Iron-Rich Hare's-Fur Glaze on a Song-Dynasty Jian Tea Bowl: Comparative Portable X-Ray Fluorescence Analysis of Brown and Black Glaze Regions and the Ceramic Body

Nona DronovaIndependent Researcher2026 Research Article | Chinese Ceramic Archaeometry | Glaze Technology Abstract This paper presents a comparative archaeometric investigation of a Chinese Jian-type tea bowl of the Song dynasty, characterized by a distinctive iron-rich hare’s-fur (tuhao, 兔毫) glaze. The vessel exhibits a warm brown exterior, a dark interior, and fine blue-black to greenish-black radial streaks extending from the central well toward the upper walls. Three regions of the bowl were examined by portable X-ray fluorescence spectroscopy (pXRF): the brown glaze, the black glaze, and the unglazed ceramic base. The measurements recorded elemental iron concentrations of 4.134 wt%, 3.692 wt%, and 3.166 wt%, respectively. The corresponding theoretical Fe₂O₃ equivalents are 5.91 wt%, 5.28 wt%, and 4.53 wt%. The brown glaze is enriched in iron relative to the black glaze, while the black glaze contains more silicon. Calcium is strongly concentrated in the glazed regions, reaching 4.180–4.319 wt%, compared with only 0.220 wt% in the unglazed ceramic body. These results are compared with published compositional and microstructural investigations of historical Jian hare’s-fur glazes. Particularly significant is the correspondence with research demonstrating iron enrichment in brown-yellow streaks and relatively higher silicon concentrations in adjacent black glaze. The combined elemental and photographic evidence provides a detailed characterization of the bowl’s iron-rich glaze system and contributes original comparative data to the study of Chinese high-fired tea ceramics. Keywords: Jian ware; Song dynasty; Tenmoku; hare’s-fur glaze; tuhao; iron-rich glaze; tea bowl; pXRF; Fe₂O₃; calcium-rich glaze; ceramic archaeometry; Chinese ceramics. 1. Introduction The black-glazed tea bowls produced at the Jian kilns in Fujian Province occupy a prominent position in the history of Chinese ceramic technology and tea culture. During the Song dynasty (960–1279), Jian tea bowls became especially valued for their dark glazes, which provided a visual contrast to the pale foam produced during contemporary methods of tea preparation. Among the most celebrated Jian glaze effects is hare’s fur (tuhao, 兔毫), characterized by fine, elongated streaks extending down the glazed interior of the vessel. The appearance of these streaks results from complex high-temperature processes involving iron-rich glaze compositions, melt movement, phase separation, and crystallization during firing and cooling. Modern archaeometric investigations have identified iron-oxide crystalline phases, including ε-Fe₂O₃, in historical Jian glazes. These studies demonstrate that the distinctive appearance of hare’s-fur decoration reflects sophisticated interactions among glaze chemistry, firing atmosphere, and cooling behavior. The present paper examines a Song-dynasty Jian tea bowl with a characteristic radial hare’s-fur pattern. The investigation combines three portable X-ray fluorescence measurements with photographic documentation of the vessel’s glaze and ceramic body. The primary objective is to compare the elemental compositions of the brown glaze, black glaze, and unglazed base and to place the resulting data within the established scientific literature on Jian ceramic technology. 2. Description of the Investigated Tea Bowl The investigated object is a Chinese Jian-type tea bowl associated with the Song-dynasty tradition of iron-rich black-glazed stoneware. The bowl has a broad, gently flaring profile, a slightly everted rim, and a comparatively small circular foot. Its exterior is covered with a warm reddish-brown glaze that becomes progressively darker toward the lower body. Near the foot, the glaze develops a deep blue-black coloration, while the lowest portion of the foot remains unglazed. The interior displays a striking radial pattern. Fine dark blue-black and greenish-black streaks extend outward and upward from the central well across a warm brown glaze background. The streaks vary in width, length, and density, producing the characteristic visual effect traditionally described as hare’s fur. The central well contains a dark, glossy glaze accumulation. Photographic enlargement reveals numerous small, rounded dark features distributed within the glaze. These characteristics provide the visual and morphological context for the elemental analysis. 