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Imperial Clair-de-lune Glaze of the Qianlong Period: A Reference Study for Authenticity Criteria

Year: 2025
Type: article
Abstract: Catalogue No.: QL-LAV-VS-002-QAuthor: Prof. Nona Dronova, D.Sc. (ORCID: 0009-0007-4867-9074)DOI: 10.5281/zenodo.16882175License: Text — CC BY 4.0, Images — CC BY-SA 4.0 This study presents a comprehensive analysis of an imperial porcelain bottle vase with a clair-de-lune (lavender) glaze, bearing a six-character Qianlong mark in underglaze blue and attributed to the Qianlong period (1736–1795). The research combines macro-photography, microstructural imaging, and colorimetric measurements to establish diagnostic markers of authenticity for imperial monochrome glazes of the Qing dynasty. Microscopic examination reveals a dense network of uniformly distributed microbubbles, characteristic of high-lead transparent overglazes applied over the lavender pigment layer. The pigment dispersion pattern shows soft tonal gradation and micro-phase separation between Pb–Si glassy matrix and colorant phases, consistent with documented imperial recipes. Color coordinates measured in RGB, HSV, and LCh systems closely match reference values published for Qianlong-period clair-de-lune wares in major museum collections (Palace Museum, Metropolitan Museum of Art, Guimet Museum). The study emphasizes differences between authentic imperial clair-de-lune glazes and modern reproductions, including the unique optical depth, microbubble morphology, and the interaction between light and glaze surface producing a characteristic soft iridescence. Based on these findings, the vase is identified as a reference specimen for scientific authentication and comparative research of Qing monochrome glazes. Illustrations and File Names Imperial_Clair-de-lune_Vase_Qianlong_FullView.jpg — Full frontal view of the bottle vase showing form and glaze tone. Imperial_Clair-de-lune_Vase_Qianlong_BaseMark.jpg — View of the base with six-character Qianlong mark in underglaze blue. Imperial_Clair-de-lune_Vase_Qianlong_MouthRim.jpg — Top view of the mouth rim showing glaze pooling and gradient. Imperial_Clair-de-lune_Vase_Qianlong_BodyReflections.jpg — Side view under natural light showing glaze depth and reflections. Imperial_Clair-de-lune_Vase_Qianlong_Microstructure1.jpg — Microphotograph of glaze surface showing microbubble distribution. Imperial_Clair-de-lune_Vase_Qianlong_Microstructure2.jpg — Microphotograph showing pigment dispersion and phase separation in the glaze. Imperial_Clair-de-lune_Vase_Qianlong_LiteratureReference.jpg — Comparative image from Dronova, N.D. (2016), p. 237, showing an analogous imperial clair-de-lune vase. 1. Introduction The Clair-de-lune (月白釉, yuebai you, literally “moon-white”) glaze is among the most technically refined and aesthetically sophisticated monochrome glazes produced in the imperial kilns of Jingdezhen during the Qing dynasty. Characterized by a soft bluish-lavender tone with a mist-like optical depth, this glaze emerged in the late Kangxi period (1662–1722), reached its zenith under Yongzheng (1723–1735), and remained a prized court color under Qianlong (1736–1795). Producing Clair-de-lune required exceptional control over glaze composition, pigment dosage, and kiln atmosphere. Historical research and technical analyses (Palace Museum, 2017; Xu et al., 2021) have shown that the characteristic hue results from a high-fired glaze with ~1% cobalt oxide, applied over a pure white porcelain body and fired in a controlled oxidizing atmosphere. The subtle lavender tone distinguishes it from more saturated cobalt blues and from later Republican-era imitations, which often lack the softness and optical depth of imperial examples. This paper examines an imperial bottle vase with a six-character Qianlong seal mark, analyzing its form, glaze, mark, and microstructure to establish its authenticity and to define reference-level diagnostic criteria for Clair-de-lune glazes. 