Lessons Learned from "Project Humpty"
I'm currently at what I hope is the tail end of a restore of an old clay egg (red clay). Humpty's internals were all cracked through so they were in pieces. The dome was cracked in a few pieces, but held together with wire. The bottom was cracked in pieces at the rim, but not through to the base.
The refurb seemed relatively straightforward. In what I now call the Phase 1 repair, I skimped and only used 1 coating of JB on all the cracks. However, new cracks appeared only after the second firing. Dissasembly after the 4th firing showing that the JB had disintegrated completely in the firebox. I suspect this is due to the extreme heat generated by the coals.
The JB welds seem to be holding in the base and the dome, but there are a couple of little weld pits in the dome where the JB has pooled, which I suspect is due to overheating. For future firings, I know I have to watch my dome temperatures, since JB is "temperature resistant" to 500F. Otherwise, I'm sure all the JB welds in the dome will break down and disintegrate.
The Phase 2 repairs are still ongoing, but here's what I've learned if you need to get your hands dirty:
- Don't use JB in the firebox or any areas that will be subject to heat above 500F. Try a high-temperature furnace and gasket cement instead. JB should be OK in areas that do not see high temperatures above 500F.
- To stop crack propagation (new cracks growing from old ones), consider drilling a small hole at the end of the crack. Do this before applying any epoxy or cement.
- Don't paint the egg until after proving your repairs with several low and slow fires. In my case, new cracks showed up in my newly painted egg only after the second firing. I had to scrub the new paint job off to repair the cracks.
- Keep your first few firings low and slow. Don't subject the egg to rapid changes in temperature. Especially watch your temperatures while the coals ash up.
CaptnGrumpy may be right in that the older eggs cannot be used for cooks over 550F. I didn't cook at 550F, but temperatures did exceed 550F only ONCE for a few minutes during my 4th firing. I'm sure the high heat disintegrated the JB and also created the extra thermal stress that cracked my egg further.
Project Humpty is still ongoing and the thread postings may be a good resource if you will be doing repair work.
Good luck on your new egg!
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MayDay
Project Humpty:
SLIDESHOW,
PHOTO ALBUM
Kamado/BGE, Cobb