Not All Salt Is Created Equal
If you’ve ever taken a basic chemistry course, you know that what we usually call “salt” is just one type of salt. Salt is simply a chemical compound made up of a positively charged ion (cation) and a negatively charged ion (anion). The salt we usually sprinkle on food is sodium chloride – NaCl if you’re a weakling – and it makes food taste good.
Pink salt, black salt, red salt and the like – they all take on their color from tiny, largely insignificant amounts of minerals and other impurities, or at least things that would be considered impurities if you were trying to crystallize pure sodium chloride. Yes, a lot of table salt contains iodine, but only 45 micrograms (0.000045 grams) per gram, which – for our purposes – is not enough to worry. (Some people who avoid sodium for medical reasons season their food with potassium chloride, but I’ve never tried it.) But even in the colorless sodium chloride realm, there is one big difference between salts that can affect your food and cooking: Crystal size …
Table salt, for example, has a compact crystal structure; the grains are tiny, ordered cubes. On the other hand, the scales of something like Maldon are thin, spreading pyramids. The first fits into a teaspoon much more easily than the second, so interchanges don’t make any sense if you’re measuring volume. This is why it is very important to pay attention to the type of salt indicated in the recipe. If a recipe calls for a tablespoon of kosher salt, using a tablespoon of fine sea salt or table salt will result in an overly seasoned dish as kosher salt has a much larger crystalline structure than either of the other two.
If you don’t have the salt in your recipe, or just want to use a different salt, measure it by weight. You can find tons of most of the salts on the Internet quite easily, so just type in “how much does a teaspoon of grade X kosher salt weigh?” into your browser (different brands may have different weights), check the weight, and then weigh that amount of salt you are working with. The impurities in pink, red, and black salts may confuse your calculations a little, but they are better for finishing anyway – cooking with them hides the light, so to speak, under the bushel.
Updated 3/24/21 at 11:40 AM PST to clarify how to look for salt mass.