Copper cracks when I roll it

I have been trying to roll some copper ingots into wire and sheet metal. It has a tendency to crack and split as it is rolled. I don’t quite understand why as pure copper is supposed to very malleable. Is it simply that it must be Annealed more frequently than sterling silver? Am I introducing oxygen when pouring the ingots somehow making them brittle?

Turn out my copper was just impure. I tried rolling some copper that was .999 pure and it rolled just fine with no cracks.

I roll a lot of copper wire and sheet and it rolls just fine. Make sure that you are really rolling copper and that you anneal often…Rob