[DaveHI]

Welcome to the club.

on about firing #3 my arch crack appeared. I didn't have my IR thermo yet so no idea if I just over fired it too early or if my brickwork was sub par. I had tried to cut tapered bricks to minimize the size of mortar joints. Getting the Italian mortar to Hawaii wasn't cheap and I knew i'd have to be careful or come up short. Between those cuts not yielding uniform pieces and poor joint thickness control, half brick stagger from row to row didn't hold up from the middle of the back around to the front. Had some too close from row to row. I should have cut some larger blocks to get the stagger back but didnt realize it would be an issue.

My thermal crack started about the middle of my arch and snaked all the way up to the top of the dome. At the arch it was big. I could see fire easily and I'd guess a quarter would have fit in the crack. The rest of the way it was just a crack with no smoking etc. I fired the heck out of it a number of times to see just how bad it would get.

Once it stopped growing, I v notched the crack with my angle grinder and diamond blade. I ordered furnace cement (black goo) and fireplace mortar repair (tube of caulk like material) from Aubuchon Hardward (mainly because they will ship via US mail to Hawaii so the freight only doubles the bill instead of 5X like many of the other sources).

I then fired the heck out of it, pushed the black goo into the crack as far as I could get it and filled the visible crack with the mortar repair. Both need 500 F firing to set properly so I hit the front face with my plumber's torch to make sure it set hard. I then let it cool down and slathered an inch of homemade high temp mortar on the cracked area and the rest of the dome for good measure. Seems to have worked. I've seen no smoking in the enclosure or discoloration of the insulation. Nor do I see/feel hot spots on the insulation.

Not to mention it holds heat very well and I've no prob hitting 1050 dome temps.

Total cost -- about $25 bucks for the various furnace goos including high priced shipping.

Good luck! As long as you aren't indoors and your surround is fireproof it's mostly just aesthetics. And near as I can tell, your friends just want to eat the pie!