truffle guide explains why a flake carries an infusion better than a grain.
Salt in the pantry
Three salts cover every job. A fine or kosher salt for cooking, seasoning and dough. A coarse gray sea salt for pots, roasts and pasta water. A flake for the table, the plate and the last second. The flakes and the gray are at 263 Josephine Street in Cherry Creek, Denver, and ship nationwide from theambrosianpantry.com. Keep the flake in a dry jar with a wide mouth, take a pinch with your fingers rather than a spoon, and use it on the tomato, the chocolate and the caramel, where a crystal that took a week of sun to grow can be tasted for what it is.
