What Should We Pay Attention to When Using Copper Oxide as a Ceramic Colorant?

1. Firing Atmosphere Control

Copper oxide exhibits completely different colors under different firing atmospheres. In an oxidizing atmosphere, the copper ion valence remains unchanged, remaining in its divalent state, resulting in a greenish appearance in the porcelain pattern. In a strongly reducing atmosphere, the divalent copper ions are reduced to monovalent copper ions and metallic copper colloidal particles, causing the pattern to turn red. Even slight variations in the intensity of the reducing atmosphere can significantly alter the color of the pattern. Therefore, ensuring a uniform and stable reducing atmosphere within the kiln is crucial for achieving a consistent red color.

2. Glaze Formula Optimization

Optimizing the glaze formula can improve the color stability of copper oxide. Research has shown that adding appropriate colorants and suspending agents to the glaze can effectively enhance color.

3. Cooling Process Management

The cooling process also significantly impacts the final coloration of copper oxide. Proper natural cooling time can prevent unnecessary glaze defects and ensure color stability and glaze texture.

4. Precise Temperature Control

Copper oxide is very sensitive to firing temperature. If the firing temperature is too high, the glaze will flow, and the copper ions will easily diffuse and volatilize, resulting in blurred patterns and a lighter color. If the firing temperature is too low, only a small amount of the copper oxide colorant will dissolve in the glass glaze. Even though the firing is also conducted in a strongly reducing atmosphere, the pattern will not appear vibrant red. Only when the firing temperature is perfectly adjusted and the atmosphere is relatively strong, can the copper-red pattern be formed, resulting in a pure, bright red color.

5. Raw Material Selection and Processing

The purity of copper oxide is crucial. High-purity copper oxide (CuO) should be used as a colorant. Modern technology has introduced nano-copper oxide, which has a small particle size and high activity, offering improved diffusion and color rendering. Using nano-copper oxide as a colorant can produce ceramic products with excellent color rendering, a lustrous glaze, a high yield rate, and excellent repeatability.

Mastering these key points can fully utilize the advantages of copper oxide in ceramic coloring and consistently produce high-quality ceramic products.

author: Hazel
date: 2025-09-12