I tried to cast iron, I still had an old crucible somewhat worn out from earlier melts of cast iron, so this should be its last use. I melted it and heated to 1400 C in a forced draft propane furnace but when I wanted to take the crucible out, it was softened and cracked so I did not want to pour, but it was already too late. Iron was leaking out of the bottom, but it stopped due to freezing. I dumped the hot crucible with the frozen iron into a bucket of water and then I shattered the crucible, so I could reclaim the bum of cast iron. So I have to repair the furnace and I've learned a lesson. It was a cheap Amazon crucible. Suitable for copper alloys, but ferrous is a no-no. I'll only use the real Morgan Salamander crucibles, I already have two and one on order. Here a short clip what I saw after shutting down the furnace and opening the lid. https://www.metallab.net/jwplayer/video.php?f=/forums/requiem-for-a-crucible.mp4
