Underglazes are a great way to colour your pots. Using this method they can be completed at different stages- either when the pot is still unfired or after the first firing. Under glazes are available in a massive range of colours from all the top suppliers like like Maco, Bath potters, Potclays, Potterycrafts, CTM and nearer to Potterydayz is Corby Kilns. You just simply paint them on in a couple of coatings and leave to dry. Once they have been fired a clear glaze can be applied to the surface. the two feather pots featured use blue and red underglaze and can be purchased form the store on this site.
A slip is a liquid clay that has been coloured using a variety of materials like body stains and oxides. They are used normally at the leather hard stage on a pot in a variety of processes. Pouring, dipping, spraying trailing and brushing are the most common. Slips can be made by adding colours to a white liquid clay
or sometimes by combining clays with the for- mentioned additions of oxides and stains. This method of decoration is used with both earthenware and stoneware but traditionally more at earthenware as seen in my own examples here.
These are elements which are combined with oxygen. Iron is a good example which when combined is called iron oxide. Other examples include cobalt, copper, magnesium, zinc, lead, calcium, sodium, barium, potassium, calcium, strontium,antimony, lithium and boric oxide.
Oxides can be used mainly in a two ways: firstly they can be simply sponged, washed or brushed onto the body of a pot, usually after firing in order to affect the glazed surface during firing.
Glazes can be bought from a manufacturer already prepared to suit your needs or they can be created from individual ingredients much like a recipe. The ingredients of a glaze are largely divided into three areas, specifically fluxes, silica and alumina. Many materials are used as fluxes in glazes to lower the melting point of the glaze- of which oxides play a large part. Silicas, which form glass are commonly found as flint or quartz but are also naturally combined with other materials such as China clay, which also contains alumina. Alumina is the ingredient in a glaze that sticks the other materials to the pot in firing. There is an enormous range of types of glazes with multiple colours achieved and textures. The small jug above uses copper and cobalt oxide under a clear glaze fired to stoneware temperatures.