A 2024 Nature Research study (Zhang et al., npj Materials Degradation) shows that Han dynasty lead-glazed pottery carries a unique natural corrosion pattern that can only form after hundreds of years underground.
© The Metropolitan Museum of Art
1. Natural Mineral Layers
Over centuries, the glaze reacts with the soil and forms a complex mix of minerals:
Lead carbonate (PbCO₃)
Lead phosphate (Pb₃(PO₄)₂)
Calcium carbonate (CaCO₃)
Calcium phosphate (Ca₃(PO₄)₂)
These minerals develop extremely slowly as the glaze interacts with the surrounding soil. In many cases, ions such as Ca²⁺ and P⁵⁺ migrate through micro-cracks in the glaze and accumulate at the glaze–body interface, creating corrosion.
* Corrosion Model(Fig. 16 of this study)
© The Museum of Oriental Ceramics, Osaka
2. Iridescent Weathering (Rainbow-Like Surface Film)
Many authentic pieces show a thin, rainbow-like sheen on the glaze. This is caused by the long-term reaction between lead glaze, moisture, and soil salts. Artificial aging cannot reproduce the same optical effect or layered structure. (If corrosion has progressed extensively and the surface sheen has been lost, the iridescent effect may no longer be visible.)
* Irisdence Effect on Han Dynasty Green-Glazed (Examples from the Collection)
3. Microbial Traces in Glaze Cracks
This analysis shows organic materials and biofilm traces deep inside ancient glaze cracks. These form only when microorganisms live in the object for centuries underground. Modern reproductions do not have this biological signature.
a. Microbial Corrosion
b. Crack Corrosion
* Corrosion Model(Fig. 16 of this study)
4. A Distinct Multi-Stage Corrosion Process
Authentic Han lead glaze ages in a very specific way:
- Small pits appear on the surface
- Ions and microorganisms move into glaze cracks
- Phosphorus and calcium accumulate inside the glaze
The study demonstrates that the corrosion patterns found in Han dynasty lead-glazed pottery are products of long-term burial and cannot be artificially reproduced. These distinct chemical and biological signatures serve as reliable markers of authenticity.
What makes this study remarkable is that it scientifically validates what appraisers have long understood through intuition, while also confirming that the microbial activity previously assumed to exist is, in fact, real.
[Han Dynasty Green-Glazed Museum examples]
© Asian Art Museum San Francisco
© The Metropolitan Museum of Art
© Brooklyn Museum
© Asian Art Museum San Francisco
[Reference]
1.Zhang, K., Wu, C., Zhao, J., Yu, W. & Zhao, M.
The corrosion mechanism of lead-glazed pottery in Han dynasty.
npj Materials Degradation 8, 10 (2024). https://doi.org/10.1038/s41529-024-00428-y