Air Bubbles

Hi, The last time this happened to me, I was told it was overfiring that caused the "blisters" Regards Kevin.

Take a look at the info on bloating at

The short answer is 'yes'. First, though, are we talking about bloating rather than blistering as the explanation is different.

Hamer & Hamer describes bloating as "The unwanted blistering of the body (as distinct from the glaze) and is caused by trapped gases (as distinct from air bubbles in the raw clay). The defect occurs in stoneware and between body and slip in slipware. During firing, many gases are liberated from the body. Most of these escape through the body pores and if necessary through the molten glaze. If the body pores are blocked by a stiff fusion of body-glaze layer or by a tiff vitrifying slip, the gases cannot escape. They then build up pockets of gas behind a 'plastic' barrier which is distorted to accommodate the gas bubble."

It would be interesting to know if your work was slipware or stoneware. Hamer & Hamer goes on to elaborate on this problem and its correction according to which it is.

In article , Lindsay MacArthur writes

David, Lindsay asked whether airbubbles can develop _after_ the firing, she had already taken the pieces out of the kiln. I think the bubbles you refer to are happening during the firing, not once the pieces have cooled enough to be taken out, am i right? In which case the answer to her question is no, once a piece has cooled, it will not deform anymore.

Monika

-- Monika Schleidt snipped-for-privacy@schleidt.org