Crucible size and surounding space size for furnace ?

Hi Phil
A good general rule is 2.5" to 3" of clearance between the crucible and furnace wall and 3" below and above the crucible
to achieve good combustion if you are going to melt cast iron or bronze , you can get away with allot less clearance for aluminium.

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Thanks Rob, excellent info, :bow: although it does bring up more questions in my mind.

I have read that refractory makes a pretty poor insulator, so I was going to line the inside wall of the old gas bottle with the white wool type insulating material that is about an inch thick (not wool but a high temp material) then cast the refractory on the inside of that. The refractory is the commercial stuff.

As a rule of thumb what would the minimum thickness needed to be to withstand melts for bronze of iron?
Although I do only intend to do aluminum at this stage, the info would be good for a larger furnace later as well.

The question comes about because if I use the correct combustion gap this will deem the final crucible size.

ps. The gas bottle has a 12 inch diameter and is 11 inches high (although 1 1/2 inches of that will be the lid) . I was planing to put a 3 inch exhaust hole in the top. No thoughts on the burner yet.

Phil

Thanks Rob, excellent info, :bow: although it does bring up more questions in my mind.I have read that refractory makes a pretty poor insulator, so I was going to line the inside wall of the old gas bottle with the white wool type insulating material that is about an inch thick (not wool but a high temp material) then cast the refractory on the inside of that. The refractory is the commercial stuff.As a rule of thumb what would the minimum thickness needed to be to withstand melts for bronze of iron?Although I do only intend to do aluminum at this stage, the info would be good for a larger furnace later as well.The question comes about because if I use the correct combustion gap this will deem the final crucible size.ps. The gas bottle has a 12 inch diameter and is 11 inches high (although 1 1/2 inches of that will be the lid) . I was planing to put a 3 inch exhaust hole in the top. No thoughts on the burner yet.Phil