3. Materials and Methods 3.1. Portable X-Ray Fluorescence Analysis The elemental composition of the bowl was examined by portable X-ray fluorescence spectroscopy. The analytical measurements were performed on 28 October 2026 using an instrument with serial number 940487. The analytical settings were recorded as Geochem (3-Beam) Extra, with an acquisition time of 45 seconds per measurement. The investigated vessel was designated Sample No. 6. Three consecutive measurements were performed: Measurement No. 10: Brown glaze (tarelka korich). Measurement No. 11: Black glaze (tarelka cher). Measurement No. 12: Unglazed ceramic base (tarelka niz). These measurements were selected to characterize the chemical differences between the two glazed regions and the exposed ceramic body. 3.2. Optical Documentation Four photographic images were used to document the bowl: Enlarged view of the radial hare’s-fur pattern. Enlarged view of the glaze surface showing rounded dark features. Overall view of the interior and radial decoration. Side view showing the vessel profile, exterior glaze, and unglazed foot. The photographs provide direct visual evidence of the bowl’s glaze distribution, decorative pattern, and surface morphology. 3.3. Elemental-to-Oxide Conversion For comparison with published ceramic compositions, selected elemental concentrations were converted into theoretical oxide equivalents using conventional stoichiometric factors. The following conversion factors were applied: Fe × 1.4297 = Fe₂O₃ equivalent. Si × 2.1393 = SiO₂ equivalent. Al × 1.8895 = Al₂O₃ equivalent. Ca × 1.3992 = CaO equivalent. K × 1.2046 = K₂O equivalent. These conversions express the measured elemental concentrations in a conventional ceramic-oxide format. 4. Experimental Results 4.1. Elemental Composition of the Three Regions Table 1. Comparative pXRF measurements of the Song-dynasty Jian tea bowl (Sample No. 6) Element Brown glaze, No. 10 Black glaze, No. 11 Unglazed base, No. 12 Si (wt%) 30.14 34.31 25.08 Al (wt%) 7.89 8.10 12.66 K (wt%) 3.899 4.360 2.922 Ca (wt%) 4.180 4.319 0.220 Fe (wt%) 4.134 3.692 3.166 Ti (ppm) 3030 3010 3250 Mn (ppm) 311 268 238 Co (ppm) 212 193 147 Cu (ppm) 64 72 89 Zn (ppm) 96 97 57 As (ppm) 24 20 ND, <10 Pb (ppm) 47 47 72 S (ppm) 3710 3840 5060 Source: Original portable X-ray fluorescence analytical report, instrument No. 940487, 28 October 2026, Sample No. 6, measurements 10–12. ND denotes a value below the reported detection threshold. 4.2. Iron Distribution Iron is a major compositional feature of all three investigated regions. The brown glaze contains 4.134 wt% Fe, the black glaze contains 3.692 wt% Fe, and the unglazed ceramic base contains 3.166 wt% Fe. The brown glaze therefore contains approximately 12.0% more elemental iron than the black glaze, relative to the black-glaze value. The absolute difference is 0.442 percentage points. The brown glaze also contains approximately 30.6% more iron than the unglazed base. The black glaze contains approximately 16.6% more iron than the unglazed base. These measurements establish a systematic variation in iron concentration across the three analyzed regions. 4.3. Theoretical Iron-Oxide Equivalents Table 2. Elemental iron and theoretical Fe₂O₃ equivalents Region Fe (wt%) Fe₂O₃ equivalent (wt%) Brown glaze 4.134 5.91 Black glaze 3.692 5.28 Unglazed base 3.166 4.53 The calculated Fe₂O₃ equivalents fall within a range relevant to the study of historical iron-rich Chinese ceramic glazes. The brown glaze has the highest measured iron concentration despite its lighter appearance relative to the black glaze. This result is particularly significant for understanding the coloration of Jian ceramics. It demonstrates that visual darkness does not correspond simply to the total concentration of elemental iron. The appearance of the glaze also depends on iron-bearing phases, local chemistry, optical absorption, microstructure, and firing history. 4.4. Calcium Enrichment in the Glaze The calcium concentrations reveal a particularly pronounced distinction between the glazed regions and the ceramic body. The brown glaze contains 4.180 wt% Ca. The black glaze contains 4.319 wt% Ca. The unglazed base contains only 0.220 wt% Ca. The brown glaze is therefore approximately 19.0 times richer in calcium than the unglazed ceramic base. The black glaze is approximately 19.6 times richer in calcium than the base. This pronounced difference identifies calcium as an important component of the glaze formulation. The result is consistent with the use of calcium-bearing fluxes in traditional Chinese high-temperature ceramic glazes. 4.5. Silicon and Aluminum Distribution The black glaze contains 34.31 wt% Si, compared with 30.14 wt% Si in the brown glaze. The black glaze is therefore relatively enriched in silicon. Aluminum concentrations are similar in the two glazed regions: Brown glaze: 7.89 wt% Al. Black glaze: 8.10 wt% Al. The unglazed ceramic body contains substantially more aluminum, reaching 12.66 wt% Al. These differences distinguish the aluminosilicate ceramic body from the calcium-rich glaze system. 4.6. Comparative Oxide Equivalents Table 3. Selected theoretical oxide equivalents calculated from pXRF elemental concentrations Oxide equivalent Brown glaze (wt%) Black glaze (wt%) Unglazed base (wt%) SiO₂ 64.48 73.40 53.65 Al₂O₃ 14.91 15.30 23.92 Fe₂O₃ 5.91 5.28 4.53 CaO 5.85 6.04 0.31 K₂O 4.70 5.25 3.52 Valu