I bought an old kiln (cone art) to use at my summer cottage, and retrofitted it with new elements and a new electronic controller. The interior bricks are in excellent condition, but the lid has several small cracks. After firing it a couple times (bisque and cone 6) I see that it is losing a lot of heat, likely through the lid. I leave a window open during firing - but the room is super hot - so hot that I'm afraid it's actually a fire hazard. I can see a glow between the lid and top of the kiln when it's reached temp. (pieces in the kiln fire well, generally - although during the last glaze firing two flat platters on the top shelf cracked - so I'm assuming it's cooling too quickly. Only the top shelf has this cracking problem).
I've read a lot of stuff about this - some people use fire blankets (sounds scary). I was thinking of putting an old kiln shelf on top while firing, to try to keep the heat from escaping. This might be a dumb idea because of the weight on an already fragile lid. Am thinking of getting a new lid. Would love to hear some advice here.