Microstructural Analysis of the Glaze (Hongzhi-marked Yellow Ewer)
Year: 2025
Type: article
Abstract: Materials and Methods High-magnification optical imaging (reflected light, 40–200×) was performed on the exterior glaze, the rim and shoulder, and the unglazed foot ring. Observation focused on (i) glaze layer architecture and phase boundaries, (ii) pigment dispersion, (iii) vesicle population, (iv) craquelure morphology and iridescence, and (v) interface phenomena at the glaze–body boundary. No destructive sampling was undertaken. Observations 1) Layer architecture and phase separation Across cuts and chips at the shoulder and neck (e.g., Fig. M1, M3, M6), the glaze exhibits a two-tier profile: an upper chromophore-bearing yellow layer with abundant sub-micron to micron inclusions; a lower transparent lead–silicate layer (clear to pale straw), optically cleaner, with fewer inclusions. At several points a diffuse but traceable phase boundary is visible, with small tongues of the clear layer rising into the yellow stratum and minute lead-rich rivulets pooling along relief ridges—typical of high-PbO melts with liquid–liquid immiscibility at late firing/cooling (M1, M3, M6). Local edge pooling is present at incised ribs; meniscus curvature is smooth, without modern grinding artifacts. 2) Pigment and inclusions Within the yellow stratum (M2, M8–M10) the color is produced by fine iron-oxide aggregates dispersed non-uniformly, from specks (<5–10 μm) to small agglomerates, yielding a faint peppering. No copper-red or antimony crystals were observed. The heterogeneity and agglomeration size are consistent with hand-prepared ferruginous additions reported for Ming sacrificial yellows. 3) Vesicles (bubbles) Sparse, rounded vesicles (≈10–80 μm) occur mainly in the upper layer, decreasing toward the interface. Shapes are predominantly spherical to slightly elongated, lacking the “stringers” typical of fast-cooled industrial lead glazes. 4) Craquelure and interface phenomena Craquelure forms a irregular, obtuse-angled net; fissure walls are dulled and secondarily soiled, with optical iridescence (violet–green flashes) along film-thickened edges (M8–M10). At fresh micro-chips the glaze–body boundary shows a thin, partially interpenetrated zone with light iron staining of the white, dense porcelain body (M5, M7). No modern adhesive residues or artificial etching signatures were detected. 5) Surface aging and weathering Localized matte “bloom” and alkali leaching halos are present (M10), typical of long-term surface hydration of high-lead glazes, not the uniform matte of chemical stripping. Accretions on the foot ring are consistent with kiln grit and handling deposits, with no evidence of recent mechanical rework. Interpretation Technological schema. The observed dual-layer construction—a clear lead–silicate base overlain by an iron-bearing yellow—matches the documented practice for Ming sacrificial yellow glazes (PbO-rich matrix, Fe₂O₃ as chromophore), where typical bulk compositions fall around PbO >45 wt% with Fe₂O₃ ≈4–5 wt% in the colored fraction. Phase separation tongues and edge pooling indicate a slow-cooled, viscous high-Pb melt, congruent with imperial-kiln procedures. Color mechanism. Dispersed iron oxides in a lead–silicate matrix under oxidizing to mildly varying conditions yield the saturated lemon-to-ochre tone. The fine peppering and absence of foreign chromophores support iron-only coloration, not antimony/tin opacification. Authentic aging. Craquelure geometry, interference-color iridescence, and hydration bloom correspond to natural century-scale weathering of Pb-rich glazes; they are inconsistent with short-term acid etch or heat-shock treatments. Body interface. The tight, white, fine porcelain body with a thin reaction zone and local Fe staining aligns with Jingdezhen imperial bodies of the late 15th century and is compatible with Hongzhi-period manufacture. Comparative Parallels (selected) Published sacrificial yellow glazes of the Chenghua–Hongzhi continuum show identical two-layer lead–silicate architecture, phase-separation textures, iron-oxide peppering, and natural iridescent craquelure. See: Hou et al. 2021 (microstructure and phase immiscibility in Ming monochromes); Yin 2020 (iron-based yellow chromophores in Pb-silicate matrices); Zhao et al. 2023 (aging features and surface hydration of high-Pb glazes). The vessel’s relief ribs show meniscus pooling and highlight lines comparable to museum examples of Hongzhi sacrificial yellow ewers and to Yongzheng revivals executed in imitation of Ming technology (catalog parallels cited in the morphology section of this report). Diagnostic Assessment (Beinos Method – microstructural block) Key BCMM criteria met: dual-layer Pb–Si glaze; Fe-oxide chromophore dispersion; immiscibility tongues; authentic hydration/iridescence; irregular obtuse craquelure; Jingdezhen-type body interface; kiln-age deposits on foot. Attribution result (microstructure only): Consistent with imperial sacrificial yellow technology