Technical notes

Paul Philp

CLAY

The clay used is a mixture of Devon ball clay, Staffordshire fire clay, and some earthenware clay. Various aggregates: sea sand and fire brick grog – crushed fire - bricks, are incorporated into the mix. 

MAKING

The pieces are all hand built – there is no mechanical process involved. The vessels are constructed with coils of clay or modelled with smaller, clay modules. Tree – bark, occasionally incorporated in the building process, is burnt away during firing leaving ‘fossil’ like impressions in the body of the work. At this ‘primary’ stage, the vessels are left ‘unfinished’ and are left to partially dry out before the later stages of the making. When nearly dry, various scrapers – saw blades, wooden tools, are used to refine and texture the surface. 

FIRING 

Two types of kiln are used – electric and gas. If combustible materials have been incorporated into the bodies of the pots –tree bark, then the gas kiln is used for the first  – ‘biscuit firing.’  This is because a gas kiln has a chimney that removes noxious fumes contained in the materials. The first firing is usually a long process, allowing gases and steam to escape slowly without any risk of rapid overheating and resulting explosions. The temperature of the first firing is about 1140C, taking a minimum of fifteen hours to reach this heat and another fifteen hours to cool. 

WHITE FINISH 

After the biscuit firing, a ‘slip’ – liquid clay – composed mainly of china clay, is brushed or dipped on the surface. The vessel is then fired a second time at 1140 C and repeated for a third time if an ‘opaque marble’ surface is required. The next stage the piece is dipped in a liquid ‘dry glaze’ mixture consisting of china clay and wood ash. It is in then left and when bone dry the surface is scraped until the glaze mixture is partially rubbed off. 

FINAL FIRING

The vessel is finally fired at the high temperature of 1245C. 

ENCRUSTED SURFACES

In order to achieve these many effects the process is long and experimental –results are unpredictable and not always successful. Materials or various mixtures of materials i e. wood ash, clay and ceramic colour, are brushed or smeared on with varying tools to create rough ‘unfinished’ surfaces. The intention is to create an ‘accidental’ natural weathered effect. The use of modified glazes of varying thickness, and colour are applied between as many as five or six separate firings. The intention is to finally produce a work that appears to have evolved naturally over the millennia: an object that harks back to the past but avoids being pastiche; an object that is contemporary but with a quality that is ‘timeless.’