Why do some people suggest not using iron or steel crucibles?
After a awhile the iron or steel crucibles begin to erode and flake apart. The molton aluminum (or bronze, etc.) can absorb some of this iron which will weaken the castings on a molecular level. It’s usually said that on the typical backyard hobby quality this is no problem and is not even noticeable. But when attempting to keep the metals as pure as possible (i.e. when making high quality ingots, special alloys, or structural/mechanical parts) a ceramic crucible is best.
