Enhanced quality in stoneware glazes and pigments

Use of commercially prepared stains as a source of glaze and pigment colour leads to less individuality and subtlety. This thesis is about enhancing quality in stoneware glazes and pigments studying the effect of secondary fluxes fired in a reduction atmosphere. Emphasis is placed on establishing an accurate analysis of locally obtainable materials, which cumulatively form the main materials database utilized in this research, necessary in investigating the advantages of using actual analysis as opposed to theoretical analysis when performing glaze calculations. In order to carry out the numerous calculations associated with this research it is clear that the most logical way to do this was through the use of computer applications. This leads to the investigation of established software programs used for glaze calculation. Two main programs Insight™ (1986) and HyperGiaze™ (1988) have been reviewed, determining whether computer software glaze calculation programs assist in producing glazes which have a better fit, surface quality, and brightness of colour. Subsequently a glaze calculation program GLAZECALC has been written using a spreading sheet application incorporating the local materials database. This research has focused on traditional based stoneware glazes derivative of those originally used in the Song dynasty - 'Celadons and Chuns' and the Ming dynasty - 'Copper Reds', examining "flux substitution" as a means of enhancing the brightness of these glazes. It is noted that the incorporation of additional fluxes into a recipe as a colour enhancer, also has the effect in some cases of improving the surface quality of a glaze. As a consequence, considerable investigations have gone into researching Coefficient of Thermal Expansion, looking at a dual role in the substitution of fluxes i.e. colour enhancement and improved body fit. Recognising the importance of the purity of materials and the colour response to specific oxides, further investigations have been undertaken studying the interaction between secondary fluxes utilized in laminations for specific effects i.e. body, engobe/ slip, glaze and overglaze pigments. An exhibition of work is incorporated into this presentation, the subsequent pieces exhibited being vehicles on which the glaze research outcomes are illustrated