[gjbingham]

Robert,
It's only evident when the dome is heated. I was firing the thing up and "pow". I'm thinking that it was just firewood sounding funny, but 45 minutes later, I notice that one of the bricks has a crack right through it from an extension of one of the existing dome cracks that seal up when the oven cools down. Check out Dusty's photos. It looks just the same. The crack runs down a mortar joint, back and forth between bricks then, bam, right across the middle of one in the second or third row (I forget which).