Why does Parmesan curl when planed?

If US people call all this type of cheese “Parmagiano”, that’s what I mean here.

I have been using my cheese planes a bit lately. I’ve tried it on gruyere and cheddar, and they’ve cut and sat flat. But Parmesan curled up when planed, even with my pretty thick plane.

This is young parmesan (maybe six months) , and the gruyere was 3 years old.

I’d assumed the slightly curled bits of parmesan you get in salads were like that because they were produced by drawing a sharp knife along the surface of a block of cheese - much as you would to curl a ribbon. Indeed, I’ve seen cooks do that on the TV. But it seems it curls anyway.

My guess is that the heat caused by the friction of the planing releases oils in the cheese, and the remaining bit curls because of it as it draws together. Sort of the same way a a fatty steak or pork chop will curl if you cook it too fast.

Maybe another factor is the exposed surface of the cheese is slightly drier, and is trying to shrink, though held in place by the rest of the block. When you shave it off, it can now shrink by pulling the strip into a curl.

I have no idea if this is actually what’s happening.

Don’t most dry-ish things curl when planed? Chocolate, wood, etc.–they curl up too.

It curls for the same reason that wood does - the mechanical force of the plane bends the cut portion upward.

Softer cheeses undergo the same force, but they are more plastic and won’t hold the curled shape.