#1  
Old 04-26-2005, 02:18 AM
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Join Date: Mar 2005
Posts: 239
Default Dome cracks

We lit our first fire and found a tiny hairline crack on the
claddign around the oven. Should I fix it? How, with Concrete or
something more flexible?

Aesthetic question...
The bricks I got have cores in them which is fine for stacking but I
am not sure how to finish of the top so that teh holes don't show.
On the chimney, I will likely stand the last row on end but what
about the front facade that doesn't go as high? Any suggestions?
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  #2  
Old 04-26-2005, 02:19 AM
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Join Date: Mar 2005
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The cracks are no doubt due to expansion and will expand and contract with
each firing.
As long as they are only hairline, no need to repair. Since they almost
disappear when
the cladding returns to room temperature. As long as the inside bricks have
been properly
mortared you shouldn't have any leaks that will be a cause for concern.
If you see smoke coming out the cracks, this may actually be water from the
concrete or
mortar being vaporized because of the heat. This may have added to the cause
of the cracks
in the first place.
Have several more firing before you insulate and close in the dome. Monitor
the cracks to see
if the continue to grow in width.

Jeff
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  #3  
Old 04-26-2005, 02:20 AM
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My vent area leaked smoke in 3-4 places on my first outdoor mailbox
oven. I just let it fully dry out, then covered it with a second
layer of refractory mortar. Then, as Jeff says, I made sure the whole
assembly was smoke-tight before I moved on to insulation and my
finish walls.

Has anyone ever pointed their infrared thermometer at the vent
masonry when the oven it hot (I don't have a gun here). If the oven
floor is 700F +/-, how hot is the vent right about the oven opening?


James
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  #4  
Old 04-26-2005, 02:21 AM
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It's not a problem. Wait until you've used it a half-dozen times. That
will dry it all out and any cracking will be at max. Then fill it with
furnace cement (you can get it in caulking tubes). Fire the oven after
filling the crack(s) and keep filling in any expansion that occurs as
it heats up. One of the advantages of the Pompeii design is that all
of the brick front edges mate without mortar joints inside the oven
which will keep it structually sound despite any cracking. (If you
want you can make a V groove along the crack to open it up enough to
get the cement into it.) Cracking is why you insulate with a fireproof
material like vermiculite -- no chance of it catching fire.

Jim
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