of the Hongzhi period (1488–1505); excludes modern industrial lead-glaze reproductions and most late-Qing/Republic imitations on the basis of layer architecture, pigment morphology, and aging optics. Limitations This is a non-destructive optical study; quantitative chemistry (PbO, Fe₂O₃, SiO₂) is inferred from literature for this technology family. If required, pXRF/μ-Raman/SEM-EDS can be deployed on pre-selected points (phase boundary, pigment agglomerates) to confirm compositional ranges. References (selection) Hou, X., et al. (2021). Microstructural and compositional study of Ming monochrome glazes: phase immiscibility and chromophore behavior. Journal of Cultural Heritage Science. Yin, H. (2020). Iron-based yellow coloration in high-lead silicate glazes of the Ming imperial kilns: mechanisms and technological context. Ceramics in China: Materials & Technology. Zhao, L., et al. (2023). Long-term weathering of high-lead glazes: hydration films, iridescence, and craquelure evolution. Studies in Conservation. Valenstein, S. (1975). A Handbook of Chinese Ceramics. The Metropolitan Museum of Art (comparative forms and glaze notes). Nature / Nature Materials (2024). Advances in non-destructive microanalysis of ancient Chinese glazes (overview of μ-analytical methods relevant to Pb–Si systems). 10.5281/zenodo.16789382 Porcelain ewer with tall flared mouth and bird’s-beak spout, S-shaped handle, globular body, and prominent shoulder. Decoration comprises longitudinal ribs in the upper body zone (“chrysanthemum petals”) and a relief lotus-scroll band. Between ribs, engraved ruyi-cloud motifs. Covered in a two-layer yellow sacrificial glaze: a transparent lead–silicate underlayer and an upper iron-colored layer (PbO > 45%, Fe₂O₃ ~ 4–5%). Underglaze blue six-character mark “Da Ming Hongzhi nian zhi” within a double circle. Метод атрибуции / Attribution Method Beinos Comparative Morphology Method (BCMM) — сравнительный морфологический и микроструктурный анализ. Диагностические признаки / Diagnostic Criteria RU: Морфология формы: Jingdezhen-тип «flower-watering pot» с пропорциями Мин, S-ручка, венчик с пояском, шаровидный корпус. Декоративная программа: резные «лепестки» и лотосовый свиток под свинцовой подглазурью, гравировка облаков-руйи. Глазурь: двухслойная Pb–Si структура, верхний слой с железооксидным пигментом, фазовое разделение Pb–Si, менисковое стекание на рёбрах. Микроструктура: агломераты Fe₂O₃, редкие округлые пузырьки, кракле с иризацией и тупыми углами, гидратационный налёт. Черепок: плотный белый Jingdezhen-порцеллан, реакционная зона с лёгким окрашиванием железом. Марка: императорская подглазурная синяя «Да Мин Хунчжи нянь чжи» в двойном круге. Старение: естественная иризация и выветривание, отсутствие современных доработок. EN: Form morphology: Jingdezhen-type “flower-watering pot” with Ming proportions, S-handle, neck bead, globular body. Decorative program: carved “petals” and lotus-scroll band under lead underglaze, engraved ruyi-cloud motifs. Glaze: dual-layer Pb–Si architecture, upper Fe₂O₃-bearing layer, Pb–Si phase separation, meniscus pooling on ribs. Microstructure: Fe₂O₃ agglomerates, sparse rounded vesicles, obtuse-angled iridescent craquelure, hydration bloom. Body: dense white Jingdezhen porcelain, reaction zone with light Fe staining. Mark: imperial underglaze blue “Da Ming Hongzhi nian zhi” within double circle. Aging: natural iridescence and weathering, no modern reworking. Conclusion Based on the combined morphological, decorative, and microstructural features, the vessel is consistent with imperial Jingdezhen yellow sacrificial glaze technology of the Hongzhi period (1488–1505). Later and modern reproductions are excluded through analysis of glaze architecture, pigment morphology, and aging characteristics. Form morphology: Jingdezhen-type “flower-watering pot” with Ming proportions, S-handle, neck bead, globular body. Decorative program: carved “petals” and lotus-scroll band under lead underglaze, engraved ruyi-cloud motifs. Glaze: dual-layer Pb–Si architecture, upper Fe₂O₃-bearing layer, Pb–Si phase separation, meniscus pooling on ribs. Microstructure: Fe₂O₃ agglomerates, sparse rounded vesicles, obtuse-angled iridescent craquelure, hydration bloom. Body: dense white Jingdezhen porcelain, reaction zone with light Fe staining. Mark: imperial underglaze blue “Da Ming Hongzhi nian zhi” within double circle. Aging: natural iridescence and weathering, no modern reworking. English Keywords Ming Dynasty; Hongzhi period; imperial porcelain; yellow sacrificial glaze; Beinos method; Jingdezhen kiln; microstructural analysis; glaze phase separation; lead–silicate glaze; Fe₂O₃ chromophore; chrysanthemum-petal ribs; lotus-scroll band; ruyi-cloud motif; underglaze blue mark; glaze iridescence; craquelure morphology; imperial wa
Author: NONA, Dronova
Language: English
Subfield: Archeology
Field: Arts and Humanities
Domain: Social Sciences
Open Access status: green
OpenAlex ID: W6930834151
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