Cracks & leaking smoke

[pipittenger]

Just fired up my new pizza & bread oven. I'd finished it last fall & worked it up to temperature gradually over 2 weeks. Used it three times, then wanted to change the tilt of the entry way and had to wait until spring. So now I've finished fixing it and lit it up for the first time, and noticed that there was some (not a lot) smoke coming out of the center of the roof. I thought it might have been doing that last fall, but had forgotten about it.

Looking inside, I see there is a crack front to back of the dome of the top, and one from that crack down to one side. I built the sides of the oven with fire brick but purchased a pre-formed dome to cap it all. It's the pre-fab dome that has cracked.

1. Is this a problem? (It can't be good for insulation.)
2. If so, what can I do about it, if anything?

Needless to say, after so much work (5 years in the making, I'm embarrassed to say) this is producing a lot of anxiety!

If there's already an answer out there, just point me in the right direction.

[david s]

Re: Cracks & leaking smoke

The fact that the dome has cracked should not be too much of a problem because as it is a dome it will be self supporting even if it cracked into several pieces it can't collapse. You don't say whether the dome is one piece or a few, but any large pieces of refractory are subject to cracking so a number of interlocking pieces are preferable IMO. The cracks you have now got have simply created those pieces where they want to. Regarding the leaking smoke, you do have an issue because as you say you will be losing heat. If you have leaking smoke then presumably you don't have any insulation over your dome or perhaps you also have cracks in the outer shell in which case will provide an entry for water to get in by.Can you post a photo?

[pipittenger]

Re: Cracks & leaking smoke

Thanks for your replay. I'll post a photo later, but I have the oven under an open-sided sort of shed. No rain or snow will get directly onto/into it, though I suppose it might under extreme, blowing conditions. You are right, the outer layer is also cracked, and I assume the insulation is cracked as well since the smoke gets out. I made many layers of vermiculite/Portland to create the insulating layer, which is around 5 inches thick.

[david s]

Re: Cracks & leaking smoke

Plug up the cracks in the outer shell and render over them. Try to keep that new layer damp for a week by covering with plastic. Forget the cracks in the inner dome. Any attempt to fix them usually results in failure.

[pipittenger]

Re: Cracks & leaking smoke

Thanks -- I'll see if I can stuff more insulation down in -- maybe widen the crack a bit -- and then cover it with the stucco. Will keep it moist and won't use it for a couple of weeks, then will bring it up to heat slowly. Sound ok?

Here are pictures.

[pipittenger]

Re: Cracks & leaking smoke

Those photos didn't show up very well, so here's a link to an album that shows all three:

imgur: the simple image sharer