Diagnostic Criteria for the Authentication of Imperial Qianlong Celadon Vases with Carved Underglaze Decoration

Prof. Nona Dronova, D.Sc. (Tech.)
ORCID: https://orcid.org/0009-0007-4867-9074

DOI of related works:

• https://doi.org/10.5281/zenodo.16738473

• https://doi.org/10.5281/zenodo.16794377

• 10.5281/zenodo.16919626

Abstract

This study presents a multi-level diagnostic analysis of an imperial Qianlong period (1736–1795) celadon vase with carved underglaze decoration. The vase demonstrates the classic features of high-quality Jingdezhen imperial production: globular form, twin handles, low-relief dragon motifs, and a transparent bluish celadon glaze. The research combines macroscopic stylistic examination, instrumental colorimetry, microscopic analysis of glaze microstructure, and comparative study with published museum and auction analogues. The diagnostic evidence confirms the authenticity of the object as a genuine imperial Qianlong porcelain.

Keywords:
Qianlong porcelain, celadon glaze, underglaze relief, Jingdezhen, microscopic diagnostics, Fe²⁺/Fe³⁺ balance, phase separation

1. Introduction

Celadon-glazed porcelain represented one of the most refined categories of Qing imperial wares. During the reign of the Qianlong emperor, Jingdezhen workshops produced celadons of exceptional quality, with subtle sky-blue tones and intricate carved motifs under a transparent glaze. The authentication of such pieces requires both stylistic and material analyses, supported by instrumental and microscopic data.

2. Object Description

• Catalogue number: QL-CLDN-VS-HND-001-RU

• Form: Globular vase with tall neck and twin scroll handles

• Height: ca. 40–42 cm

• Material: High-fired porcelain body

• Decoration: Carved dragons and clouds under transparent bluish celadon glaze

• Mark: Six-character Qianlong reign mark in seal script, underglaze blue

• Foot: Unglazed rim with firing traces and partial glaze overlap

3. Glaze Analysis

3.1 Visual Features

• Glaze tone: light bluish celadon with turquoise nuance, semi-transparent and glossy

• Surface: homogeneous, smooth, with high optical depth

• Glaze applied by dipping, consistent with imperial workshop technique

3.2 Instrumental Colorimetry

Using digital sampling and color conversion (RGB, HSV, CIELab), three vases were analyzed for comparative context:

Result: The studied vase (left) clearly belongs to the sky-blue celadon category (negative a* and b*, bluish hue, low saturation).

3.3 Coloration Mechanism

• Fe²⁺ dominance in reducing kiln atmosphere produces bluish tones; Fe³⁺ leads to green-yellow shift.

• Phase separation in the glaze matrix (Pb–Si–K domains) enhances optical scattering in the blue range.

• P₂O₅ addition stabilizes Fe²⁺, suppressing oxidation to Fe³⁺, thus maintaining the sky-blue hue.

• The balance of chemical and structural coloration defines the unique heavenly-blue (tianlan) celadon of Qianlong.

(Shi 2020; Li 2019; Jin 2021; Wang 2021).

4. Microscopic Diagnostics

Microscopic imaging of the glaze reveals:

• Fine crystalline inclusions (feldspar, quartz remnants), typical of high-temperature firing (>1250 °C).

• Phase-separated microdomains with different translucency, causing depth and optical scattering.

• Opalescent effect under angled light, confirming authentic structural coloration.

• Absence of artificial craquelure or staining, supporting authenticity.

These features match the microstructure described for imperial celadons in scientific studies (Li et al. 2019; Shi et al. 2020).

5. Base and Mark Characteristics

• Footrim: sandy tone, unglaized, with firing darkening on the outer edge.

• Mark: underglaze blue, six-character seal script "大清乾隆年製", evenly absorbed cobalt, sharp execution typical of imperial production.

6. Comparative Context

Analogues with similar form, glaze tone, and relief are preserved in:

• Palace Museum, Beijing (故宫博物院)

• National Palace Museum, Taipei

• Christie's and Sotheby's auctions, London/Hong Kong (USD 80,000–150,000 range)

7. Authentication Criteria

1. Glaze tone and microstructure: bluish hue, crystalline depth, phase separation.

2. Carved decoration: hand-carved underglaze relief, not molded.

3. Footrim: characteristic sandy tone, glaze overlap, firing traces.

4. Imperial reign mark: correct calligraphy, underglaze cobalt diffusion.

5. Comparative conformity: strong similarity to verified imperial pieces.

8. Conclusion

The vase demonstrates all diagnostic features of authentic Qianlong imperial celadon. The combination of stylistic, instrumental, and microscopic evidence supports its attribution to Jingdezhen official workshops.

References

• Shi, P. et al. Study on the coloring mechanism of the Ru celadon glaze from the Qingliangsi kiln site. Ceramics International 46 (2020): 14486–14494. DOI: 10.1016/j.ceramint.2020.06.139.

• Li, Y. et al. Revealing the coloration mechanism in the earliest Chinese celadon glaze. J. Eur. Ceram. Soc. 39 (2019): 1675–1683. DOI: 10.1016/j.jeurceramsoc.2018.10.007.

• Jin, X. et al. Celadon colour data association classification and its dynasty-kiln site characteristics. Ceramics International 47 (2021): 29567–29575. DOI: 10.1016/j.ceramint.2021.07.124.

• Wang, C. et al. Scientific study on the celadon glaze from the Donggou kiln. Nucl. Instrum. Methods Phys. Res. B 504 (2021): 100–108. DOI: 10.1016/j.nimb.2021.07.018.

• Kerr, R., & Wood, N. Science and Civilisation in China, Vol. 5, Part 12: Ceramic Technology. Cambridge University Press, 2004.

• Christie's. Important Chinese Ceramics and Works of Art. Hong Kong Sale Catalogue, 2022.

• Sotheby’s. Qing Dynasty Imperial Wares. London Sale Catalogue, 2021.