1 Tsp. of finely ground salt has a much different impact than 1 Tsp. of course ground salt. I am not going to pretend to know the science behind this so I am going to stick with my own explanation of why this is the case. The two main factors I see are the breakdown process – the way it dissolves and distributes through the dish, and the potency level.
With fine ground salt, what you see is what you get. If you have been using fine ground salt your whole cooking life than you have developed some sort of gauge for how much is too much. Even if you aren’t consciously keeping track of it every single time, the information is still being tracked and tallied in some way – your collective pool of salt wisdom grows every time you use it. If you apply these parameters to course ground salt you are going to get an unpleasant surprise.
The general rule with salt is – you can always add more but you can’t take it out. It’s a good habit to add slowly and taste before adding anymore; this is where the difference between fine and course ground is most prevalent. Fine ground salt dissolves and assimilates very quickly; you add it to your marinara sauce, you stir a little and taste – and this will give you an accurate reading. After that same stir, course ground salt has not even begun to fully incorporate into the sauce. The little granules are slowing dissolving and more and more salt is releasing. Not only do those granules release slowly, but the salt itself is generally more potent; not being aware of this can ruin a dish in a matter of seconds, and it will be the final seconds of the cooking process.
This is a hell of a way to go out; you spend four hours making an incredible sauce with ingredients you bought from the farmers market and it is turning out to be a masterpiece. Who knows who you are cooking for – maybe a hot date, your in-laws, yourself, and all it needs is that final touch of salt.