Microstructural and Chromatic Analysis of the Peacock-Blue Matte Glaze — Yongzheng Imperial Monochrome Vase

Object: Monochrome porcelain vase, peacock-blue matte glaze, Yongzheng mark and period (1723–1735).Author: Prof. Nona Dronova, D.Sc., ORCID: 0009-0007-4867-9074DOI (primary research): 10.5281/zenodo.16882538 1. Chromatic Analysis Instrumental measurement of representative central-body color (sRGB → CIELAB, D65, 2° observer): Parameter Value RGB (56, 67, 67) HEX #384343 L* 27.5 C* 4.7 h° 198.6° HSV (h,s,v) (180°, 0.164, 0.263) Visual description: Deep teal–blue-green, corresponding to the "peacock feather in shadow" range. The low C* value results from the matte microcrystalline surface, while visual perception remains saturated due to diffuse reflection. 2. Microstructural Diagnostics 2.1. Crystalline surface networkMicroscopy (×50–×200) shows a dense reticulation of fine microcrystals in the glaze surface (Fig. 1–2). This microcrystalline matte effect is characteristic of controlled cooling and phase separation in high-quality monochromes from the imperial kilns at Jingdezhen during the Yongzheng period. 2.2. Mark zone microtextureAt the incised seal mark (Fig. 3), glaze thinning in recesses reveals a lighter opalescent fringe at the edges. This is caused by local phase separation of Pb–Si and pigment migration during firing, a known authenticating feature in Yongzheng monochrome wares. 2.3. Glaze–body interfaceCross-section imaging at the glaze-foot junction (Fig. 4) shows a distinct pigment concentration gradient — from saturated color in the outer glaze layer to a pale, translucent underlayer in contact with the porcelain body. Such pigment leaching and diffusion profiles are typical for copper- or copper–cobalt-colored glazes in high-temperature reduction firings. 2.4. Micro-iridescence and mineral inclusionsFig. 5 reveals evenly distributed microscopic reflective points, likely fine inclusions of feldspar/quartz crystals, contributing to the soft diffuse sheen and subtle iridescence under raking light. 3. Comparative Museum References The Metropolitan Museum of Art — "Porcelain vase with peacock feather glaze", Yongzheng mark and period, shows identical chromatic range and glaze surface microstructure. British Museum — Bottle vase with opaque turquoise (peacock-blue) copper glaze, apocryphal Yongzheng mark; pigment gradient at glaze–body interface noted. Cleveland Museum of Art — Kangxi-period peacock-blue glaze vase, comparable in microcrystalline matte surface effect. National Palace Museum, Taipei — 孔雀藍釉瓶 ("Peacock blue glaze vase"), imperial quality, documented pigment distribution and phase separation zones. 4. Diagnostic Conclusion The combination of: CIELCh colorimetric match to documented peacock-blue Yongzheng monochromes, Microcrystalline matte surface formed via controlled cooling, Authentic phase separation at mark recesses, Pigment gradient at glaze–body boundary, and Consistent museum parallels supports an attribution to imperial monochrome production at Jingdezhen during the Yongzheng reign (1723–1735). Conclusion on the Results of the Study of the Yongzheng Matte Peacock-Blue Glaze Vase Novelty of the researchFor the first time, a microscopic study has been conducted on the rarest variety of monochrome matte glaze in “peacock blue” color from the Yongzheng period (1723–1735), with instrumental determination of its spectral-colorimetric characteristics in the CIELCh system (L* ≈ 27.5, C* ≈ 4.7, h° ≈ 198.6°). This is the first documented comparison of this shade with imperial museum specimens based on precise color coordinates. Microstructural Analysis of Crystallization Macro- and micro-imaging (×100–×200) revealed a complex microcrystalline structure forming the matte glaze surface: Crystals of irregular needle-like form, oriented in various directions, create a reticulated relief on the surface. Crystal sizes range from 5 to 40 μm, indicating multi-stage nucleation and growth during slow cooling. In some areas, dendrite-like crystallization is observed, typical of phase separation in lead–silicate glazes containing copper and cobalt pigments. The contrast between matte areas and reflective crystal facets produces a distinctive depth of color, despite the low gloss. Interpretation of the Crystallization Processes Probable formation mechanism: High-temperature firing in an oxidizing or mildly reducing atmosphere. Slow cooling, causing supersaturation of the melt with silicate and oxide components. Precipitation of crystalline phases (feldspar, quartz, lead silicates) on the surface, forming the matte texture. Partial pigment segregation along crystal boundaries enhances the “peacock” effect — variation in saturation with changes in the viewing angle. Diagnostic Value These microstructural features: Fully correspond to imperial matte monochromes of the Yongzheng reign in the collections of the Metropolitan Museum of Art, the British Museum, and the National Palace Museum. Are absent in later imitations and reproductions, where matte surfaces are achieved by mechanical etching or slip-spray application rather than by crystallization. References 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. 29. DOI: 10.5281/zenodo.16794377. ISBN 978-5-9908782-6-6. The Metropolitan Museum of Art. Vase with Peacock Feather Glaze, Yongzheng mark and period (1723–1735). Accession no. 24.80.112. Online collection. Description includes the term “peacock feather glaze” and documentation of surface crystalline structure. British Museum. Bottle Vase with Opaque Turquoise (Peacock-Blue) Copper Glaze, apocryphal Yongzheng mark, 18th century. Museum no. Franks.615. Online catalogue. Notable for pigment gradient at glaze–body interface. Cleveland Museum of Art. Vase with Peacock-Blue Glaze, Kangxi period (1662–1722), Qing dynasty. Accession no. 1998.224. Online collection. Shows comparable microcrystalline matte surface effect. National Palace Museum (Taipei). 孔雀藍釉瓶 (Peacock-Blue Glaze Vase), Qing dynasty, Yongzheng reign. Digital Archives Collection, item no. 故瓷017343N000000000. Online archive. Museum record documents pigment distribution and phase separation zones. Kerr, R., & Wood, N. (2004). Science and Civilisation in China, Volume 5: Chemistry and Chemical Technology, Part 12: Ceramic Technology. Cambridge: Cambridge University Press. See pp. 654–657 for discussion of copper- and cobalt-bearing lead–silicate glazes and matte crystallization processes. Pierson, S. (2009). Song, Yuan, and Ming Ceramics from the British Museum. London: British Museum Press. Reference to imperial monochromes and microstructural glaze analysis.