Small cracks in vent

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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

>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
>
>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?