Both suggestions suggest how to anneal, thank you. I have done that and am waiting for it to cool down. My real question is why is the metal not soft after it cools down after casting?
Another question. I have watched a number of videos of metal being forged, as it is done large amounts of slag, I think that is what you call it, falls off. I have just been trying to clean my mild steel crucible after casting the bronze. As I did it a lot of slag fell off the outside of the crucible, what exactly is this slag? It measured 0.8mm thick, quite substantial, but the crucible still has its integrity.