Oct 22, 2026: We are working on protecting our servers against the PHP2Shell vulnerability recently discovered. Servers were upgraded ahead of schedule on Oct 21. This could cause some issues. Please contact us if you encounter any.
Bloating in a high iron raw clay ground to 42 mesh (Plainsman M2). It is still stable, dense and apparently strong at cone 4 (having 1.1% porosity). But at cone 6 (top bar) it is bloating badly. At cone 5 the clay experiences the early stages of bloating. Cone 4 is thus "dangerous territory" for this particular clay. A reminder of this can be seen by putting on a transparent glaze - it fills with clouds of micro-bubbles from off-gassing that has begun well below cone 4.
| Troubles |
Over Firing of Ceramic Glazes and Bodies
Overfiring can happen with glaze, engobes or clay bodies. The problem is more subtle than you might think. |
| Troubles |
Bloating
Bloating occurs when the off-gassing of decomposing particles in a body has not been completed by the onset of density and impermeability associated with vitrification or overfiring. |
| Glossary |
Clay Body Porosity
In ceramics, porosity is considered an indication of density, and therefore strength and durability. Porosity is measured by the weight increase when boiled in water. |
| Glossary |
Vitrification
A process that happens in a kiln, the heat and atmosphere mature and develop the clay body until it reaches a density sufficient to impart the level of strength and durability required for the intended purpose. Most often this state is reached near zero p |
| Glossary |
Terra Cotta
A type of red firing pottery. Terra cotta clay is available almost everywhere, it is fired at low temperatures. But quality is deceptively difficult to achieve. |
![]() PayPal | No tracking, No ads, No paywall, No transient content! Just organized, concise information constantly updated and improved. Was this helpful? Consider supporting me. |
Buy me a coffee and we can talk