Well, it's not exactly the safest chimney to begin with:rolleyes:, but it has a crack that needs filling or else smoke will leak. I think, if I had a long slice, I could apply mortar, but anything else (concrete crack filler?) would be easier.
I have made many fires in it so far, and gotten them up to welding heat:D. The chimney and everything around it holds up fine. Still, one crack bothers me...
Oh, could I put a little concrete crack filler near a fire to test it's flammability (like put some on the forge's wall, and let it dry, then build a fire)?