The fate of many kinds of french fries, it seems, is to undergo some strange transmutation into a gritty substance having the taste and texture of soggy cardboard 
Some kinds of french fries seem particularly prone to this (In and Out Burger). Reheating them does nothing to restore either the flavor nor the texture.
What exactly is going on in the fries that takes something tasty and crispy and turns it into a soggy, bland leftover?