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Ceramics Glossary

Raku – generally refers to a type of low-firing process (1000 degrees c) inspired by traditional Japanese raku.  Western-style raku usually involves removing pottery from the kiln while glowing red hot & then placed into containers with combustible materials.  When the materials ignite the containers are closed.  Because it is a rapid process it puts the clay under great stress not only when the kiln is heated so quickly but especially when the glowing pots are removed and this can cause cracking and breakages as it cools.  It is a very dramatic and exciting process to watch and can create beautiful & rich colours which is why it is a process generally used for decorative rather than functional purposes.

Slipcasting –a ceramic forming technique for pottery and other ceramics, especially for shapes not easily made on the wheel.  A liquid clay body slip is poured into a plaster mould and allowed to form a layer, the cast, on the inside of the mould.  When the cast comes out of the mould it can be refined and altered by hand but it creates precise and consistent shapes.  This process is commonly used in mass produced pottery for continuity of shape and size.

Greenware – the term given to the ceramic piece before it has been fired.

Paperclay – sometimes referred to as fibreclay is any clay body that has had fibre (paper being the most common) added.  It makes the clay stronger, decreases warping, improves joining and gives the piece strength but lighter weight.  The paper burns off during the firing enabling the form to hold its shape.

Bisque or Biscuit firing – the name given to the first firing of pottery before it’s glazed.  Most pottery is bisque fired to 1000 degrees c  and the purpose of this firing is to convert greenware to a durable, semi-vitrified porous pot so it can be safely handled for glazing and decoration.

Stoneware – a term for pottery or other ceramics fired to a high temperature –typically between 1180-1280 degrees

Glaze Firing  - The ceramic piece is usually bisque fired and then glazed and fired (a variety of temperatures and techniques for example, raku, stoneware, earthenware, pit, bonfire etc).  The type of glaze used will depend on the type of firing as the ingredients used in glazes (& clays) are formulated to mature at certain temperatures.  Too high can cause it to deform or even melt, too low and it will not be durable. 

Grog - Grog is used in pottery to add a gritty, rustic texture.  It usually adds strength to pottery, reduces shrinkage and cracks, and adds texture.

Tru Vue - this is a museum glass which is used to glaze the frames.  It is a special anti-reflective glass and provides 99% UV protection as well as sealing the works from dust.


Oxfordshire, UK


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