Clay glossary

The description of a powder by specifying the percentage of material within a given size range or less than a specific size. Sieve mesh sizes are only an indication of maximum particle size.

A defect in glazed ware characterised by the engobe or glaze separating from the body in flakes. This is usually due to high compressive stresses in the layer.

A glaze or body fault resulting from trapped air erupting through the body or glaze during maturation in the kiln.

Fired or broken scrap pottery. Biscuit pitchers have various uses when crushed or ground, i.e. grog, fillers, stopping, etc.

The property which enables material to be deformed by a force which exceeds a certain minimum value and to retain its new shape when the deforming force is removed. The ability of a material to be modelled.

A fault caused by glazed parts of the ware being in contact with kiln furniture. Or over firing of a body and it "melts" onto the shelf.

This is a vitrified and translucent ware made from a body containing china clay, ball clay, quartz and feldspar, which is made traditionally and fired only once.

The amount of pore space in a ceramic material, which may consist of both open and sealed channels.

The mixing, blending, de-airing and extrusion of plastic clay bodies.

Small tall "pyramids", made from various ceramic materials, which fuse and bend over at given temperatures. Used in kilns to indicate accurate firing temperatures and heat work.