Well, last time I made mozzarella, I tested with a few curds and they got a nice stretch. So I figured hey. I tossed the curds into the hot water and started kneading and folding. They wouldn't really stretch, and fairly soon half of it turned to ricotta. So I had these round balls, with veins of firm mozzarella surrounded by crumbly ricotta. I think this might have been one of two things. Either I stirred too much and broke the curds too much. Or the more likely problem was that I, not thinking, poured my curds into the colander, so the first third or half shattered before I could stop and put the rest in with a slotted spoon.