Cracking from the first curing fire

[Wirenut]

I am building an oven, and came to the curing phase. During the first curing fire of about 200 - 250 degrees F the dome cracked on the side from the bottom row of fire brick to about 2/3 way up. The crack is about 1 - 2 mm wide (on the outside) when I did the second curing fire at about 250 - 300 degrees F.

The question is:

What is an acceptable crack in the dome if any?
Do I need to do any type of repair to the crack?

Any advise would be welcome!

Wirenut

[Sixto]

First a caveat, I've not done my drying fires yet, so I don't know what cracks I may get in a week or two, or if I can live with them.

From what I've read so far, all domes have cracks, it just depends on whether you can live with them or not. A photo of your oven would help guide responses. I'm guessing if you can see the 2mm crack on the outside the dome is not insulated yet. So if that's the case, (depending on whether the cracks are through mortar or bricks) and you really want to fix it, it may not be too hard to remove the affected bricks or mortar joints without disturbing the surrounding bricks, clean affected surfaces, re-wet them and re-pack with fresh refractory mortar. Best-case scenario would-be when the crack is at a mortar joint, and you can grind out the mortar and pack the gap with fresh mortar. (unlikely if your crack is as long as 2/3 of the dome height.)

Another option if the dome is not yet insulated, is to stop the curing/drying fires use a high-temp sealant (something that can stand 1000 degrees or more) to fill the crack from the outside while you continue to insulate and render the dome as-it-is, and hope the crack doesn't get any bigger, or leak smoke through the insulation when you resume your drying/curing fires. Remember, insulation helps the bricks and mortar share the heat load so they are subjected to less thermal shock.

Finally, The acceptability of any of these options is completely up to you, and may have no impact to the useability of your oven. I'm keeping my fingers crossed for both of us.

[MarkJerling]

I am building an oven, and came to the curing phase. During the first curing fire of about 200 - 250 degrees F the dome cracked on the side from the bottom row of fire brick to about 2/3 way up. The crack is about 1 - 2 mm wide (on the outside) when I did the second curing fire at about 250 - 300 degrees F.

The question is:

What is an acceptable crack in the dome if any?
Do I need to do any type of repair to the crack?

Any advise would be welcome!

Wirenut

Remember that if you insulate before starting your curing fires, you have a better chance to avoid cracks. Uninsulated ovens crack far more easily.

But, there are two types of ovens: Those with cracks and those who's owners say they don't have cracks. So, a minor crack will not be a problem.

[Pizzarotic]

What is an acceptable crack in the dome if any?
Do I need to do any type of repair to the crack?

Is this a brick or cast oven?