i've been working toward being able to cast, last week I got around to making 10x11.5x5.5 cope and drag. I made a foam pattern and plan on trying to cast a pulley blank from zinc for another project. So along the way of getting ready to cast, i pulled the furnace out and inspected the lining and it appears that it has blown out chunks of refractory in the lid for some unknown reason, the only thing holding it in is the wire fence that I welded inside prior to packing the refractory. But it has an air gap of roughly 1/4 to 1/2 inch in some places.
This failed pretty bad it could be rebuild but the blow out concerns me if it does this after 3 firings (first 2 firings were for driving moisture out and 3rd was when i was using the foundry to make crucible tools from rebar) what happens after 6 does it drop into the crucible and cause damage to refractory lining!
I'm thinking of doing the gingery lid using sheet metal and fencing wire, but I don't know what is going to keep the same thing from happening to the next lid??
