The Difference Between Overglaze and Underglaze Ceramic Tableware

Comparison of Production Techniques

1. Manufacturing Process

   • Underglaze: Patterns are painted on unglazed or bisque-fired ceramic bodies, then covered with a transparent glaze and fired at 1200-1400°C in a single high-temperature firing, fully fusing the pigments into the glaze.

   • Overglaze: Designs are painted onto an already glazed surface and fixed through a second firing at 600-900°C, leaving the pigments on the glaze's outer layer.

2. Firing Cycles & Temperature

   • Underglaze: Single high-temperature firing

   • Overglaze: Double firing (low-temperature second firing)

Physical Characteristics

1. Surface Texture

   • Underglaze: Smooth to the touch, with no raised patterns (fully embedded in the glaze).

   • Overglaze: Slightly raised designs, creating a tactile, textured surface.

2. Color Performance

   • Underglaze: Limited by high-temperature stability, pigments (e.g., cobalt/iron oxides) produce traditional hues like blue-and-white (qinghua) or copper-red (youlihong), with stable but narrower color ranges.

   • Overglaze: Low-temperature firing allows vibrant colors (e.g., sapphire blue, emerald green) and layered gradient effects.

3. Durability

   • Underglaze: Resistant to acid/alkali corrosion and thermal shock, lasting decades.

   • Overglaze: Prone to wear, fading, and accelerated corrosion when exposed to acidic foods.

Health & Safety Considerations

1. Heavy Metal Leaching Risks

   • Underglaze: Pigments are sealed under the glaze, posing no lead/cadmium leaching risks under normal use.

   • Overglaze: Low-temperature pigments may contain heavy metals; prolonged contact with acidic or hot foods increases leaching potential.

2. Purchasing Recommendations

   • Prioritize underglaze or lightly colored overglaze tableware.

   • Avoid frequently using overglaze dishes for hot soups, vinegar, or acidic foods.