Underglaze
An archaeological excavation at the Tongguan kiln Site proved that the technology of underglaze colour arose in the Tang and Five Dynasties periods and originated from Tonguan, Changsha.
[7] This produces the effect of highlighting and lending spectral variance to relief patterns that are embossed into pieces such as tableware such as bowls or jars.
Underglaze in Ptolemaic faience was widely used for Ushabti dolls en masse for grave goods in the late Kingdom period.
[11] This cobalt had a tendency to run when used in a tin glaze, and Persian artisans relied on the experimentation of the Chinese in Jingdezhen porcelain to achieve clear blue designs in their ceramics.
Due to the Middle Eastern demand for blue and white porcelain the primary use of this underglaze technology was utilised in creating many designs with Islamic decoration.
[13] Persian pottery, which was aware of Chinese styles throughout the period, made great use of underglaze decoration, but mostly in a single colour, often blue using the local cobalt, but also black.
A copper printing plate engraved with the design would transfer underglaze pigment to a piece of dampened tissue paper through a rolled press which could then be adhered to earthenware.
[19] Low firing temperature underglazes have been formulated as well as application options such as in the form of liquid pens of glaze or solid chalk blocks.
The application of underglaze techniques such as stained slips have diversified and a variety of artists have created independent chemical processes of their own to achieve desired effects.
Within commercial production there is a decline in underglaze use in comparison to 18th century use due to the creation and improvement of other glazing techniques that do not require such a high heat point.
A well-known New York underglaze tile and pottery decorator of the 1940s, Carol Janeway (1913-1989), was diagnosed with lead poisoning after eight years of using a lead-based overglaze, retiring in 1950.
Counterfeiting operations have developed both in foreign areas and within China[22] to profit from the collectability of Ming and Qing dynasty blue and white porcelain.
From the baroque period onward, there was a slight decline in the profitability of forging Chinese porcelain as European hard paste techniques were developed but kept as industry secrets in countries such as Germany and France.
In the last three decades there has been a considerable increase in demand for antiques of Ming and Qing porcelain amongst China's rising middle class, which has led to another growth in counterfeiting efforts to supply the large amount of new collectors.
