Jingdezhen overglaze polychrome porcelain, known as wucai (literally “five colors”), is a type of overglaze decoration that gradually developed during the Ming and Qing dynasties. The materials and techniques of wucai can be traced back to lead green glazes of the Han dynasty, the tri-colored glazed wares of the Tang dynasty (Tang sancai), as well as the liuli glaze and fahua polychrome decoration of the Yuan dynasty.
The technical difference between colored glazes and wucai mainly lies in whether the ceramic body is covered with glaze and the corresponding firing temperatures. Low-temperature overglaze decoration can be traced back to the red-and-green polychrome wares of the Jin dynasty (Fig. 1), which were primarily produced in the northern Cizhou kiln system. These had a significant influence on the red-and-green polychrome wares of Jingdezhen during the Yuan dynasty.
After the Ming dynasty began, wucai, which was still in its nascent stage, largely continued to appear in the form of red-and-green polychrome within both official and civilian kiln systems for a considerable period. From the perspective of the development of ceramic craftsmanship, it is reasonable to include these red-and-green wares within the broader definition of Ming and Qing wucai from Jingdezhen. More narrowly defined, however, wucai often refers to the type of overglaze decoration that emerged in the mid-to-late 15th century, characterized by black pigment outlines filled in with various colors and then fired (Fig. 2). Whether broadly or narrowly defined, both forms are important parts of wucai’s evolution and together represent one of the most original and significant overglaze polychrome porcelain styles in the history of Jingdezhen ceramics.
A simple analysis of the material principles behind wucai may help to clarify its technical features by offering a more direct understanding through its material compostion.
Wucai is a type of low-temperature glassy material primarily composed of lead and silica, with a firing temperature ranging between 800°C and 900°C in an oxidizing atmosphere. The basic colors included in wucai are red, yellow, green, blue, purple, and black. The first pigment to understand is fanhong (alum red) or iron-red, which is a red pigment derived from qingfan (green vitriol). The main chemical component of qingfan is ferrous sulfate (FeSO₄). The production of fanhong involves calcining qingfan to transform it into ferric oxide (Fe₂O₃), a reddish substance. This is then repeatedly washed to remove impurities and coarse iron particles, resulting in a fine ferric oxide powder. This powder is then ground and mixed in a ratio of approximately six parts lead powder to one part iron powder.
One notable chemical characteristic of fanhong is that when mixed with other pigments, it tends to turn yellow after firing. The reason for this is that when fanhong comes into contact with the lead-based glass frit used as a base glaze in other pigments, it reacts and transforms into a colorant that shifts in hue. For example, when green is applied over fanhong, it turns yellow; the combination of green over yellow results in a light green. Similarly, purple over fanhong yields a brown color. Therefore, to preserve its red hue, fanhong is usually applied separately in wucai decoration and is rarely mixed with other pigments.
The black pigment used in wucai is also known as shengliao, or “raw material,” in contrast to shuliao (“processed material”). Shengliao refers to uncalcined, unfused natural mineral soil or synthetically prepared mineral compounds. For example, during the mid-Ming period, a mineral pigment known as Pingdengqing - a raw material mined in Leping, Jiangxi - was commonly used. In the Qing dynasty, typical overglaze black pigments included Zheliao from Jinhua, Zhejiang, and Zhumingliao from Yunnan. All of these are representative raw mineral materials used for black pigments in overglaze decoration during the Ming and Qing dynasties.
The ideal raw material for overglaze decoration is a cobalt-rich mineral ore with a high manganese and low iron content. This is because only a high manganese content can produce a purple to black hue within a lead-based glaze. The exact color that emerges depends on the percentage of the pigment in the glaze and the degree of fusion during firing. For instance, when raw material is directly used to paint outlines, the pigment particles form a relatively thick and raised layer. Upon firing, they fuse with the overlying colored glaze and produce a purplish-black hue - essentially a black appearance - due to the high concentration of colorants in the overglaze pigment. This effect is what gives us the characteristic black outlines seen in wucai decoration. When the raw material is used instead as a colorant, it is mixed in smaller proportions into lead glaze, and the resulting color is the manganese purple commonly seen in wucai ware.
