Swamprb's idea of using Gasket Cement is interesting. The "Imperial" brand I used dried up harder and stiffer than their furnace cement. So, it might be less prone to bubbling.
However, I think the main thing is to drive off ALL the moisture from the furnace cement (or gasket cement) before it cures permanently. That way it shouldn't be able to bubble anymore.
If I were to do it again, I would prefer to do cure the firebox in the oven because the temperature is easy to control but I'd still have to cure the cement on the cooker. However, my sweetie absolutely said the oven was off limits for this.
So, in hindsight, I ramped up too quickly too fast.
To begin with, my starting temperature was too high (too close to the boiling point of water, 212F). Steam was created and got trapped, bubbling the uncured cement. Need to start lower and hold it there longer to drive off most of the trapped water before going higher.
OSX's idea to start at 150F would be a lot safer. Next time, I'd probably stay at 150F for at least 4-6 hours. Then bring the temperature up slowly. The key word is SLOWLY!!!
Say 2 hours each at 175F and 200F, 4 hours at 225-250F, 3 hours at 275F, 3 hours at 300F, etc. Probably do this twice before going to higher temperatures.
For my next firing, I'll still keep my temperatures low because I'm pretty sure the cement hasn't fully cured (didn't go above 330F). Will still be careful to ramp up slowly though.
I can live with cement bubbles in the firebox, but would prefer not to have any more in the Kamado itself (especially, big ones).
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