Introduction Working with Clay Pinch Pots Slab Building Coil Building Throwing Glazing Safety in the Pottery Gallery of Student's Work

Things to remember – About Glazing What is glaze? Pots are glazed for reasons of hygiene and decoration and in the case of earthenware, where the fired clay itself is porous, to hold liquids. Glaze is made up of at least three constituents: Glass Flux Stiffener Glass, usually in the form of silica, has a melting point of 1710°c so a flux is needed to bring down the melting point. Lead, sodium, potassium, calcium, magnesium, barium, lithium, boric and zinc oxide are all fluxes. The third constituent, the stiffener, is alumina. This is necessary to prevent the glaze running off the pot. To make the glazes more interesting, other ingredients are used for colour, opacity, texture and mattness. Developing a glaze is a precise business for many ingredients have more than one property. For example red iron oxide changed the colour of a glaze but also acts as a flux. Chromium oxide makes a glaze green, but also opaque and so on. Also be aware that glazes do not work in the same way as paint. For example mixing chromium oxide (green) with tin oxide (white) does not produce a pale green but a pink! It is also important that the glaze fits the pot during firing (clay and glaze both shrink during drying and firing so one has to match their shrinkages) Experimenting with glazes can be a very interesting and rewarding experience, but does take a lot of time and not a little research. Applying glaze Make sure the glaze is thoroughly mixed and sieved. You can dip, pour, paint or spray on a glaze You can double or triple dip with the same glaze or apply one glaze over another. Sponge, use resist (wax, latex or paper) Make sure the bottoms of all pots are wiped or waxed including a little way up the side in case of running. Leaving glaze on the bottoms will result in sticking to the kiln shelf ruining the pot and the shelf. Knock off any ‘blobs or drips’ of glaze Touch up ‘bald patches’ carefully with a brush Wash/wipe hands in between handling pots with different glazes to avoid contamination. Avoid spillage of one glaze into another which could ruin a glaze. Be aware that some glazes contain toxic ingredients and they all contain silica which is a hazard to health when dry. Do not eat, drink or smoke when glazing (or indeed in the pottery at all) and wash your hands afterwards.