Guan et al. Herit Sci (2021) 9:21 https://doi.org/10.1186/s40494-021-00498-0 RESEARCH ARTICLE Open Access The microstructure of multicolor hare’s fur glaze: the correlation between morphological and compositional characteristics and glaze color Ming Guan1, Baoqiang Kang1, Xiangjun Wei2*, Gen Li1, Cui Jia1, He Li1, Yinzhong Ding1 and Yong Lei1* Abstract The hare’s fur glazed Jian wares characterized by radial fur-like strips, as one of the typical representatives of Chinese ceramics in the 10th-13th century (A.D.), were famous for the aesthetic values in highlighting the color sparkling efects of tea soup, which were one of the indispensable tea wares in tea culture. The fring technology of hare’s fur glaze of Jian wares not only played a crucial role in the development of Chinese ceramic history, but also enlightened the modern imitation technology. The hare’s fur glaze of Jian wares can be further grouped according to the color of strips, of which the yellowish-brown hare’s fur glaze (yellowish-brown matte strips), gold hare’s fur glaze (golden shiny strips) and silver hare’s fur glaze (bright silvery strips) were the most representative types. Epsilon-Fe2O3, a specifc metastable crystal phase, has become a research hotspot as the chromogenic crystals of hare’s fur glaze, however, the comparative analysis focused on the correlation between ε-Fe2O3 and the macroscopic glaze color has been barely reported. In our work, the bright color strips (hare’s fur area) and black strips (black glaze area) of silver, gold and yel- lowish-brown hare’s fur glaze were morphologically and compositionally analyzed by SEM and EDS, respectively. The morphological features and compositional diferences of three representative types of hare’s fur glaze samples were summarized, which indicated the diferences in the size, distribution and coverage of crystals and the distribution and contents of materials. It was speculated that high-level of ­Fe2O3 and CaO with low-level of ­SiO2 and ­Al2O3 may relate to the crystallization of ε-Fe2O3. This work helps in laying the foundation of further explanation of the technological diferences of hare’s fur glazes. Keywords: Hare’s fur glaze, Jian wares, SEM, EDS Introduction and the most popular type, which was known for the Te glossy black-brown glazed porcelain was one of the radial strips shaped as the fur of hare. Te hare’s fur glaze representative types of Chinese ceramics, which occu- was also famous for the aesthetic values in highlight- pied a unique place in Chinese ceramic history, especially ing the white color and the sparkling efects of tea soup in the culturally prosperous Song Dynasty (the 10th-13th due to the intensive color comparison, which made it an century A.D.) refecting the pursuit of simplicity and optimal container in tea culture [1]. As the most famous elegance. Of all the black-brown glazed porcelains, the product of Jian kiln, Jian wares were acknowledged as the hare’s fur glaze was considered as the superior quality most typical representatives of the hare’s fur glaze, which not only occupied the most crucial role in the black- *Correspondence: [email protected]; [email protected] brown glaze development in Chinese ceramic history, but 1 The Palace Museum, Beijing, China also profoundly afected the Asian ceramic history, espe- 2 Shanghai Advanced Research Institute, Shanghai Synchrotron Radiation Facility, Chinese Academy of Sciences, Shanghai, China cially for Japanese ceramics [2]. Te fring technology of © The Author(s) 2021. 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The Creative Commons Public Domain Dedication waiver (http://creat​iveco​mmons​.org/publi​cdoma​in/ zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Guan et al. Herit Sci (2021) 9:21 Page 2 of 10 hare’s fur glazed Jian wares also enlightened the modern on the correlation between the microscopic structures of imitation technology of hare’s fur glaze [3]. ε-Fe2O3 and the macroscopic glaze color, since ε-Fe2O3 Te hare’s fur glaze of Jian wares can be further was found on the golden, silvery and brownish glazes in grouped based on the color of strips, of which the yellow- one kiln. Te comparison of ε-Fe2O3-rich glaze in difer- ish-brown hare’s fur glaze, gold hare’s fur glaze and silver ent types of hare’s fur glazed Jian wares unearthed from hare’s fur glaze were the most representative types. In the Shuiji kiln was expected to provide enlightenment