|Monthly Tech-Tip |
When clay materials and bodies bubble as they melt or over fire. This normally happens in raw materials that contain particulates that produce gases during firing.
Key phrases linking here: bloating, bloated, bloat - Learn more
Bloating is a fault that can occur in the firing of glazed or unglazed porcelains, stonewares and earthenware clay bodies. Large or small bubbles/blisters on the surface indicate a firing rate or temperature that the body or material cannot tolerate. Please find more detail in the Trouble Shooting section.
Electric Hobby Kilns: What You Need to Know
Electric hobby kilns are certainly not up to the quality and capability of small industrial electric kilns, being aware of the limitations and keeping them in good repair is very important.
Warping happens during the firing of ceramic ware when there is a high degree of vitrification and inadequate measures are taken during forming and firing to prevent it. Unexpected warping often happens with unstable shapes and over firing.
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.
A common fault in reduction gas fired ceramic ware made from iron bearing clays. The interior cross section of the clay turns black.
Laminations because of improper pugging of a clay body will cause separations and drying cracks in the ware.
To potters, stonewares are simply high temperature, non-white bodies fired to sufficient density to make functional ware that is strong and durable.
Bloating occurs when the off-gassing of decomposing particles in a body has not completed by the onset of density and impermeability associated with the vitrification process.
|By Tony Hansen|
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