Almost 2,000 years ago, the Roman naturalist and philosopher Pliny the Elder said, “Heaven knows, a civilized life is impossible without salt,” and it’s safe to say nothing has changed. Across the world, salt is prized for the way it makes food of any kind taste better, no matter if it’s simple buttered noodles, a slab of watermelon, or expensive beef tartare.
Salt is a flavor “potentiator”; it doesn’t add flavor of its own so much as bring out the desirable flavors in other foods. It makes rich foods taste richer and meaty foods meatier, and it also has the ability to ameliorate bitter flavors.
Of course, humans crave salt in part because we need an element contained within it to survive. Salt is, chemically speaking, an ionic compound made up of sodium and chlorine. Our bodies need sodium in order to regulate and balance fluid levels in our blood and around our cells, and it plays a key role in nerve and muscle functions.
How Salt Is Processed
Salt is everywhere, and is one of the world’s oldest commodities. It can come from seashores, where ocean water is harvested and allowed to evaporate, leaving salt behind. But it can also come from inland saltwater springs; from ancient caves that were once part of or connected to the ocean; and, in even rarer instances, from the shores of landlocked lakes that are all that remains of ancient oceans that once covered the land around them.
Today, much of the world’s salt comes from salt mines, which use the same “room and pillar” technique traditionally employed in coal mines. Drills bore holes into the earth, and explosives are placed in the holes and detonated, creating new rooms to excavate. When the mines are dug out, sturdy pillars are left in place to hold up the ceiling. This means not all of the salt is harvested, as some has to stay behind to ensure the mines don’t collapse.
The most famous salt mine is the Khewra Salt Mine in Pakistan, where all Himalayan pink salt is produced. The huge mine doubles as a tourist attraction; parts of the mine are so spacious that they resemble cathedrals, and it is large enough to hold a food court and a mosque—all, appropriately, made out of salt. Much of the work done by machinery in other salt mines is done by hand in the Khewra mine, with hand-cranked drills and men manually laboring to excavate the caves. The pink-salt cave runs for miles underground in the roots of the Himalayas.
Kinds of Salt
While there are many categories of salt, it’s important to remember that all edible salt, no matter the color, moisture content, or crystal size, is sodium chloride, and all salt originates from the oceans and seas, even if it isn't harvested directly from the water. The differences in types of salt come from variation in production methods and trace amounts of minerals, sulfates, soil sediments, algae, and bacteria. Sometimes dyes and flavors are added after harvesting to produce a colored or flavored salt—really, a seasoning, passed off as a salt.
Salt can’t be "organic," as food and spices can, because it’s a mineral and therefore isn’t organic material. (It may sometimes be labeled “organic” to indicate that it doesn’t contain anti-caking agents, but the term in its true meaning doesn’t apply.) In a similar, often misleading vein, a lot of marketing copy attempts to heighten the allure of small-batch, rare, expensive salts, but what you’re getting is still sodium chloride, despite any additions or exciting ads.
There are very subtle flavor differences between, say, French gray sea salt and Himalayan pink salt, and they stem from the very small percentage of salt's makeup (roughly 5%, generally speaking) that is not sodium chloride. While some people claim they can taste the differences between salts, most people can’t. (Max Falkowitz disputes this idea somewhat in a 2011 article written for this site on tasting specialty sea salts.)
If your tongue senses a difference between salts, it’s likely picking up on attributes other than flavor—texture, surface area, crystal structure—all of which are directly related to the way a given salt is produced, not its origin.
Because salt crystals can take on any number of shapes, the density of different salts can vary wildly. A tablespoon of table salt is more dense than a tablespoon of kosher salt. Crystals of table salt, small and uniform, will stack together in a tight formation, with very little air in between. The shape of kosher salt, on the other hand, makes the crystals stack more like packing peanuts: The salt crystals don’t rest side by side, and there are larger gaps between them, which means the same mass of salt will occupy a greater volume.
The names we give to salt don’t usually adhere to a set of standards, but instead reflect how we use them. Table salts vary by brand, as do kosher salts—some have iodine, some have anti-caking agents, some have neither. “Rock salt” can be the salt that you put into salt grinders, or the stuff poured on icy roads in the winter. "Sea salt," especially, is a name that refers to the harvesting method and nothing else—in fact, the culinary cachet attached to “sea salt” has led to instances of mined salt carrying the label, as the term is not regulated. (And, of course, it’s technically true.)
Using satellite view on Google Maps, you can see the salt flats operating in Guérande, France, much as they have for hundreds of years. Streams of water from the ocean are channeled into rectangular pools, and a sluice system moves the salty water from one pool to the next; the water is allowed to evaporate, and the saline level increases.
The traditional French method for drying salt produces two kinds of salt: sel gris, or gray sea salt, and fleur de sel. Gray sea salt is raked up from the depths of ponds known as oeillets, and it takes on its characteristic hue via contact with the gray clay that lines the bottom of the ponds.
