A fine red-glazed saucer dish,  Yongzheng six-character mark and of the period. Photo courtesy Bonhams

The curved body flaring outwards rising from a short recessed circular foot, the exterior evenly applied with a layer of deep crimson red glaze, the base with a six-character Imperial kaishu mark in underglaze-blue within double circles. 14.9cm diam. Estimate HK$ 

The rich red derived from copper oxide was first used at Jingdezhen in the fourteenth century as an underglaze pigment, usually mixed with iron oxide to give the rich maroon coloured glaze. By the Qing dynasty however, the colourant was composed of copper-lime mix without the presence of iron, hence it was considered one of the most difficult underglazed pigments to fire, due to the volatility of copper causing over-firing and wastage. As firing of the underglazed copper red pigments requires temperatures in excess of one thousand two hundred and fifty degrees Celsius, but can only be consistently controlled by using wood-burning kilns, the ceramic wares cost three to four times more than other porcelain fired during this period. 

Copper red monochromes are generally fired in a reducing atmosphere, where the richness of the colour is greatly enchanced bu a short period of re-oxidation during the end of the firing cycle. This process is tiresome and often misfired, as a slight miscalculation in time and technique will result in the copper glaze turning green. 

Compare a similar but slightly larger red-glazed dish with Yongzheng six-character mark and white fishes motif, in the Palace Museum, Beijing, illustrated inMonochrome Porcelain. The Complete Collection of the Treasures of the Palace Museum, Shanghai, 1999, p.28, no.25. See also another similar dish with a rare six-character Yongzheng mark within double squares in underglaze-blue (accession no.24.80.286), bequeathed by Mary Clark Thompson to the Metropolitan Museum of Art, New York, illustrated by Suzanne G. Valenstein, A Handbook of Chinese Ceramics, Boston, 1975, p.221, no.157. 

Bonhams. FINE CHINESE CERAMICS AND WORKS OF ART. Hong Kong. 24 Nov 2013 14:00 CST