Here's How We Get Culinary Salt and 6 Kinds to Cook With

The author of a historical manifesto called "Salted" answers our essential questions about the mineral — from how salt is made to which one's the best for popcorn.

When a question comes up about salt — and there are so many — some of the country's best chefs and food artisans turn to one man: Mark Bitterman.

What is salt?

Chemists would say it's sodium chloride, but why does it come in so many shapes and sizes? Mark Bitterman's salt fixation began in France more than 25 years ago, when he met Michelin-starred chefs who traveled with their own precious supply. Along with his wife, Jennifer, Bitterman now owns a store called The Meadow, with branches in Portland, Oregon, and New York City, that sell salts from all over the world. Many are tracked down by Bitterman or custom-made, like his house fleur de sel.

Related: Why Chefs Love This 600-Million-Year-Old Salt From West Virginia

How is salt made?

Historically salt is made in one of three ways: solar evaporation, fire evaporation, or mining.

Solar salt is made by bringing sea water in from the ocean and passing it through a series of ponds. As it goes from one pond to the next, the sun and wind evaporate out the water, leaving behind a concentrated brine that begins to crystallize. Solar salts include fleur de sel and sel gris. Solar evaporation is the old-school way almost all salt in the world came to us. Now there are huge industrial solar-evaporated salt farms — Cargill has the biggest sea salt farm in the U.S., in the San Francisco Bay. So just because someone called it sea salt doesn't mean that it's something beautiful made by handsome blue-eyed men with rakes on the side of the ocean — it can also be harvested by bulldozers.

Fire-evaporated salt is made by boiling the water out of a brine solution to form salt crystals. This can be done in a low-tech, artisan way over open vats, as with flaky salts, or it can be done in a mechanistic, mass-production way using vacuum evaporators. (Vacuum evaporators are more fuel-efficient, because water boils faster at lower atmospheric pressure.) A couple of artisan salt producers like Quoddy Mist in Maine make a hybrid salt by pre-evaporating a brine in vacuum evaporators, then crystallizing it in open pans.

Mined salt is dug out of an ancient salt deposit that was an ocean several hundred million years ago. Most mined salts are used for roads and other big industrial applications. A small amount is used for culinary purposes, like the Himalayan salts harvested south of the Himalayas in Pakistan and the mined salts in Bolivia. They're considered purer because their deposits predate pollution and also healthier because of their mineral content. But most good sea salt is virtually as pure as good mined or rock salt, and many have just as high or higher mineral content. So Himalayan salt is healthy, but so are lots of other salts. Many traditional salts, below, are mined.

What are the different kinds of salt?

Artisan salts fall into roughly six categories: fleur de sel, sel gris, flake salts, traditional, rock, and shio salts. Industrial salts have their own category, as do flavored salts like smoked salt. The three foundation salts for American cooking — and the ones I encourage people to stock at least one of in their pantry — are fleur de sel, sel gris, and flake salt.

Fleur de sel is a solar-evaporated salt raked off the top of a salt pond. Delicate, irregularly shaped, each crystal has the complexity of a snowflake, as well as a lot of residual moisture and minerals. That moisture means the salt won't dissolve right away, but glitters on the surface of any food. When the crystals hit your mouth, the smaller ones dissolve first, then the larger ones, to give this modulated sensation that's much more sparkly and dynamic than shaker salt, where every crystal is identical. It's a beautiful all-purpose finishing salt, great on fish, cooked vegetable dishes, scrambled eggs, pork — any food that's medium-bodied and not too intense. I especially love it on toast and butter, to show you how hoity-toity my tastes are.

Sel gris has these huge, chunky crystals that have a ton of minerals and a ton of moisture. Sel gris is naturally coarse, and naturally found that way. You rake it off the bottom of a salt pond every day or two. You don't want to put this on something delicate. So you can put it on something huge and hearty — a big, juicy steak, a big piece of prime rib. It appears to deliver the salt differently. It takes longer to dissolve, it penetrates through the food at a different rate and it gives you better results. It's great for steak, lamb, root vegetables, roasts. And if its ground more finely, it can be a great all-purpose cooking salt.

Related: A Bottle of Salt Spray Changed How I Cook

Flake salts come from all over the world — Maldon is your very middle-of-the road flake, and there are delicate, fine ones like Marlborough Flaky, and massive ones like our house, Meadow flake. A flake salt is basically a parchment–fine crystal with no moisture, or very little, and little minerals. It does the opposite of a fleur de sel or sel gris. Instead of judiciously dissolving in your mouth along with every bite, it goes pop! It sparkles. It gives you this incredible electrostatic crackle of salt that illuminates everything and then disappears. Because of the way they flash then fade to let the food shine through, I like flaky salts in lighter foods: salads, steamed vegetables, grilled salmon, baked goods like dinner rolls or pretzels, even chocolate chip cookies. Flake salts can also be good on Caprese salads, but that's a war, because flake salts are great on tomatoes, but fleur de sel is wonderful on mozzarella. So you have to pick your battles.

Traditional salts are made the most old-fashioned way: Take a bunch of sea water, bring it into a basin, let it evaporate until there's nothing left but a foot or three of salt, scrape it all up, grind it down and sell it. Traditional salts make up the bulk of all sea salts. They're probably the most varied category because so many different people make them. There's the simple white Trapani salt from Italy with only 3% mineral content, all the way to the vibrant Hawaiian red salts with closer to 15 percent minerals. They also range from very fine to chunky. They're historically made in countries where the weather is constant — Sicily, Tunisia, Spain, Portugal, Ghana, Tanzania, Brazil, Argentina — all these places with phenomenal climates, where salt makers don't have to worry about rain like they do in France.

Rock salts are mined salts. They're often very pretty. And people like them because they're pure and unrefined, though sea salts are often just as pure. Rock salts work wonderfully if you're making a drink or boiling pasta water, anywhere they get dissolved. But to sprinkle them on top of something, they have to be very finely ground before they cease to present a chunky obstacle to your teeth.

Shio salts are all but unknown in America, but shio means "salt" in Japanese. These are simmered over a cauldron until they form these superfine crystals. They're often made with deep ocean water, because the Japanese recognize the oceans have different bands of minerals at different depths. The water is also purer because there's less pollution down there. To form the crystals, the salt makers put the ocean water over a wood fire and stir it with a paddle. This frustrates the crystallization, forcing the sodium chloride to take up more of the minerals. Shio salts often feel like snow on the palate. They're great in a delicate sauce or broth, and on steamed vegetables, though their grains are so fine they're better tossed with the vegetables than sprinkled onto them, to avoid clumping.

How is industrial salt made?

Salt manufacturing has changed dramatically in just the last 150 years. Humans have been eating salt for a couple of hundred thousand years; for millennia salt has been this natural, hugely complex ingredient with 84 minerals, residual moisture and irregular, complex crystals. It was only 150 years ago, with the advent of the modern chemical industry, that we invented table salt. Made by injecting water into a salt deposit underground to form a brine, that brine has what salt normally has — trace amounts of magnesium, potassium, and other minerals. But it is refined through added chemicals to form pure 99.99% sodium chloride crystals. Most of this refined salt is manufactured for huge industrial applications. But they also package some of it up in a box and call it food for human beings. To talk about that as a norm, as the definition of salt — even as a food to be eaten — is unbelievable.

"My go-to chocolate chip cookie salt is Bali Rama flake salt. I think it means 'Balinese daddy salt,'" says Bitterman. "It looks like hollow, arrowhead-shaped pyramids, which provide a really wild, pop-rocks, explosive crunch."

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