[Mahootna]

I've been reading about cracking domes and have been wondering how porous cement is and whether any of this cracking might be the result of air expansion of air pockets between bricks that have been mortared over. Is the mortar sufficiently porous to allow the air to escape from such pockets as it heats during firing? If not, might that not be the source of some of these strange cracks that have been appearing?

I suppose one way to test the theory is to monitor how the cracks appear. If they appear as the oven heats up, but then close to some extent as the pressure equalises, air pockets might be the cause.

Of course, I cannot test the theory myself coz I am still in the planning stages. Would be nice to know whether small air pockets between bricks are dangerous to the dome, however, before I start building.

Cheers
Paul