dailyplots

Hello I purchased an old Hoskins induction furnace model fd 104 5 inch bore 5 1/2 inches high.I have searched fro some information regarding the proper size crucible I have silicone graphite a5 bell crucibles, but after a couple of pours from a crucible I tempered melted some cans; it is destroyed and unsafe to use with cracks. I need to know if you place a small stand or buffer from the bottom of the induction furnace? I have read that silicone graphite crucibles are best,but would like someones opinion on the proper size of crucible type for this specific model, I confess that the model is fairly archaic had to replace a power cord. Also should I build a cover to achieve higher temperatures if so vented non vented? All in all happy i didn't hurt myself having read up on proper procedures and having used safety equipment. I have a few aluminum bars for my effort, thanks for any help from a partial neophyte on this subject.