Unlike other sea-salt producers elsewhere, the French choose not to dry their salt completely; as a result, according to Mark Bitterman’s book Salted: A Manifesto on the World's Most Essential Mineral, With Recipes, French gray sea salt has a moisture content of about 13%, giving it an almost soft consistency. Gray sea salt clusters in chunks, making it a finishing salt that’s both attractive and practical, as its relatively wide crystals spread easily over surfaces.
Fleur de sel (literally "flower of salt") is produced using the same French-seaside sluicing system, but instead of being raked up from the bottom of the oeillets, it is harvested from the water’s surface. At a certain point during the evaporation process, the salt becomes so concentrated that it forms fluffy crystals that float on top of the water. After those crystals are harvested and dried, the salt is gray and moist, just like sel gris, but the larger crystals have a pronounced crunch.
Hawaiian salt is like any other sea salt, harvested from the ocean, but the last rounds of drying are completed in beds dug into lava. The lava can be brick-red to black in color, so you’ll see both “red Hawaiian salt” and “black Hawaiian salt” on the market. These can also be called “volcanic” or “clay” salt.
Adding charcoal can turn salt black in a way that's reminiscent of salt dried in black lava beds, so a lot of cheaper “black salt” is regular old sea salt with added activated charcoal. Sometimes “black salt” looks dark brown and black because other spices have been added or cooked with the salt to turn it a darker shade.
Unlike French sea salts, Hawaiian salt is not moist but totally dried. There’s no real regulation of these salts, so use your judgment and discretion when buying colored salts. Don’t assume that a salt billing itself as "Hawaiian" has been dried using the traditional lava-bed methods.
There's no regulation of the term "table salt" either, but table salt is what most people think of when they hear the word "salt": the small, cubic, uniform crystals found in saltshakers. Because of its grain size, table salt doesn’t do as good a job of covering the surface area of foods as other, crunchier salts, but the small shape of the crystals helps the salt flow easily.
Some table salt comes from salt works on ocean shores, where the brine is brought indoors and evaporated in large metal pans. Some table salt is mined and added to water to create a solution, which is then evaporated to form the characteristic crystals of table salt. Still other producers use a sifting method, simply breaking down large pieces of salt and using a series of mesh screens of different sizes to separate out the table-salt size we’re familiar with.
Some, but not all, table-salt makers add an anti-caking agent so the salt doesn’t clump. This additive is typically silicon dioxide, also known as silica, a naturally occurring compound that absorbs moisture to stop the salt crystals from sticking together, keeping the salt itself dry and free-flowing. Other anti-caking agents, like tricalcium phosphate and dextrose, are similarly used in tiny amounts and are safe to consume.
Regardless of the compound, anti-caking agents make up 2% or less of the material in salt, and will be listed among the ingredients. If the only ingredient listed is salt, there are no anti-caking agents present.
Likewise, some (but not all) table salts contain iodine, a nutrient that naturally occurs in salt but is removed during the cleaning and drying process. The elimination of iodine can cause real problems, as iodine deficiency can lead to thyroid dysfunction in adults and intellectual disabilities in infants and children whose mothers were iodine-deficient during pregnancy.
Since the 1920s, the US has added iodine back to table salt. Today, iodine deficiency is less of a problem than it was in the past, but some still suffer from a lack of iodine in the diet. If your table salt doesn’t contain iodine, the label should read something like “This salt does not contain iodine, a necessary nutrient.”
Kosher salt, on the other hand, loses its iodine during the drying process and does not have it added back. The other main difference between table and kosher salt is the shape and size of the crystals; table salt is like icy hail compared with the larger, fluffier snowflakes of kosher salt.
While the smaller crystals of table salt tend to bounce off foods and settle into cracks, kosher salt melts on contact with many foods, causing the crystals to stick. This consequently means it covers the surface of foods more evenly. Professional cooks tend to prize kosher salt’s thicker, coarser texture, which makes it easier to pinch and sprinkle over food. It’s an excellent all-purpose salt.
"Kosher salt" is so named because it was traditionally used by butchers to ritually cleanse meat and make it kosher, in accordance with Jewish dietary laws. Koshering, or "kashering," in addition to rinsing and removing blood from meat, includes a step in which the meat is covered with a fine layer of salt. Because the larger crystals of salt more easily covered the surface of the meat and absorbed more liquid, salt with a larger grain size became known as "kosher salt."
There isn’t a single, standard practice for producing kosher salt, which becomes evident when you closely compare Morton kosher salt and Diamond Crystal kosher salt, since they have different densities. This difference doesn’t matter if you’re using kosher salt to sprinkle on top of food, but it can come into play in baking (and other) recipes if you use volume to measure out salt instead of mass.
Morton kosher salt also contains the anti-caking agent yellow prussiate of soda, or sodium ferrocyanide, while Diamond Crystal does not. For more on kosher salt (plus a chart detailing the various densities of common salts), see Kenji's 2013 article on why kosher salt is better in many cooking applications.
Himalayan Pink Salt
All Himalayan pink salt, as mentioned earlier, is excavated from a single mine in Pakistan. The color comes from trace elements, some of which are more concentrated in certain parts of the mine. These differences give the salt a range of hues, from pale pink to a deeper, almost beet-pink color.
