Overglaze decoration (釉上彩)

Overglaze decoration, known as You Shang Cai (釉上彩) in Chinese, is a traditional ceramic decoration technique where colored designs are applied to the surface of a previously fired and glazed ceramic object. After the decoration is applied, the piece is fired again at a lower temperature (around 700-900°C) to fix the colors without melting the glaze. Overglaze decoration allows for a wide range of vibrant colors and intricate patterns, making it a popular technique for fine ceramics, especially in Chinese porcelain.

Overglaze decoration contrasts with underglaze techniques, where the decoration is applied before glazing and high-temperature firing. Overglaze is especially valued for its ability to produce more detailed and vivid designs, as well as its adaptability to a wide range of artistic styles.

Key Steps in Overglaze Decoration:

1. Initial Firing (初次烧制): The ceramic piece is first shaped and fired at a high temperature (above 1200°C) with a layer of clear or translucent glaze.
2. Application of Overglaze (釉上彩绘): After the first firing, artists apply the overglaze decoration, often using a variety of colors and pigments that do not interact with the underlying glaze.
3. Second Firing (低温烧制): The decorated piece is fired at a lower temperature (700-900°C), which allows the overglaze colors to set and fuse to the surface without melting the glaze underneath.
4. Detailing (修饰): After firing, additional hand-painting or gilding may be added to enhance the design.

Challenges in Overglaze Decoration:

1. Color Fading During Firing:

   • One of the major challenges in overglaze decoration is that some pigments can fade or change during the second firing. While underglaze techniques allow colors to be fired at high temperatures, overglaze pigments must withstand lower temperatures without losing vibrancy. Maintaining the intended color requires precise control over firing temperatures and pigment selection.

2. Firing Precision:

   • The second, lower-temperature firing process is delicate. The temperature must be carefully controlled, as too much heat can cause the colors to blur or fade, while insufficient heat may prevent the colors from properly adhering to the surface. Achieving the perfect balance is a technical challenge for artisans.

3. Fragility of Overglaze:

   • Overglaze decorations are more prone to wear and damage compared to underglaze designs. Since the decoration is applied on top of the glaze, it is more exposed to the elements and everyday handling, which can cause the colors to fade or scratch over time. Extra care must be taken in the use and preservation of overglaze ceramics, especially for functional items like dishes or teapots.

4. Complexity in Design:

   • The precision required for applying intricate patterns is much higher with overglaze techniques, as the artist is painting on a smooth, slippery surface. Mistakes in overglaze painting can be harder to correct because the colors are applied after the initial glazing and firing. The need for accuracy in brushwork and design makes this process labor-intensive and demanding of artistic skill.

5. Material Limitations:

   • Not all colors and pigments can be used in overglaze techniques because some pigments may not react well to the lower firing temperature. This limits the palette available to artists, and finding the right combination of pigments that will maintain their intended hue and consistency during firing can be challenging.

6. High Production Costs:

   • Overglaze decoration typically requires two separate firings, adding to the production time and cost. The need for highly skilled artisans to paint the intricate designs, combined with the risk of color changes or defects during the second firing, increases both labor and material costs. This makes high-quality overglaze ceramics more expensive to produce.

Conclusion:

Overglaze decoration (You Shang Cai) is a highly skilled and complex craft that allows for vibrant and intricate ceramic designs. However, the challenges of maintaining color consistency, controlling the second firing, and preserving the fragile surface make it a demanding technique. Despite these difficulties, overglaze decoration remains an essential and admired part of traditional and modern ceramic artistry, producing some of the most ornate and detailed porcelain pieces in Chinese art.