Aside from fanhong (alum red) and shengliao (raw black pigment), the other pigments used in wucai are composed of two main components: a base glaze and a colorant. The base glaze primarily consists of silica (SiO₂) and lead oxide (PbO). In practice, the ratio between these two components can be adjusted to control the thermal expansion properties of the pigment during firing. For instance, if a pigment contains insufficient silica, it may develop surface cracks or even peel off after firing. Conversely, if there is too much silica, the surface may become uneven, or the glaze may turn cloudy and lose its translucency. Therefore, maintaining a proper balance between silica and lead in the glaze mixture is crucial.
The main metallic colorants used in wucai are iron, copper, cobalt, and manganese. In a lead-based glaze, these metals produce the following colors, respectively: yellow (iron), green (copper), blue (cobalt), and purple (manganese). In practice, these pigments can be blended - by mixing two or more independently prepared colors - to create additional variations. Thus, the color diversity found in wucai is essentially the result of combining different metal oxides within the same base glaze.
The development of wucai during the Ming dynasty can be seen as a gradual expansion of the color palette. Over more than two hundred years of evolution, the range of wucai pigments became increasingly complete, reaching full maturity by the late Ming period. The reigns of Tianqi and Chongzhen marked the golden age of wucai, during which it fully matured both technically and artistically.
As the late Ming dynasty faced collapse, the imperial kiln complex at Jingdezhen - directly controlled by the court - was largely inactive. In contrast, civilian kilns flourished due to high demand in both domestic and export markets.
Surviving official kilns wares from the Tianqi and Chongzhen periods are extremely rare. Aside from a few pieces of blue-and-white porcelain, no wucai wares have yet been definitively identified from the official kilns of this era. However, two dated pieces preserved in public collections stand out as crucial artifacts for the study of wucai during this period. One is a “blue-and-white wucai lidded jar with entwined lotus scrolls,” inscribed “Made by the Tang family, 3rd year of Tianqi,” now in the Gotoh Museum in Japan (Figs. 3-1, 3-2). The other is a “wucai dragon dish,” inscribed “For use in the Zhao residence, spring of the jiaxu year,” corresponding to the 7th year of Chongzhen, housed in the Musée Guimet in France (Fig. 4).
The Tianqi wucai lidded jar, both in craftsmanship and painting technique, reflects the standards of late Ming official kiln production. Its decorative style retains echoes of the Jiajing and Wanli periods, but the technical execution surpasses comparable Wanli-era works.
The Chongzhen wucai dragon dish, dated to the 7th year of the Chongzhen reign, is one of approximately six known surviving examples. These are housed in the Percival David Foundation (UK), the Musée Guimet (France), the Palace Museum in Beijing, the Shanghai Museum, and private collections. A blue-and-white dragon dish with the same inscription also exists. This wucai dish features a central design of a dragon among clouds, a border of ocean waves and rocks along the inner rim, and two pearl-chasing dragons on the outer wall. The decoration uses five color pigments - purple, yellow, green, turquoise, and red - resulting in a finely crafted and mature example of late Ming wucai.
The Chongzhen wucai dragon dish, with its precise dating, provides an important benchmark for the materials and techniques of wucai during the Chongzhen period. It also offers a rare glimpse into quasi-official kiln production of the time. Dated wucai artifacts from the Chongzhen era are extremely rare; one notable example is a fragment in a Hong Kong antiques dealer’s collection, bearing a standard script mark in fanhong reading “Made in the 2nd year of Chongzhen, Great Ming.”
To be continued ...
This blog article series is based on a paper written by Mr. Li Yanxun of the Yanshan Art Museum in Jingdezhen for the 2018 special exhibition Eastern Brilliance: Special Exhibition of Japanese-Commissioned Porcelain from Late Ming China, organized by the Tang Ying Society. The paper was published in the exhibition catalogue released in 2021.