Editing Pottery (section)

====Atmosphere====
[[File:Bottle Kiln.JPG|thumb|A [[bottle kiln]]]]
The atmosphere within a kiln during firing can affect the appearance of the body and glaze. Key to this is the differing colours of the various oxides of iron, such as [[iron(III) oxide]] (also known as ferric oxide or Fe<sub>2</sub>O<sub>3</sub>) which is associated with brown-red colours, whilst [[iron(II) oxide]] (also known as ferrous oxide or FeO) is associated with much darker colours, including black. The oxygen concentration in the kiln influences the type, and relative proportions, of these iron oxides in fired the body and glaze: for example, where there is a lack of oxygen during firing the associated [[carbon monoxide]] (CO) will readily react with oxygen in Fe<sub>2</sub>O<sub>3</sub> in the raw materials and cause it to be reduced to FeO.<ref name="auto">'The Emergence Of Ceramic Technology And Its Evolution As Revealed With The Use Of Scientific Techniques.' Y. Maniatis. Mine to Microscope: Advances in the Study of Ancient. (ed. A.J. Shortland, I.C. Freestone and T. Rehren ) Oxbow Books, Oxford, (2009). Chapter 2.</ref><ref name="auto1">'The Firing Of Clay-Based Ceramics.' W. H. Holmes. Science Progress. Vol. 60, No. 237 (Spring 1972), pg. 98</ref>

An oxygen deficient condition, called a reducing atmosphere, is generated by preventing the complete combustion of the kiln fuel; this is achieved by deliberately restricting the supply of air or by supplying an excess of fuel.<ref name="auto"/><ref name="auto1"/>