March 24, 2011 - 7:46am
mortar to patch a opening in brick oven?
I have a small opening where the ceiling and the wall of my brick oven meet. Does anyone know where I can get a substance that I can use to patch it up? It must be able to withstand temps as high as 900 degrees.
How big is the hole you are trying to patch? If not too large you could use a home made mortar consisting of 10 parts sand, 3 parts portland cement, and 1.5 parts fire clay. This is the mixture I used to construct my AS style oven.
The Forno Bravo go-to mortar mix is 3 sand 1 cement 1 lime 1 fireclay. Some use 2 fireclay. I have a mason friend who says when he does flue tiles for a chimney he uses 4 sand 2 cement. There's also a high-heat caulk that you can buy at fireplace supply outfits. I think you could do all kinds of things, and if it cracks out after a couple of years, do it again.
I'm a senior member on the FB Forum. As Polo says, it really depends on the size of the hole/crack. Joints in a WFO should be no wider than 1/8" at the best of times to reduce direct exposure to flame. You could either make up your own mortar mix as directed, or you could use SuperWet 3000, which comes as mix 26 (thinner, for cracks) or mix 22 (thicker, for larger holes). Problem with this material is that it only comes in 50lb pails, I think. Alternately, and as a last resort, you "could" use commonly available furnace repair cement. It will withstand the temps, but it's not easy to work with and not very handsome when dry.
Go to the chimney/wood fire stove section of your hardware store and get a good measure of sealing rope for wood fired ovens. This can be jammed into the crack with a spatula or flat screwdriver and be twisted for added thickness and rope allows for a little expansion as well. I would also try using flue repair cement if the crack was larger. Check ingredients list before purchasing.
All the responses give good information, but none address the underlying issues. (Nor does your question.) Before patching a crack, you should first address the issues that caused the crack in the first place -- otherwise, it will likely simply return after patching.
And just for the record, your patch will need to withstand heat far in excess of 900°. That may be the surface temp after firing, but to get there, the fire produces much higher temps. The temps in my WFO during firing are in excess of 1,200° -- the maximum temp my infrared thermometer will read.