Introduction
We recently discovered that the firebox in our medium Big Green Egg cooker had broken into a number of pieces. We chose to repair the firebox using J-B Weld (pictured at right). We chose JB Weld becuase it is easy to use, will survive temperatures up to 600°F, and once cured, forms a compound that is inert and safe to use in a ceramic cooker. So we thought we'd document the process for you to show you how you can make these same repairs.

J-B Weld is a cold-weld compound, consisting of two different tubes of material that you mix to form the final product. One tube contains a liquid steel/epoxy resin, while the other tube contains a hardener. Once mixed, the two materials undergo a chemical reaction that results in a compound advertised to be as hard as steel and resistant to heat up to 600°F. It sets in 4 to 6 hours and is fully cured in 16 to 24 hours. Once fully cured, the resulting material is inert and safe to use to make repairs. (See the safety section down below.) You can read more about JB Weld at their website.

The subject of this operation is the firebox from our medium Big Green Egg cooker. When cleaning out the ashes, we discovered a crack in the side of the firebox. When we tried to lift the firebox out of the cooker, we discovered that the crack went all the way around the firebox. The top half separated from the bottom half, the bottom half fell back into the cooker, and broke into six pieces. Here is our poor broken firebox lying on the ground:

UPDATE: Does it smell? We were alerted by a reader to the fact that cured JB Weld material may emit an odor once it is heated above 400°F. We hadn't noticed any smell while heating up the firebox initially, but we respect this reader so we decided to look into it further. Here's what we did and what we found out: Once the firebox was cured, we lit a small fire in our cooker and let it burn out. We never smelled anything but charcoal/smoke during this burn. After the cooker had cooled down, we burned a full firebox of charcoal with the vents wide open. Again, during this process we never smelled anything but charcoal/smoke. We did a third hot burn and yet again, we smelled nothing other than charcoal/smoke. At this point we began to wonder if any odor being emitted by the JB Weld was being totally overwhelmed by the smell of charcoal/smoke. So, we placed the firebox in our oven and heated it up to 450°F. We noticed a slight chemical smell. Of course, by this time, the firebox had been heated up four times, so we decided to try again with some freshly cured and unheated JB Weld. We mixed up a batch of JB Weld in an aluminum foil pan and let it cure for 36 hours at room temperature. We then placed said pan in our oven and set the temperature to 300°F. No smell. We bumped it up to 400°F and began to notice a chemical smell. Finally, we bumped the oven up to 500°F and sure enough, the smell became quite noticeable. So clearly, the smell of the burning charcoal was able to totally obscure any chemical smell from the JB Weld itself. Our next question was how long this smell might persist. Is it possible to heat the JB Weld and "drive the demons out"? So we let the JB Weld cool and sit for another 24 hours before once again heating it up to 500°F. Sure enough, after 3 cycles of heating the cured JB Weld, the smell was almost gone. So yes, JB Weld will emit an odor when heated, but this odor will disappear after a period of heating over 400°F. So again we conclude that JB Weld is indeed safe to use and again we will point to the fact that JB Weld only cautions about letting food come into direct contact with the cured material because they haven't tested it for food safety. .