for previous study, Chen et al. proposed the scientifc cate- the controllable synthesizing method for specifc ε-Fe2O3 gory criteria of the three types of hare’s fur glaze based crystals and other corresponding researches. on the comparation of the samples from Luhuaping kiln In this work, the bright color strips (hare’s fur area) based on stereoscopic microscope [4]. Specifcally, [1] and black strips (black glaze area) of three representa- the yellowish-brown hare’s fur glaze was characterized tive types of hare’s fur glaze samples (silver, gold and yel- by matte yellowish-brown strips with the largest number lowish-brown) were compared. Te microstructures of of samples; [2] the gold hare’s fur glaze had golden yel- the hare’s fur area and black glaze area in diferent types low strips which shined golden gloss with certain sam- of samples were visualized based on scanning electron ples; [3] the silver hare’s fur glaze was characterized by microscope (SEM). Besides, energy dispersive spectros- vaporous white strips or bright silver strips with shine copy (EDS) was applied for elemental imaging microanal- without obvious crystallization on the glaze surface, the ysis and semi-quantitative analysis. In combination of the quantity of which was extremely rare. Te multiple types morphology and element distribution, the micromorpho- of hare’s fur glaze refected the perfect aesthetical pursuit logical characteristics and component diferences of the of tea wares, among which the silver hare’s fur glaze with silver hare’s fur glaze, gold hare’s fur glaze and yellowish- silvery and radial strips were the most acclaimed type brown hare’s fur glaze in Shuiji kiln were discussed in the since the silvery streaks perfectly presented the sparkling present work, which elucidated the correlation between tea soup. Te admiration and status of silver hare’s fur the microstructure of ε-Fe2O3 crystals and the glaze glaze could be caught a glimpse from the “Da Guan Cha color. Tis work helps in investigating the technological Lun” written by the emperor Huizong of Song Dynasty diferences of three typical hare’s fur glazes. (A.D. 1082–1135). However, due to the difculty of fr- ing process and low yield, the extant amount of hare’s fur Materials and methods glazed Jian wares samples was scarce, especially for the Samples silver hare’s fur glaze, resulting in the lack of responding researches [4]. Te hare’s fur glaze samples were unearthed in the Jian Te surface crystallization on the iron-rich porcelain kiln relics (Shuiji, Jianyang District, Nanping City, Fujian glaze, including the dendritic microstructure of iron Province), which were supposed to be belonged to South- oxides, has been widely studied in historical sherds and ern Song Dynasty (the 12th-13th century A.D.). Te imitations in recent years [5–8]. Interestingly, epsilon- samples were numbered and grouped based on previ- ous classifcation criteria [1, 4], as shown in Fig. 1. Spe- Fe2O3 (ε-Fe2O3), a specifc metastable crystalline poly- morph of iron oxide [9], has become a research hotspot cifcally, the samples with bright shiny silver strips were as the chromogenic crystals of sauce, oil spot, and hare’s grouped as silver hare’s fur glaze (FJS-004 and FJS-006), fur glazes [10–13]. As a promising magnetic material, the ones with golden glossy yellow strips as gold hare’s fur glaze (FJS-005 and FJS-007) and the ones with yel- ε-Fe2O3, has been limited in application due to the dif- culty in modern chemical synthesis [14–16]. However, as lowish-brown matte strips as yellowish-brown hare’s fur glaze (FJS-008 and FJS-010). Te samples were gen- early as the 7th-10th century of ancient China, ε-Fe2O3 was successfully synthesized on the colored glaze of tly wiped of the dust on the surface with air-laid paper Changsha kiln [17], which was successively reported the immersed with ethanol. existence in the brown glaze of Yaozhou kiln of North- ern Song Dynasty (the 10th-12th century A.D.) [11], the The micromorphological analysis based on SEM sauce glaze of Qilizhen kiln of Southern Song Dynasty Te MIRA3 feld emission scanning electron microscope (the 12th-13th century A.D.) [18], the hare’s fur glaze (FE-SEM, TESCAN) was applied for the micromorpho- and oil spot glaze of Southern Song Dynasty [19, 20], the logical analyses of the silver, gold and yellowish-brown hare’s fur glaze of Jizhou kiln [21], and the purple-gold hare’s fur glaze samples.