Herbie-
I have been following the path of fellow HMEM member Rob Wilson (also on MadModder), and he is UK based.
Rob has melted cast iron with a forced air burner, and his comment was "it is hard on crucibles".
I don't know if he meant it is hard on ferrous metal crucibles or on non-ferrous rated crucibles (or maybe both).
The clay based crucibles made by Morgan are ferrous-metal rated, and the silicon carbide are not. Unfortunately, both are labeled Salamander, but one will work with cast iron, and one will not. (See photo below).
I think the clay will be black in color, and the non-ferrous will be a color other than black. Note that some silicon carbide crucibles are also black, and not ferrous-metal rated.
So far, I have only melted aluminum, but am working up towards cast iron slowly.
I have a 100 lb. propane tank, and don't use forced air, and so far, the tank has not been able to maintain the propane pressure that I think I need to melt cast iron, since the tank gets too cold, and the vapor pressure drops to maybe 10 lbs. or less.
I am told that a cast iron melt may take an hour or so, but with an efficient furnace, that should not be more than 10-15 lbs of propane.
I am building a crane to lift the crucible, and a pouring shank with wheels to keep me back from the cast iron crucible, since they have a lot of radiant heat, and also would cast an extreme amount of damage if they ruptured near you when you are pouring.
For small crucibles, it is not too bad (see YouTube backyard cast iron casting).
I plan on getting another 100 lb. tank and trying gray cast iron again this summer.
Also note that the larger crucibles are heavy, and when full of metal will have to be handled with a crane, since they may exceed 150 lbs. including the weight of the pouring shank.
