Hairline cracks inside cob oven

[mtra0001]

Hi guys, I cured my brand new cob oven for the past 6 days. Today I decided to try and burn off the black carbon inside my dome but noticed some long hairline cracks running inside the dome as shown in the enclosed images. I decided to hold fire as I wasn’t sure whether further increasing the temperature would create further issues. Do you believe there is cause for concern?

[david s]

You don’t say how long you left your oven to dry between completing it and the first fire. But, as a rule of thumb, depending on air temperature, movement and humidity, it takes around a week per inch of thickness to dry sculptural clay work and a cob oven much the same. Even when dry the firing must proceed slowly or cracking and at worst steam spalling result.

[mtra0001]

I let it dry out for almost 3 weeks. I suspect the last fire was a bit on edge and led to most of these cracks. Like I said they are very narrow cracks and will probably try to patch them up after I clean out the black carbon.