Damn crack !

[Eastside3]

So after eons of planning, building, learning, and waiting between stages, I had finished the insulation and began the curing process. I should start by saying that i poured my hearth slab about 6 months ago, and the dome assembly was done about 4 months ago. Ive had the dome covered until it was time to insulate the outside. with 4 layers of 1" fiber blanket, plus extra around the chimney area, I then covered everything with lathe and put a generous amount of quickset mortar over it. This is destined to be a covered structure but I wanted the extra protection of a hard layer of stucco. I say this because when people talk about waiting before firing the oven, and when people talk about curing, there are lots of factors. In my case along time has passed between stages, so things are a bit different, and perhaps more forgiving, than for someone who is assembling an oven rather quickly. Well I THOUGHT I was doing things right.
After some small fires I proceeded to add a little bit of wood. you could say paper and splinters would be accurate. I fired it a few times a day, and then allowed larger pieces of wood to go into the oven. At the end of the week I had a large fire. The top of the domes internal temperature was 1100 degrees and the center of the floor was 850. I noticed two cracks running from front to back. The start near the center and spread out. They happen to be in the center of the two largest dome sections.
I dont know if these cracks are something to be alarmed about or not. Frankly there is nothing I can do about it at this point, but id like to hear from others who have cracks, and from other builders, and hear your thoughts based on the crack you see in the picture ive attached.

[mikku]

Re: Damn crack !

Hello Eastside3.
Cracks occurring are unavoidable. Your oven looks like a precast unit with a lot of pieces. The large cracks seem to line up with the sections. The refractory doesn't cure unless you do it with successive firings and still probably not totally because you cannot reach their design temperatures. Mines' also cast but only in three sections. It did not show any signs of cracking inside until it had been used several times for baking and pizza. Then some hairlines appeared that open and close as the oven goes through its use cycle. But they always close.
BTW, what do you cook at 1000 deg temperatures? Sounds like your just wasting firewood. Use it to cook anything and do pizzas taking 3 to 4 minutes instead of 90 seconds!--for a while! What is the hurry? But this is only my 2 cents--take it for what it is worth! cheers!