Kosher Salt

Chemically, all salt is sodium chloride (NaCl). Both table and kosher salt can be harvested from either seawater or underground salt beds; Diamond Crystal and Morton both harvest their salt from underground. According to representatives from both brands, the first step in their respective salt-making processes is pumping water into the salt beds to form a brine, which is then forced to ground level. The companies evaporate the brines using strictly controlled methods that determine the size, shape, and density of the salt crystals.

According to Erica Williams, a senior manager on the consumer insights team at Morton, Morton's brine is pumped into huge commercial vacuum evaporators that are about three stories high. As the pressure in the vacuum decreases, the brine boils at progressively lower temperatures, saving both time and energy. To give Morton kosher salt its distinctive size and shape, Williams said, the remaining salt particles “are pressed through high-pressure rollers and flattened into large, thin flakes.” Finally, the flakes are run through screens to ensure a uniform shape.

The process used to make Diamond Crystal salt differs from Morton’s process in a few important ways. Diamond Crystal is the only company in the United States to use the Alberger process, a technique developed in the 1880s that heats and agitates the extracted brine in a series of open containers. The combination of slow heating and agitation causes hollow kosher salt crystals to form on the surface of the brine. (For more information, see this graphic from Cargill, which owns Diamond Crystal.) As larger crystals form, smaller crystals also form and stick to the larger crystals, resulting in a mix of shapes and sizes. Unlike the grains of Morton kosher salt, the larger grains of Diamond Crystal kosher salt are not flattened or flaked before packaging.

Recipes commonly call for salt by a measure of volume (e.g., 1 teaspoon). However, 1 teaspoon of table salt, Morton kosher salt, and Diamond Crystal kosher salt will not deliver equal amounts of saltiness. The tiny grains of table salt fit tightly together in a teaspoon measure, weighing about 6 grams regardless of the brand. Of the two major brands of kosher salt, Morton grains are considerably heavier, denser, and more uniform in shape and size than the hollow, pyramidal Diamond Crystal grains. One teaspoon of Morton kosher salt weighs 4.8 grams, while one teaspoon of Diamond Crystal kosher salt is the lightest of the three, weighing just 2.8 grams. In other words, a volume measurement of table salt will contain about twice as much salt as an equal volume of Diamond Crystal kosher salt, and Morton is roughly in the middle of this range.

Diamond Crystal has long been the test kitchen’s go-to kosher salt. We love it for the same reason it’s the preferred kosher salt of many food professionals: Diamond Crystal’s soft, hollow crystals are easy to crush and sprinkle by hand. But since we also routinely call for measuring salt by volume when making a brine or a salt rub, we wondered if Diamond Crystal kosher salt is really the better choice. To find out, we set up a series of tests.

First, we conducted two blind tastings of the two kosher salts: plain and sprinkled on buttered bread. In both instances, tasters preferred the “delicate and fleeting crunch” of Diamond Crystal. It adhered well to the butter, crunching slightly before dissolving and disappearing “like a snowflake on your tongue.” This trait has practical implications for cooking. As cook and author Samin Nosrat points out in Salt, Fat, Acid, Heat (2017), “the more quickly salt dissolves, the less likely you are to overseason a dish, thinking it needs more salt when actually the salt just needs more time to dissolve.” In comparison, the Morton grains were noticeably bigger, crunchier, and harder. When seasoning food with kosher salt, we like to gently squeeze it between our fingers because it breaks up the largest crystals and gives us a clear sense of how much salt we’re adding. When our tasters sprinkled Morton kosher salt onto buttered bread slices, it didn’t crush between their fingers quite as easily and didn’t disperse as evenly. We still liked its flavor and crunch, but not quite as much as we liked bread samples sprinkled with Diamond Crystal. 

In our second test, we set out to see if we could detect the same level of saltiness in two batches of chicken broth: one seasoned with 1 teaspoon of Morton and one seasoned with 1½ teaspoons of Diamond Crystal (identical amounts of the two salts by weight). Both salts dissolved well in the warm liquids, so there were no textural differences between the two broths, which tasted exactly the same.  

Although Diamond Crystal is still our preferred kosher salt, Morton kosher salt will also give you excellent results in the kitchen. Table salt will, too. However, because different styles and brands of salt are wildly different in density and size, you should always pay close attention when substituting one for another. You can also follow a simple conversion: 1 part table salt = 1½ parts Morton kosher salt = 2 parts Diamond Crystal kosher salt. Put another way, if you’re making our Perfect Chocolate Chip Cookies, you could use the 1 teaspoon of table salt called for in the recipe or swap it out for 1½ teaspoons of Morton kosher salt or 2 teaspoons of Diamond Crystal kosher salt. Fortunately, it’s becoming increasingly common for food magazines and cookbooks to indicate which type and brand of salt was used when developing recipes. 

We’re huge fans of kosher salt, no matter the brand. Unlike the tiny grains of table salt, the coarse grains of kosher salt are easy to pick up with your fingers and are especially well suited for rubbing into meat or sprinkling over food when seasoning to taste. Diamond Crystal kosher salt has been and will continue to be the test kitchen’s go-to kosher salt. The company’s patented processing method results in delicate, hollow crystals that are easy to pinch and distribute evenly. We also love that its grains adhere well to foods—from steak or broiled vegetables to a simple slice of buttered bread—and dissolve quickly.