UGR-06008     Jar with underglaze-red decoration of incised

                            peacock and peony

Yuan dynasty, Hu-tian Kiln, unmarked.
Height: 30.1cm, Mouth diameter: 21.5cm, Foot diameter: 19.7cm, Interior foot diameter: 0.7cm     Weight:5955g
This ware has been cleansed with Oxalic Acid to remove dirt and viscidities to restore its original luster for collection and preservation.

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Erect neck, extended shoulder, slender belly, and flat bottom. These are standard descriptions of a vessel in Yuan dynasty.

 This ware was joined on the belly. Using acicular tools, diamond shapes were engraved around the neck whereas peacocks, peony sprays and plantain foliage were engraved on the body. Copper red pigment was painted on blank areas and coated with a layer of white glaze.  

Copper oxide used as pigment was fired with glaze coating together under reductive flame. Copper elements are easily volatilized and dissociated under high temperature, so it is rare to find pure underglaze-red porcelains.  

The glittering surface glaze appears light green.

Peony with its rich colors and radiance has been given the honor as the king of flowers. It is a common decorative element found in company with lions, phoenixes, and peacocks. Since late Yuan dynasty, wider peony leaves are gradually adopted by artists.  

After combustion, chap lines on the glaze surface are formed as a natural reaction accounted for the difference in surface tension of clay and glaze.

Metallic oxides are used as pigments for both underglaze-blue and red porcelains. These pigments, however, consisted of different metallic elements.  

Cobalt oxide used for underglaze-blue produces solid coloration, and has a wider range of firing temperature. On the other hand, copper used for underglaze-red is much more unstable than cobalt.  

Minor inconsistencies with the firing temperature, pigment blend, or ingredients in the glaze can alter its manifestation on the finished porcelains. For instance, blackish red can be attributed to excessive copper content while lower firing temperature or too much copper loss during the firing process may result in gray. For this reason, pure red underglaze is extremely rare.

In Yuan dynasty, binary formula reinvents the clay required for porcelain production. By mixing general clay with high alumina Ma-chang clay, the new formula proves to withstand higher firing temperature and stabilize ware formation under high temperature. However, the alumina contents also reduced the clays plasticity. Hence, most larger wares in Yuan dynasty are formed by combining separately shaped parts.  

Porcelains from Yuan dynasty share the following common features: large figure, thick clay, heavy ware, hard quality, white color, and sectioned bonding.

The bottom of jar is unglazed with a heart-shaped kneading lump at center. The uneven surface is flintlike red with black iron spots.

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Copper red pigment volatiles and dissociates easily under high temperature. Brush works diffuses easily. Green or yellow spots occur periodically.

 Large and small air bubbles scatter evenly on the surface.

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Clay in Yuan dynasty was mixed according to binary formula. The grayish white color, loose and rough structure with obvious air holes indicates a less refined quality. Sand holes, brush marks, and iron spots are found on the bottom of ware.

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