Chromium oxide is an inorganic compound with green crystals. Its chemical formula is Cr2O3. In nature, it occurs as chromite. This substance is mainly used as a pigment for wear-resistant materials, abrasives, and ceramic glazes. It is also widely used in smelting metal chromium and dye manufacturing.
Qing Shunzhi eggplant skin purple glaze dark engraved cloud and dragon pattern plate (Collected by the Palace Museum)
Traditional ceramic glazes are made by firing minerals such as quartz, feldspar, kaolin, etc. Glaze color mainly depends on the metal oxides contained in the minerals used. As a special metal oxide, chromium oxide is gradually favored by the ceramic industry because of its unique green color and good coloring stability.
Adding chromium oxide to ceramic glazes can give ceramic products a unique green color. This green glaze can be applied to various ceramic vessels, decorations and other products. Moreover, the concentration of chromium oxide in the glaze can be adjusted so that the ceramic surface appears in different shades of green, giving ceramic products richer artistic expression.
In addition to color, chromium oxide also lowers the firing temperature and improves the melting performance in ceramic glazes. This undoubtedly reduces energy consumption and improves production efficiency for ceramic products.
It is worth mentioning that the application of chromium oxide in ceramic glazes can also achieve a magical effect called "color-changing glaze." This color-changing glaze is achieved by doping chromium oxide and other metal oxides in the ceramic glaze, such as cobalt oxide, iron oxide, etc. During the firing process, chromium oxide interacts with other metal oxides, generating a series of complex chemical reactions. This results in a breathtaking, rich, layered color effect on the ceramic surface.
Color-glazed porcelain is a major category of Chinese ceramics. Its rich colors and crystal-clear aesthetic features have won people's favor. Precious color-glazed porcelain is also famous for its "light," "color," "transparent," and "clean" properties. People fall. Starting from the high-temperature celadon glaze that began to appear in the Xia Dynasty, the firing of Chinese color-glazed ceramics has a history of more than 4,000 years. Black glaze appeared in the Han Dynasty, celadon-white glaze and Jun kiln color glaze were popular in the Song Dynasty, and Kangxi, Yongzheng, and Qianlong in the Qing Dynasty. Its development was unprecedented during this period, with sophisticated firing technology and dozens of glaze colors. Pieces of colorful glazed porcelain are like dazzling artificial gemstones, colorfully decorating the Chinese ceramic garden.
Jun kiln rose purple glazed rectangular flowerpot from the Song Dynasty (Collected by the Palace Museum)
White is warm; red is rich; yellow is bright; green is calm; purple is elegant; and black is solemn. Different colors of glazed porcelain reflect the different aesthetic tastes of the Chinese people. In this regard, Lu Chenglong, chief expert of the Artifacts Department of the Palace Museum and director of the Ceramics Research Institute, explained: "For single-color glazes, uniformity, and purity are the basic requirements for people's aesthetics; kiln-varnished glazes give people an abstract and hazy beauty. Again Craftsmanship defects and defects such as flakes and spots can also make ordinary glaze colors produce interesting diversity and evocative."
Colored glazed porcelain is made by mixing metal oxides and natural ores as colorants into the glaze, which is applied to the porcelain body and fired. Ceramic color glaze can produce color mainly due to the selective absorption and scattering of light by the glaze layer. According to Lu Chenglong, before the Kangxi Dynasty of the Qing Dynasty, the colored metal elements in my country's traditional color glazes, such as celadon glaze, black glaze, blue glaze, high-temperature red glaze, green glaze, yellow glaze, purple glaze, sauce glaze, and tea powder glaze mainly include Iron, copper, cobalt, manganese, magnesium, etc. Starting from the Kangxi Dynasty, with the introduction of European painting enamel materials, kiln workers gradually mastered the coloring mechanism of antimony, gold, and other metal elements. They created egg yolk glaze (also known as light yellow glaze, lemon yellow glaze, foreign glaze). Famous glazes include yellow glaze, antimony yellow glaze etc.), and gold-red glaze (including rouge purple, rouge water, light pink, etc.).
Ming Cui Green Glaze Jar (Collected by the National Museum of China)
If distinguished by firing temperature, color-glazed porcelain is divided into three types: high, medium, and low. Wang Jing, director of the Social Education Department of the China Ceramics Museum in Jingdezhen, introduced that high-temperature colored glazes use calcium oxide as a combustion accelerant, apply various colored glazes on the blank, and then fire them at a temperature above 1250°C, such as white glaze, Bright red glaze, blue glaze, etc.; low-temperature colored glaze uses lead oxide as a combustion accelerant and is fired into a plain body at a low temperature. The plain body is then covered with colored glaze and fired at a kiln temperature of 700°C to 900°C. Carmine red, delicate yellow glaze, light yellow glaze, brother green glaze, etc., belong to the second firing; medium-temperature glaze is the color glaze between high-temperature glaze, and low-temperature glaze, such as malachite green, felt wrapped green, etc. Also, It belongs to secondary firing.
"In addition to the formula of the glaze, the firing temperature and the atmosphere in the kiln also have an indirect impact on the color of the glaze." Lu Chenglong said that a glaze containing an appropriate amount of copper oxide can be fired in an oxidizing flame. Green, but can be burned into red in the reduction flame; there are also Ge kiln porcelain glaze colors in the Song Dynasty, including green, gray, pink, green, fried beige, etc. Although the glaze formula is the same, because the utensils are placed in different positions in the kiln, the temperatures felt are inconsistent and different colors are produced. Therefore, finding two pieces of color-glazed porcelain with the same color is almost impossible.
