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The Potter’s Dictionary of Materials and Techniques:
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Copper oxides 
This article of approximately 1060 words describes the use of copper oxides in glazes to produce a wide range of colours.
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Firing
This article has approximately 3360 words, with 8 diagrams. It covers the firing process, the stages, and the various types of firing.
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Maiolica
This article of approximately 1360 words includes 7 photographs and two recipes. There is a related colour chart on maiolica in the new colour section.
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Copper oxides
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 CuO and Cu2O (previously called cupric oxide and cuprous oxide). Both oxides are strong colouring oxides in glazes and give green to black and red-brown. In bodies the colour varies from fawn to green depending upon the amount of vitrification. Five per cent copper oxide in a slip is equivalent in colour to 2% in a glaze.
The metal copper occurs as native copper, but mostly it is combined with oxygen, carbon, sulfur and the metals lead, tin and zinc. There are over ten workable copper ores of which the oxide and carbonate ores are the most beautiful and also useful to the potter. See Copper ores.
Copper is used in electrical conductors, wires, terminals etc; as roofing; for pipes and boilers; and in the alloys brass, bronze, bell metal etc. These metals are easily oxidized before or during a firing. Metal filings will give strong speckle stains to bodies and glazes. Potters' merchants market the two copper oxides and copper carbonate.
Copper was the first metal to be worked by man. Copper was known in Egypt in 3000BC. Copper oxide was used in early glazes giving the turquoise of Egyptian faience, the green-blue of Islamic pottery and the greens of Chinese lead-glazed tombware, glazed Roman cups and of English medieval jugs.
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This article continues with the use of copper oxide in glazes and explains how the resulting colour can be green, blue, yellow, turquoise blue or pink according to the glaze constituents with which it is fused. Under the sub-heading COPPER OXIDE IN REDUCTION the creation of red-brown, purple-brown, yellow, bright red and metallic surfaces is thoroughly explained.
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Cross references:
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Copper ores
Metal release
Conversion factor
Recipe appendix
Colours
Reduction
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Colloid
Autoreduction
Striking in
Copper lustre
Raku
Colour plates
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Firing
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The process of conversion from clay to pot. It involves heat of at least 600°C (1112°F). Clay disintegrates in water but is changed by firing into a stone-like material, unaffected by water, and in some cases impervious to water. The change is called the ceramic change. Other changes occur during the firing, e.g. organic matter is burned away, the colour changes, a layer of glass is fused onto the surface.
The decorative effects which are used in pottery often require separate firings. The first firing converts the clay to pot. It is called the biscuit firing. Subsequent firings involve colour, perhaps underglaze colour, glaze, onglaze colour, lustre and are named after these purposes. They will vary in temperature, speed of temperature rise and fall, and in atmosphere (oxidation and reduction). However, it is often possible to achieve a number of results from one firing. It is only the sophistication of potting methods, occurring in the last 300 years, that has resulted in the general practice of separate firings for biscuit, glaze and colours. Prior to this, the general practice was a single firing, although the use of subsequent firings for different effects was known to early potters around the Mediterranean. See Biscuit, Through firing, Onglaze, Lustre, Oxidation and Reduction .
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The stages of biscuit firing are then described under:
Water smoking
Decomposition of vegetable matter
Ceramic change.
Burning out or oxidation of carbon and sulfur
Progressive vitrification
Cooling
The stages of glaze firing are described under:
Drying out
Start of glaze fusion
Continuation of vitrification of body
Integration of body and glaze
Cooling
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Cross references:
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Biscuit
Through firing
Onglaze
Lustre
Oxidation
Reduction
Drying
Water smoking
Water
Black core
Breakdown
Bloating
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Mullite
Cristobalite
Dunting: biscuit dunts
Bisc
Glost firing
Raw glazing
Ceramic change
Dunting: firing dunts
Fluxing action
Viscosity of molten glass
Glaze fit
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Maiolica
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Decorated tin-glazed earthenware. Maiolica was traditionally soft-fired with a lead glaze made opaque by tin oxide.
The low temperature, originally dictated by the type of clay and some of the colours used, was responsible for a delicate suffusion of colours which allowed strong colours to be used in a sensitive way.
Maiolicas originated in the Mediterranean where the warmer and drier climate made it possible to accept the porous body as practical. Good maiolica, wherever made, retains the relaxed spirit of the Mediterranean with its combination of richness and sensitivity, even though it may need to be made harder fired to be accepted as a practical ware.
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The article continues under HISTORY OF MAIOLICA and MAIOLICA METHODS with seven photographs.
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Cross references:
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Hispano-Moresque
Lambeth
Printing
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Nine colour plates
Recipe appendix
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Maiolica
Click the images for the full pages
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