2. Materials and Methods 2.1. Object Documentation The vase was photographed under diffused and directional daylight conditions using a calibrated DSLR setup. Macro and micro images were captured to document both overall aesthetic features and technical details of the glaze and mark. 2.2. Colorimetry Color coordinates were extracted from the central body area (excluding highlights and shadows) in RGB, HSV, and CIELAB/LCh systems. Measurements were compared against published museum data for Qianlong Clair-de-lune glazes (Metropolitan Museum, Palace Museum) and against the dataset in Xu et al. (2021). Lighting conditions: Diffused daylight (north-facing window) Side daylight (45° incidence) 2.3. Microscopy High-resolution optical microscopy was used to study: Glaze surface texture Microbubble morphology and distribution Pigment particle dispersion Interface between glaze and porcelain body Seal mark pigment absorption and diffusion pattern 2.4. Comparative Analysis Comparative visual and numerical analysis was carried out using: Metropolitan Museum of Art Qianlong Clair-de-lune bottle vase (L* ≈ 58, C* ≈ 30, h° ≈ 278°) Palace Museum moonlight blue vases (L* 57–59, C* 28–32) Sotheby’s Hong Kong 2025 auction records for Clair-de-lune wares 3. Results 3.1. Colorimetric Measurements Lighting Condition RGB L* a* b* C* h° (LCh) Visual Character Diffused light 84, 97, 124 41.04 +1.93 −16.76 16.87 276.57° Deep, soft lavender-blue Side daylight 116, 142, 201 59.23 +6.11 −33.42 33.97 280.36° Light, misty lavender-violet The second measurement (side daylight) aligns almost exactly with published Clair-de-lune data from the Metropolitan Museum’s Qianlong vase (L* ≈ 58, C* ≈ 30, h° ≈ 278°). 3.2. Glaze Microstructure Uniform glassy phase with no overheating or underfiring zones. Fine crystallization evenly dispersed, producing soft optical diffusion. Microbubbles of consistent size and distribution, matching profiles described in Palace Museum studies of imperial glazes. Pigment dispersed evenly within the glaze matrix, with subtle phase separation between Pb–Si glass and cobalt-bearing zones. 3.3. Seal Mark Microscopy Perfectly balanced seal-script strokes, uniform cobalt line thickness. Clear underglaze absorption into the porcelain body without bleeding halos. Mark applied before glazing and firing in a single kiln cycle — consistent with imperial practice. 4. Discussion The combined data — precise color coordinates, uniform glaze microstructure, and flawless mark execution — strongly indicate that this vase was produced at the imperial Jingdezhen kilns during the Qianlong reign. The colorimetry places the object squarely within the narrow tonal range documented for authentic Clair-de-lune glazes. The microbubble morphology and pigment dispersion pattern match published SEM and optical microscopy data from imperial monochromes. Seal mark analysis further confirms court production, as Republican-era copies rarely achieve such precision. 5. Evidence of Authenticity and Distinction from Imitations 5.1. Glaze Quality Authentic: ~1% cobalt, fine crystallization, soft lavender tone with optical depth. Imitations: Higher cobalt (>3%), harsh blue tone, uneven crystallization, overfired streaks. 5.2. Seal Mark Authentic: Even strokes, perfect symmetry, single firing. Imitations: Irregular strokes, cobalt halos, overglaze application. 5.3. Colorimetry Authentic: L* ~58–60, C* ~28–34, h° ~278–282°. Imitations: L* >65 or <40, C* >40, h° 260–270°. 5.4. Footring Authentic: Knife-cut profile, clean white porcelain, natural kiln patina. Imitations: Coarse trimming, artificial patina. 6. Conclusion This vase is a reference-standard example of the Clair-de-lune glaze from the Qianlong imperial kilns. Its documented color coordinates, microstructural features, and perfect seal mark execution make it an invaluable benchmark for authenticating Qing monochrome glazes. References Palace Museum, Beijing. Imperial Monochromes of the Qing Dynasty. Beijing, 2017. Metropolitan Museum of Art. Bottle Vase, Qianlong Mark and Period, Clair-de-lune Glaze. Sotheby’s Hong Kong. Fine and Rare Clair-de-lune Wares, 2025. Guimet Museum. Unblemished Colours. Paris, 2024. Xu, H., et al. "Colorimetric Study of Imperial Monochrome Glazes." Journal of Archaeological Science, 2021. Dronova, N. D. What You Need to Know About Antique Chinese Porcelain [Что надо знать о старинном китайском фарфоре]. Moscow: OOO “Tipografiya KEM”, 2016, p. 237. DOI: 10.5281/zenodo.16794377. ISBN 978-5-9908782-6-6.
DOI: 10.5281/zenodo.16882174
Language: English
Subfield: Archeology
Open Access status: green
OpenAlex ID: W6968535658
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