I finally got around to unloading a kiln I fired a few days after x-mass to clean out the glazed wares in shop-Its a small 12 cubic gas updraft.This is the longest I have ever let a kiln sit fired.Good thing we did not have an earthquake .
There where about 6 mugs that bloated on top shelve-I have not seen my Porcelain do this for many years
I tossed them all in trash and them pulled them out to show what bloating looks like -Its a bit hard to see in these small puny photos but it shows as bumps on the bottom
This is classic white clay body bloating-this clay is Laguna's Dave's Porcelain fires to cone 10-this spot got a lot of exit flue gases and the rest of kiln load was fine
The bubbles also come thru the glaze but its harder to see.Looks a lot like pimples on clay.