It is perhaps because of its origins that some Westerners, quick to exotify Eastern places like Pakistan and eager for untapped sources of health benefits, have assigned near-mystical powers to Himalayan pink salt. From pink-salt lamps to salt-infused spa rooms, there’s no salt so fetishized for reasons beyond its use in food than the pink kind from the Himalayan foothills. Apart from its aesthetic value, some claim that Himalayan pink salt is healthier to consume. It’s important to remember that there is no scientific research to back up any of these health claims.
While it may not be a panacea, Himalayan pink salt is one of the very few colored salts that gain their colors naturally, and it’s beautiful—it practically glows.
Himalayan pink salt can be as fine as table salt, or it can come in chunks big enough to put in a salt grinder. Or it can be bigger still, in slabs as large as plates and an inch thick, which can be used to cook on. The food may absorb a bit of the salt that's on the surface of these slabs, but the practice of using them to heat food is more to put on a show than to affect the food itself.
"Flake salt" can mean a couple of different things, though, in general, it refers to salt crystals with a large surface area. Sometimes people refer to Morton kosher salt as flake salt because of its flatness. The best-known "flake salt" is the kind from Maldon in England, probably because the salt is branded as “sea salt flakes.” But this distinct salt is not flat: It has a pyramidal shape that’s brittle and crunchy, making it an excellent finishing salt.
"Slab salt" is the name given to those plate-like slabs of Himalayan pink salt that food is cooked on; in some restaurants, they're used to serve food. A slab of salt retains heat well, so it can stay hot or cold for a long time. While the term “slab salt” could be applied to any tray-like piece of salt, it usually refers to mined slabs of Himalayan pink salt.
The term “rock salt” simply refers to large chunks of salt, and it can apply to large-sized salt produced for both culinary and nonculinary uses. For example, it can be used to display food, as with Oysters Rockefeller; in ice-cream making; and in baths. While rock salt made for nonculinary uses may be safe to consume, it will not have gone through the cleaning processes culinary salt undergoes, which get rid of elements that may be unpleasantly bitter, like calcium.
This term also refers to the larger chunks of salt you sometimes find in salt mills. Keep in mind that, unlike pepper, which is ground to release its inner volatile oils and flavor, all that happens to salt in a grinder is that the pieces are made smaller.
“Rock salt” can also mean the salt used to melt ice on roads—definitely not the kind you want mixing in your food.
Pickling salt, used in pickling and canning, is a very fine-grained salt with no anti-caking agents or iodine, which will make a brine cloudy. The small size of the grain allows pickling salt to dissolve quickly into the brine.
Other salts can be substituted if they're likewise free of anti-caking agents and iodine; Diamond Crystal kosher salt makes a good pickling salt, while Morton kosher salt, as already mentioned, contains an anti-caking agent and therefore shouldn't be used in pickling. (And keep in mind that salt sold as "pickling salt" will be much finer than kosher salt, so you'll have to make up for the difference in volume by adding more kosher salt than you would pickling salt.)
Kala namak, also known as “Himalayan black salt,” has an unmistakable and unique flavor. This mined salt from India is cooked in a kiln, a process that changes the small amounts of trace elements into more noticeable sulfurous compounds, which makes the salt taste a little like overcooked boiled eggs (some have described the flavor as similar to rotten eggs). But the sulfurous flavor is muted somewhat when used in dishes, and it appears frequently in the many cuisines native to the Indian subcontinent, in spice mixes like chaat masala and in condiments like raita.
Kala namak comes both in large chunks, which vary in color from copper to deep caramel to black, and in ground form, which varies in color from a lighter purple to a soft red.
Infused and Seasoned Salts
Like kala namak, other salts are prepared or cooked to add flavors. Smoked salts are like smoked meats: They absorb the flavor of what they’re smoked with, just as a steak can taste different when smoked over charcoal versus treated wood. Often, smoked salts include other spices, and some smoked salts are just salt coated in liquid smoke oil.
Seasoned salts (like the most famous seasoned salt of all, Lawry’s) are spice mixes that contain added sugar and salt.
Many infused, flavored, and colored salts on the market are the result of simply adding food dye or flavorings to the salt, so a little skepticism on the part of the consumer is necessary. Bacon-infused salt sounds good, but when would you actually use it? Salts can be infused with aromatic ingredients, like saffron, garlic, vanilla, and herbs; with condiments, like sriracha; or even with truffles. Because salt is a preservative, it’s easy to infuse flavors into salts—you can even do it at home. (Learn more in Max's article on how to use flavored salts.)
How to Use Different Salts
There are no rules for how to use salt. You may find you enjoy a red Hawaiian salt on guacamole, but stick with a large-flake salt on bread and butter. Personally, I use kosher salt nine times out of 10, and save the colored, infused, and large-flake salts to use as fun finishing salts at the table, adding color and texture to the surface of foods. Play around with different kinds of salts, and you’ll quickly discover what's worth the expense and when a cheaper option is just as good.
*Editor's Note: A previous version of this article contained the assertion that charcoal and lava had similar chemical composition; we regret the error.