States of clay
Glossary · Family 02 of 5
8 terms
States of clay
02 · States of clay
Plastic state
The stage at which clay holds enough water to deform without cracking. The ideal moment for modelling, throwing or building, since the material keeps the shape it is given while remaining flexible.
02 · States of clay
Leather hard
An intermediate state in which the clay has lost part of its moisture but can still be worked. It allows trimming, joining or decorating while the piece holds its shape more firmly than in the plastic state.
02 · States of clay
Bone dry
The stage at which the clay has lost all the physical water in its structure. The piece becomes extremely fragile and must be handled with care before it enters the kiln for the first firing.
02 · States of clay
Shrinkage
The reduction in size a piece undergoes during drying and firing. It is caused by water loss and structural changes in the minerals, and varies with the composition of the clay body.
02 · States of clay
Warping
Unintended deformation that appears during drying or firing due to uneven shrinkage within the piece. It can produce curves, twists or deviations from the intended form.
02 · States of clay
Chemically bound water
Water that forms part of the molecular structure of clay minerals. It is removed only during firing, at specific temperatures, producing irreversible changes that turn clay into ceramic.
02 · States of clay
Bisque
A piece that has been fired once and not yet glazed. Stronger than bone-dry clay and porous enough to absorb glaze, it is a fundamental stage of the ceramic process.
02 · States of clay
Point of no return
The moment in firing when chemical and physical changes become irreversible. From this point the material is no longer clay and takes on the permanent properties that make it ceramic.
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