Double layers glaze analysis of the Fujian export blue-and-white porcelain from the Witte Leeuw shipwreck (1613)

Raman identification of the different glazing technologies of Blue-and-White Ming porcelains

“…2 for the São Jão PS, Nossa Senhora, Santo Alberto b and Mombasa shards confirms that the drawing of the blue decoration was made for these specimens on the unfired (green) body and the glaze powder precursor deposited upon it before the firing. Double-layer glazing was claimed by Wen et al from a cross-sectional image for one shard and explained on the basis of a double glazing step, as reported for the Fujian (Zhangzhou) kilns by Zhou et al 45 and Zhang et al 46 If a double-layer could be recognized on the Mombasa and one of the Santo Alberto(b) shards (Fig. 2) it would be difficult to assign this feature to a double glazing step and it is likely this can be ascribed to the marine corrosion at least for San Alberto (b) shards.…”

“…Zhang et al 46 showed that the presence of double-layered glazing existed for Kraak wares. Element distribution mapping clearly showed that the surface glaze layer is richer in calcium, as we have observed her for some blue decoration (we observe similar feature Fig.…”

“…However for most of the samples they studied they could not detect cobalt. The Raman spectra of Zhang et al 46 were recorded using the 785 nm laser line excitation, that could not permit the detection of the vibrational signature of the Si-O network, but only fluorescence emission and consequently their assignment and conclusions derived from their Raman spectra are rendered irrelevant: they assign the 1350 cm -1 feature which is really a fluorescence band, already observed in ref. 3 (spectra also recorded with 785 nm excitation), to the asymmetric stretching vibration of SiO 4 tetrahedra although only the symmetrical stretching modes contribute significantly to Raman scattering and these are located between ~850 and 1100 cm -1 according the degree of polymerization of the silicate matrix.…”

pXRF Data Evaluation Methodology for On-Site Analysis of Precious Artifacts: Cobalt Used in the Blue Decoration of Qing Dynasty Overglazed Porcelain Enameled at Customs District (Guangzhou), Jingdezhen and Zaobanchu (Beijing) Workshops

“…The A 615 bowl mark is rich in Mn, as observed for artifacts produced during the Ming Dynasty [23,26,27,29,[70][71][72][73][74][75][76][77][78][79][80][81][82][83][84][94][95][96][97][98][99][100][101]. A 'return' to traditional Chinese techniques has already been observed for Yongzheng productions [25].…”

“…For a long time, efforts have been made to identify the elements associated with cobalt, allowing the production mining to be identified [23,29,[73][74][75][76][77][78][79][80][81][82][83][84][85][86][87]. Thus, it is considered that during the Yuan Dynasty (1271-1368) the cobalt used was mainly imported from Iran or perhaps even Europe, therefore from the second type [23,[73][74][75][76][77][78][79][80][81][82][83][84][85][86][87], while Asian cobalts (from China, Vietnam and Malaysia/Indonesia), which are rich in Mn and Fe were used [23,26,27,29,[73][74][75][76][77][78][79][80][81][82]…”