After one-week of air-drying the 9 lbs of furnace cement, Humpty got put back together for Bakeout #2 on the weekend.
Both Swamprb (BGE Rescue
) and Jim Beam reported the furnace cement bubbled with heat on their repairs, so I decided to keep the bakeout LOW and SLOW.
For Bakeout #2, Humpty got cured for about 8 hours total (2h at 220F, 1.5h 250F, 1.5h 300F, 1h 330F, 1h 250F 1h, 200F, etc.) till the coals died.
Darn it all, the furnace cement still bubbled!!!
Which means I was still too agressive with the heat.
Even after air-drying for a week, the furnace cement still had residual water. When heated too fast, the water gets trapped as steam in the cement, causing it to bubble.
Most of the bubbles showed up in the firebox.
Thank goodness - no bubbling of the cement in the Dome. But one big bubble inside the base right under the charcoal grate.
Will see if I can flatten this one by putting a weight on the base for the next firing.
An interesting FYI... Before the bakeout, I used a heat gun to dry a small patch of cement on the base. Lo and behold, a bubble formed, but it was quickly squished flat with the thumb while still hot. Don't even try this with charcoal!!!
Well, Humpty the Copper Cooker seems to be intact again. Will do some low temperature cooks and and see if the furnace cement bubbles some more or if new cracks appear. Keeping my fingers crossed for now!
Project Humpty: SLIDESHOW
, PHOTO ALBUM