Base, Insulation, Dome, Flue, Curing.... CRACK CRACK CRACK

[umabatata]

So, I've built pizza oven and really appreciated these forums and the huge wealth of info that is on them. I got some old fire bricks for the dome, and some brand spanking new ones for the floor. Spent more than I could afford on good insulation and while my dad was up for a month we got stuck in and got to the stage where the dome is finished and the flue is up. No insulation on the dome yet - I thought I'd cure it and wait for our rainy late winter to finish, then insulate and do the final render in the summer.
So, let everything dry for almost 2 weeks, then started curing. I let my second curing fire get away a bit, and got a good crack - around the top of the dome, then out past the flue and onto the outer arch. I was gutted, but after looking through other peoples first crack experiences I calmed down and embraced it as character. Next fire it opened up and grew so I can see fire through it.... and now on the fourth fire it is a pretty significant network of cracks.
It is my intention to go all the way and crank up a full blown fire after a few more hot curing fires, but I am starting to get worried that the whole thing will fall apart. I had thought I'd grind out the cracks, and re-mortar them, but after 4 or 5 good hot fires. I'd love to hear from people who have had similar experiences
FYI - the interior cooking surface is 840mm diam. - I covered the outside of the brick dome with a layer of mortar to clean it up as the old bricks had corners missing etc and I wanted to be sure there were no sneaky air channels I had missed.

Thanks.

[david s]

You have a better chance of eliminating or reducing cracks in the dome if you do the curing with the dome insulation in place. It is the uneven expansion that causes the refractory great stress and it will be far greater when the outside of the bricks are cold and there's rapid water elimination, particularly from the top half of the dome. Never mind it's too late now, your oven will not fall down. You could try parging the outside of the dome with some more mortar, but the cracks are probably there to stay.

[umabatata]

that makes sense David. I'd read various opinions about whether curing before insulating or after was better and made the wrong call obviously. I'll grind out the cracks a bit, and remortar them, then leave it all for a while, then insulate, then re cure I think.

[gbiondo2]

Umabatata - What did you end up doing? I'm having a similar problem where I have a few big cracks in which I can see the fire through. See pic and video.. https://m.youtube.com/watch?v=bzgeUnxgppI