I’ve had a box of kosher salt in my cupboard, but haven’t used it in a few months. I just took it out and the entire box is soggy . . . not to the point of falling apart, but not far from it. I was able to pour out enough salt for my immediate need, but I don’t know what condition the rest of the box is in.
So what caused this? Nothing else in the cupboard is affected this way, including other kinds of salt. And can it be fixed, and what can I do to keep it from happening again?
Salt is hygroscopic and will absorb moisture out of the air (or whatever you’re cooking, which is often what you want). The shape and size of the kosher salt crystals make it especially suited for this. It does happen to the other salt in your cupboard, but it’s not so noticeable and they don’t absorb it as readily.
What it means is that the humidity is probably too high where you’re storing your salt. In fact, there’s a commercial product, “Damp-Rid”, which is nothing more than calcium chloride (also hygroscopic) in the same sort of flaky crystals.
Keep the kosher salt in a sealed plastic bag to protect it, or try to control the humidity where it’s stored.
edit: And sorry, no, it can’t be fixed at this point; it’s already dissolved and formed new crystals.
Spread it on a pan and put it in a warm oven until dried out. Throw it out if it’s now a solid sheet of salt. store the salt in a jar and seal it tight. Put smaller amounts in a container to use regularly.