Oxides, Art and Chemistry
Science and art are uniquely related, and chemistry is the science that makes almost every artistic process possible. From photography, to paint mixing, to choosing what paper to use, chemistry permeates art and makes it possible. Ceramic art depends almost entirely on the science of chemistry. It is the reactions of chemical components that create the vivid colors on pots and give clay its durability. Nevertheless, a degree in chemistry is not a prerequisite to creating beautiful ceramics.
One of the key chemical components in glazes are Oxides. The colouring oxides are transition metal oxides of vanadium, chromium, manganese, iron, cobalt, nickel and copper. Oxides are usually added to glazes in small quantities, less than 5 %. Some colouring oxides for example cobalt, copper and manganese act as a fluxes in the glaze and in large quantities will cause it to become runnier.
Glazes can be saturated with over 5 % of these colouring oxides, and the excess remains on the surface, often as a matt, metallic black. They do not however give any indication of their final color which only develops when fired under a glaze.
They often change colour after firing and the color depends on the type of base glaze and whether it is fired in oxidation or reduction. Transition metals can combine with different numbers of oxygen atoms to give different colours.
They are used in much the same ways as Underglaze colors. Applying a weak mixture of oxide and water onto a textured surface and then sponging off the surplus will leave a residue of oxide in the texture and often produces very attractive results under a transparent or white glaze.