Salt, you know, blood pressure raising good tasting white poison death!
Before we go down the rabbit hole, unless otherwise specified we use table salt, we weigh it and we add it to the mixing bowl with all the other ingredients. That said....
As you probably know, salt is at the heart of a number of controversies. Chef's tell you that most people don't use enough and that too much is just enough to paraphrase Mark Twain on the subject of whiskey, Doctors tell us we use too much of it. Salt does improve the flavor of foods. Salt does raise blood pressure for sensitive individuals.
That's just the start of the great salt debates. Many people don't like the taste of iodine, but without it many people risk thyroid issues.
And then there is the debate between people who use just plain salt and fancy salts. Can you taste the difference between salt mined in Utah and salt laboriously puddled in the salt flats of France? Some people say salt is salt and you can't. Others say due to minerals in sea salt, you can taste the difference. There are salts that have been smoked or otherwise flavored. Yeah, the difference is obvious. Since our focus is on bread making, I'm not sure I want to use a smoked or lemon infused salt in my bread. It might be nice, and maybe I should try it.
There are also salts which taste different due to their crystalline structure. A fine grind table salt gives you a different taste than a fleur de sel. Try both on a steak or veggies, you'll be a believer! Sprinkling some sea salt on a nice slice of bread that has been slathered with good butter is delightful and you can definitely taste differences between salts! However, when you put salt in the water you use to boil pasta or make bread, the salts are dissolved and with that, the differences between the salts is also dissolved. Our view is we like a plain sea salt. Not iodized. And as cheap as we can find. We save the good salt to use as finishing salts on the table. If we wind up with a very coarse salt, we'll dissolve it in the liquids we use to make bread (usually, but not always, water).
Kosher salt is another topic of debate. Many people love it, and it is called for by endless TV chefs. Many people like it because they know "kosher" foods are "healthier". This comes from a misunderstanding of what kosher salt is. It is used in slaughtering animals to efficiently drain blood and other fluids from the animals. Salt draws fluids. The grind, or crystal structure, of kosher salt makes it good for this purpose. The people who love salts typically do not like kosher salt because it has been purified to the point where it has no taste.
Overall, for our purposes as bakers, salt is salt. I've only heard of one case where it isn't quite so. In a baking echo on FidoNet many years ago, someone said as soon as he switched to using a wet French salt his recipes stopped rising. We didn't know why since we'd never even seen such a salt, so our practical advice was to stop using that salt and see if things get better. He did and they did. Again, save the fancy salts for use as finishing salts.
We're not going to weigh in very much on those fraught debates, we'll just focus on salt in baking and how to measure salt.
Salt acts as an antioxidant in dough, helping preserve the cream color of an unbleached flour which could otherwise be lost in kneading. Salt helps build gluten and also moderates the activity of yeast. Too much salt will kill yeast, and a large part of a sourdough starter is yeast. This has led to debates about when to add salt to the dough. Some people want to add it early to protect the caretenoids that give the flour its creamy color. Others want to add it late to keep the gluten from developing too quickly. Professor Calvel looked at this in his book, "The Taste of Bread" and said he couldn't see enough difference to make a strong recommendation. He said the main thing is to make sure you DO add the salt. The best bet is to taste a bot of the dough. If you left out the salt, you'll know at once. You could also print copies of your formula and check off the ingredients as you add them.
Finally, how do we measure salt? Many people say that kosher salt has less sodium than table salt. And that's not entirely true. I've gotten into arguments with chefs over this. Because kosher salt is coarser than table salt, less of it will fit into a teaspoon. A teaspoon of coarse salt is less salt than a teaspoon of finely ground salt. If you use less salt, you have less sodium. If you measure teaspoons of salt, you may notice differences in your breads based on the salts you use. If you measure by weight, the differences in the amount of sodium are negligible.
King Arthur Flour has a very handy ingredient weight chart. and it has the following information:
Salt Weight in grams per tablespoon teaspoon
Salt (Kosher, Diamond Crystal) 8 2.66
Salt (Kosher, Morton's) 16 5.33
Salt (table) 18 6
And those changes are just due to the coarseness of the salt.