curing, craks and vermiculite

[mrgweeto]

Well we got our oven up to the 500 degree temp tonight. We put in 42 cuft of vermiculite which gives us 6'' or better all around the dome inside the inclosure. Before we did that we put a drop light inside prior to the fire and checked for cracks. Found none. We did see some cracks on the outside of the dome in the Heatstop coat. We put 2 coats on. One last one after the dome was complete. In all honesty several days after the final top coat was added and way before any matches were lit we did have some cracks from drying out and shrinking. While the fire was going tonight we checked to see if we saw any steam or smoke coming from the cracks and there none. the cracks were actually the furthest away from the flames. When reading the temp the hottest it got on those side walls so far was about 300degrees. The hottest the dome on the outside got at 500 degrees inside was only 108.
Is it safe to assume that the cracking on the outside is pretty typical and we should not worry. Remember that there is no cracking on the inside in the bricks or the mortar joints that we could see..
Any thoughts are appreciated.
G

[Les]

Re: curing, craks and vermiculite

You didn't mention how large the cracks were, but yes, we all have them. Even if they appear on the inside, I don't see how it will be a problem. Cover it with a blanket and call it good.

Les...

[mrgweeto]

Re: curing, craks and vermiculite

Les,
The picture on the 2nd page of your album labeled "first fire" appears to be a little longer and slightly wider than our biggest. We have onein the same location and one that is horizontal several courses up. I'm not too worried so we poured 6/6cuft basgs of medium vermiculite in the enclosue and closed up the roof last night. It apperas to be preety effecient because when the inside temp reached 500 degrees on the cure schedule the outside dome was only 108degs. How long does it take to get your oven up to cooking temp.....say 700-800 degrees?
I appreciate the insight because you can really go nuts and overthinking this project. You put so much work and dedication and pride into this project that the last thing you want is faliure. We wanted to have our first pie this Sunday but they are predicticling rain for this Sun so we may have to do Fri pizza.
G

[Neil2]

Re: curing, craks and vermiculite

"Is it safe to assume that the cracking on the outside is pretty typical and we should not worry."

Pretty typical and to be expected.

If you are worried about the final finish, you consider putting on third coat. Wait until after the final curing fire. The brick and oven will expand out with the heat, but upon cooling down will tend to leave the vermiculte layer in its "expanded" shape. A final coat at this point will cover small cracks and they will be less likely to reflect through.

[mrgweeto]

Re: curing, craks and vermiculite

Neil,
We pretty much realized that this is common. We saw this even before curing. We already poured our vermiclite in the cavity of the enclosure and are putting the plywood on the roof tonight. Didn't see any smoke or steam on any of the cures so we seem good to go.
Thank you,
G