"More and more I see recipes specifying kosher(ing) salt or sea salt in recipes. I'm all for using gourmet ingredients but Serious Eats even proposes using sea salt to preserve Meyer lemons! Does there remain any use for which the much more affordable regular American-style iodized salt is preferred, or should I just use what I have left and only stock the higher-end stuff?"
First of all, let's get one thing straight: Chemically, there is virtually no difference between table salt, kosher salt, and fancy sea salt. All of them are close to 100% pure NaCl (sodium chloride), with a few trace elements thrown in. In the case of table salt, those ingredients are there to prevent it from caking (hence the old "When it rains, it pours" Morton's slogan), while with sea salt, they come along for the ride when the salt is harvested from the ocean.
Dissolve those salts in water side by side, and the differences between them become nearly indistinguishable, just as they are when you use them to season your food.
There are, however, a few key distinctions that will affect how you use them.
Relative Bulk Density of Salts
First off is bulk density, or the amount of mass within a given volume of a granular solid. Regular table salt is comprised of many minute, regularly shaped cubes. This allows the granules to pack together tightly in a given space. Kosher salt, on the other hand, forms large, craggy flakes that don't fit together very well. Put them into a container, and you also end up with plenty of air space. What does this mean for cooking? It means that if you are measuring by volume, different types of salt are not interchangeable. A cup of table salt will have twice the salting power of a cup of Diamond Crystal kosher salt.
Here are the relative densities of a few common types of salt you'll find:
Salt Mass and Volume
|Type of Salt||Weight per Cup||Weight per Tablespoon|
|Table Salt||10 ounces; 280g||2/3 ounce; 18g|
|Morton's kosher salt||8 ounces; 225g||1/2 ounce; 14g|
|Diamond Crystal kosher salt||5 ounces; 140g||1/3 ounce; 9g|
|Maldon sea salt||4 ounces; 115g||1/4 ounce; 7g|
|Fleur de sel||8 ounces; 225g||1/2 ounce; 14g|
Thus, if a recipe calls for Diamond Crystal kosher (as most of our recipes do) and all you've got is table salt on hand, you'll have to halve the amount by volume to get similar results.
All salt is technically kosher. "Kosher salt" is really a misnomer for koshering salt, as its large grains make it more effective at drawing out liquid from meat during the koshering process. But that's not why chefs like to use it.
The biggest reason why chefs love to use kosher salt is that it is much easier to pick up between your fingers, and thus gives you tighter control over your seasoning. Think about this: How many times have you gone to a restaurant, reached for the saltshaker, shaken it over your food, and realized that almost no salt was coming out? And how about the opposite? How many times have you accidentally oversalted your food while trying to use table salt from a shaker?
Even trying to apply table salt by hand is a tricky feat. Its small, smooth grains slip past each other, sliding through your fingers like sand through an hourglass. This lack of control is frustrating in the kitchen.
Kosher salt, by contrast, has larger, coarser grains that are easy to feel and easy to sprinkle, making it much easier to gauge the proper level of seasoning. You can pick up a big pinch of kosher salt and hold it between your fingers without accidentally dropping grains, until you are ready to start sprinkling.
Distributing seasoning evenly is also easier with kosher salt. Try this quick experiment: Grab a sheet of black cloth, a bowl of kosher salt, and a bowl of table salt. Now lift up some table salt between your fingers and sprinkle it on the cloth, doing your best to cover a two- by two-inch square area evenly. Repeat with the kosher salt. Which one distributed more evenly?
Yep, I thought so.
When Is Table Salt Okay?
All that said, there are occasions when it's totally fine to use table salt. So long as your salt is going to be dissolved and distributed evenly in the final dish—as with a soup, stew, or braise—there's no reason to use kosher salt other than the convenience of not having to buy two separate types of salt. Just remember to check your recipes, and make sure to compensate for table salt's density when adding it.
There is one occasion when table salt actually has a small leg up over kosher salt: when you need to dissolve it quickly in a liquid. When you're making a high-salinity solution (such as a brine), table salt will dissolve a little faster than kosher salt due to the smaller size of its crystals. Incidentally, did you know that maximum solubility of salt in water is pretty much the same no matter how hot or cold your liquid? Wowza!
When Should I Use Fancy-Pants Sea Salt?
In all honesty, you don't have to ever use the stuff. Then again, you don't have to, say, watch Ghostbusters. Neither is essential to survival, but both make life more worth living.
Fancy salts are harvested from oceans and salty rivers and lakes around the world. Depending on exactly how they are formed and the trace minerals they contain, their shape can range from moist, clumpy chunks to pyramid-like, lacy flakes, with colors ranging from bright pink to pitch-black.
While the differences in color are largely cosmetic, shape can have an effect on a salt's eating qualities. Chefs like using sea salts because they provide crunchy texture and a burst of salinity that adds interest to plated foods. They should be used exclusively for finishing dishes. Scattering on the tops of glazed loaves of bread before baking. Sprinkling over sliced perfectly cooked steak just before serving. Adding a touch of crunch to slivers of raw scallops. You get the picture. Fancy-pants food.
If you're using your fancy sea salt to cook with, on the other hand, you may as well replace your toilet paper with dollar bills, because you are flushing all of its good features down the toilet.
As for the question of relative cost, I did a quick online search and found that kosher salt prices are, on average, about 20% greater than table salt prices when you buy both in bulk. Hardly a bank-breaker, especially when you consider first that whether you buy regular salt or kosher salt, in any given dish you are likely to be using a mere fraction of a penny's worth. For me, the convenience and familiarity of having only one type of cooking salt is worth that slight extra cost.
Many table salts have had trace amounts of iodine added to them. This practice was started in the 1920s in order to help battle goiter, a problem that was rampant in the American North, from the Great Lakes to the Pacific Northwest. These days, goiter has been all but eliminated in our population due to iodized salt, though it still appears in parts of the world where iodine deficiencies are common.
Do you need to use iodized salt? Chances are, probably not. Fish and seaweed are the best sources of iodine, but most vegetables contain iodine, too, as does dairy. As long as you are eating plenty of vegetables and/or fish, you'll get the iodine you need, even if you use only kosher salt.
As for the flavor, it's mostly undetectable in table salt, though some folks who are particularly sensitive to it might notice it in more mildly flavored dishes.
Get a Salt Cellar!
Having a salt cellar in a prominent spot by your prep station or stove is a constant reminder to taste and season your food as you cook. I guarantee that if you don't already have one, putting a salt cellar on your counter will make you a better cook. Any covered container with a wide-mouthed, easy-open lid will do, but the RSVP Salt Server does it with style.
What Do I Recommend?
At home, I have a salt cellar that's filled with Diamond Crystal kosher salt. I keep it by the stove when cooking and transfer it to the dining room table during dinner. I also keep a small supply of various coarse sea salts of different textures and sizes, which I use to finish dishes. The two I most commonly use are Maldon sea salt from England (I love its lacy pyramids) and fleur de sel from Guérande (nice large, crunchy crystals that will stay undissolved on sliced meat until you bite into it). I don't keep table salt at home.