Contemporary ceramic makers use clay to make a broad range of work that can be functional or sculptural. The practice of making ceramics encompasses a wide range of techniques which can be used individually or in combination. These include hand building techniques such as slab building, modelling and carving or wheel thrown work which can be manipulated on or off the wheel. Decoration is applied while the work is leather hard as slip, or after the first firing on or under the glaze.
Image: © Ella O'Connor
Ceramic Terms Explained
Slab building: rolled out flat pieces of clay which can be joined or placed in or over a mould.
Pinching: hollowing forms by hand.
Modelling: using hands and tools to add or take away clay.
Coiling: building up forms with coils of clay.
Carving: subtracting clay from a block of clay.
Throwing: making a pot on the wheel.
Turning: cutting away unwanted clay from a thrown pot.
Clay body: the name for the unworked clay in its raw state. Clays are mixed by suppliers to ensure consistency of plasticity ( workability) and firing temperature.
Earthenware clay: usually a red clay which can be fired to around 1100 degrees. To be fully waterproof earthenware needs to be glazed.
Stoneware clay: clay which matures at a higher temperature than earthenware but which becomes fused or fully waterproof without a complete glaze covering: usually fired to between 1150-1260 degrees.
Porcelain: fine white clay which when worked finely and fired sufficiently becomes translucent.
Leather hard: state of drying clay when it is hard enough to turn, carve or decorate without bending.
Slip decoration: slip is a thick solution of coloured clay which can be applied to a leather hard object by any of the techniques below.
Sgraffito: involving the cutting through a slip to reveal the colour of the clay beneath.
Slip trailing: using a special tool, a slip trailer, to flow lines and dots of slip over a surface, leaving a raised finish.
Marbling: mingling wet colours on a wet slip base.
Printing: applying patterns or texture with a sponge or chosen tool.
Transfer printing: decals can be bought or made, and are applied over dry slip or glaze.
Resist (non removable) Wax emulsion or paraffin wax burns away during firing.
Resist (removable) newspaper or latex laid over slip layer, then carefully removed.
Inlay: brushing slip into carved patterns on leather hard clay. When slip is leather hard, the excess is scraped back with a metal kidney. A softer version can be done when slip is wet, wiping excess slip off with a rubber kidney.
Glaze: a coat of glass forming coloured solution that must be fired to produce a water resistant surface. Glaze can be painted or sprayed on the work. brightly coloured 'brush on' glazes especially made for painting and for use in schools are widely available.
Dipping: a traditional method of glazing pots. first the inside is filled with glaze and is immediately emptied. The piece is then held by its base and is dipped rim first in the glaze, held for a few seconds, then withdrawn.
Metal Oxides: used to colour slips and glazes, are mixed with a clear or opaque white glaze. Mixed thinly they are used to paint over a white glaze, the technique of Maiolica.
Under glaze colours: ready mixed colours used in the same way, which are more stable.
Biscuit Firing: the first firing of a clay object so that it can take a glaze. The kiln temperature must rise very slowly to enable al moisture in the work to be expelled, and to prevent the work cracking, usually to 1050-1100 degrees centigrade.
Glaze Firing: the firing of the glaze onto an object, usually after it has been biscuit fired. the kiln temperature can rise more quickly but care must be taken to reach and maintain the right temperature for the glaze to mature.
Raw Glazing: the glaze is added to the leather hard pot and fired only once. This requires skill and is not usually done at school.
Oxidised Firing: a firing, as in a normal electric kiln, where glazes form with access to oxygen.
Reduction Firing: a method which excludes oxygen from the glaze surface changing the quality and colour of the glaze.
Raku Firing: is a form of firing where glazed pots made of strong clay are fired rapidly up to about 1000 degrees and removed from the kiln, plunged into a reducing medium such as saw dust, enabling the metallic qualities of the oxides used to colour the glaze to develop. An exciting process which enables students to see how glaze melts in the kiln and the effect of fifferent firing environments on glazes.