Walk into any professional kitchen, and you’ll see big, open boxes of Diamond Crystal or Morton. It’s always kosher salt. You won't see that little blue cylindrical canister with the girl in the yellow raincoat unless the chef is cleaning a cast-iron skillet or something. Why? Because the difference between kosher salt and iodized salt isn't just about some "fancy" branding or a higher price tag. It’s actually about how you taste food, how you control seasoning, and whether or not your dinner ends up tasting like a swimming pool.
Most of us grew up with that fine-grain table salt. It was cheap. It was everywhere. But if you’ve ever followed a recipe and found the dish was way too salty—or strangely bitter—you probably fell victim to the density gap.
Why the Difference Between Kosher Salt and Iodized Salt Actually Matters
The biggest thing to understand right out of the gate is volume. This is where people mess up. Iodized salt is dense. It’s made of tiny, uniform cubes that pack together tightly in a spoon. Kosher salt is flaky, hollow, and jagged. If you take a tablespoon of iodized salt and a tablespoon of kosher salt, you aren't holding the same amount of salt.
You're holding about twice as much "saltiness" in the iodized spoon.
Iodized salt usually contains about 2,300 milligrams of sodium per teaspoon. Diamond Crystal Kosher salt? It’s closer to 480 milligrams per teaspoon. That is a massive discrepancy. If you swap them one-for-one, you're basically nuking your palate. This is why professional chefs like Samin Nosrat, author of Salt, Fat, Acid, Heat, swear by kosher salt. It’s harder to over-salt things because the grains are physically larger and less dense. You can see them. You can feel them between your fingers. It gives you a sense of control that a fine-grain shaker simply can't provide.
The "Iodine" in Iodized Salt
Then there’s the chemical side. Iodized salt is a relatively modern invention. Back in the 1920s, the US government noticed a lot of people in the Great Lakes and Pacific Northwest regions were developing goiters—swollen thyroid glands—because of iodine deficiency. They decided to spray potassium iodide onto table salt. It worked. It was one of the most successful public health initiatives in history.
But there’s a trade-off.
Iodine has a metallic, slightly medicinal aftertaste. Honestly, once you start noticing it, you can't stop. If you’re boiling a giant pot of pasta water, maybe it doesn’t matter. But if you’re seasoning a delicate piece of white fish or a summer tomato, that chemical twang is going to show up. Kosher salt, by definition, is pure sodium chloride. No iodine. No "medicine" flavor.
The Texture Factor: Flakes vs. Cubes
Let's talk about the "kosher" name for a second. It’s a bit of a misnomer. The salt itself isn't "more kosher" than other salts in a religious sense. All pure salt is kosher. It’s actually called koshering salt because its large, jagged flakes are ideal for the process of koshering meat—drawing out blood.
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The surface area is the key.
Because kosher salt crystals are flat or hollow, they stick to food better. Think about a steak. If you sprinkle fine table salt on a raw ribeye, it mostly just dissolves into a brine immediately or bounces off. But kosher salt? Those big flakes grab onto the muscle fibers. They create a crust.
Morton vs. Diamond Crystal
Even within the world of kosher salt, there is drama. This is a hill many chefs will die on. Morton Kosher Salt is made by rolling salt crystals between high-pressure rollers. This makes them hard, dense flakes. Diamond Crystal, on the other hand, is made using the Alberger process—a method of evaporation that creates hollow, pyramid-shaped crystals.
Diamond Crystal is even less salty by volume than Morton. Most high-end recipe developers (think Bon Appétit or NYT Cooking) use Diamond Crystal. If you use Morton and the recipe calls for Diamond, your food will be about 20% saltier than intended. It’s a mess.
When You Should Actually Use Iodized Salt
It isn't all bad news for the blue box. Iodized salt has its place. Because it’s so fine, it dissolves instantly. This makes it the better choice for baking. If you’re making a cake batter or a cookie dough, you want the salt to distribute evenly throughout the fat and flour. Using big chunky kosher flakes can lead to "salt pockets," which are fine on top of a chocolate chip cookie but weird inside a sponge cake.
Also, if you live in an area where your diet is naturally low in iodine—meaning you don't eat much seafood or dairy—iodized salt is still a legitimate health tool. The World Health Organization still pushes for universal salt iodization in developing nations to prevent cognitive disabilities in children. It’s important stuff.
But for the love of everything, don't use it to season your soup at the end of cooking.
Solubility and Brining
If you’re making a brine for a Thanksgiving turkey, the difference between kosher salt and iodized salt becomes a math problem. If the recipe says "1 cup of salt" and doesn't specify which type, you are playing a dangerous game. 1 cup of iodized salt weighs roughly 300 grams. 1 cup of Diamond Crystal kosher salt weighs about 140 grams.
You could literally double the salt content of your bird by using the wrong box.
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If you're stuck with iodized salt but want to follow a "kosher salt" recipe, the rule of thumb is to use half as much. Use your eyes. Use your tongue. Taste as you go.
Additives and "Anti-Caking" Agents
Iodized salt almost always contains anti-caking agents like calcium silicate. This is what keeps the salt flowing smoothly out of a shaker even when it's humid. Without it, salt clumps together into a brick.
Kosher salt (specifically Diamond Crystal) often has no additives at all. Morton adds yellow prussiate of soda as an anti-caking agent, but it’s still much "cleaner" than table salt. Why does this matter? For fermentation. If you’re making sauerkraut or pickles, the additives in iodized salt can turn your brine cloudy or even inhibit the "good" bacteria you’re trying to grow. Real fermenters won't touch iodized salt with a ten-foot pole.
Actionable Insights for Your Kitchen
Stop treating salt as a single ingredient. It’s a tool. To master the difference between kosher salt and iodized salt, change how you shop and cook with these steps:
- Buy a Salt Cellar: Throw away the shaker. Put your kosher salt in a wide-mouthed bowl or "salt pig." Use your fingers to season. This is the only way to truly learn how much salt you're adding.
- Pick a Brand and Stick to It: Whether you choose Morton or Diamond Crystal, stay loyal. You need to "calibrate" your hands to the weight and feel of that specific grain. If you jump back and forth, your seasoning will be inconsistent.
- Save Iodized for the "Invisible" Tasks: Use it for salting a giant pot of potato water or for baking recipes that call for "table salt." It's cheap, so use it where the nuance doesn't matter.
- Check the Label for Fermentation: If you're pickling, look for "Pickling Salt" or pure Kosher salt with zero additives.
- Scale by Weight, Not Volume: If you want to be a pro, stop using teaspoons. Use a kitchen scale. 10 grams of salt is 10 grams of salt, regardless of whether it’s flaky, fine, or pink.
Understanding this distinction is the fastest way to level up your cooking. It’s not about being a snob; it’s about the physics of the crystal and the chemistry of the iodine. Once you make the switch to kosher salt for your daily seasoning, you'll notice your food tastes more like itself and less like "salt."