Non-invasive Raman analyses of Chinese huafalang and related porcelain wares. Searching for evidence for innovative pigment technologies

Abstract

Eighteen Chinese painted enamelled porcelains and three Chinese enamelled Yixing stonewares dated to the 16 th to 19 th centuries and kept at the Musée national des arts asiatiques-Guimet (MNAAG), have been analysed with a mobile Raman set-up to identify their enamelling technology. Different Grand Feu (leadless or lead-poor colourless and blue enamel) and Petit Feu (lead-rich red (hematite), yellow and green (Pb-Sn/Sb/X pyrochlore) and black enamels) glazes were respectively identified on wares from the wucai group, the Famille verte group, and the huafalang group. Calcium phosphate was detected in a 17 th century vase as a rare opacifier. Cassiterite was identified in the light green glaze of an imperial huafalang bowl dated to the final period of the Kangxi reign (1662-1722), ca. the 1 st quarter of the 18 th century. Lead arsenate was identified in the blue glaze of two artefacts, a huafalang bowl and a painted enamel water dropper, and in the blue enamel of a 19 th century Yixing teapot. Lead arsenate found in some of the blue enamels appears to arise from the arsenic content in Erzgebirge cobalt ores and not due to voluntary addition. This may prove the use of raw materials or enamel powder imported from Europe in developing these opaque colours. The use of lead arsenate as white opacifier is clear for a water dropper bearing the Yongzheng emperor's mark (r. 1723-1735). The technological palette appears different for the artefacts expected to originate from the same period and provenance (imperial workshop) which is consistent with a period of intense innovation, open to technological skill from abroad -i.e. from French/European painted enamel technology -as revealed by ancient French (Jesuits) and Chinese historical reports. Graphical abstract 2

On‐site Raman study of artwork: Procedure and illustrative examples

“…Complex multicoloured décors for potteries are made by using a succession of thin glaze layers (the thickness being close to 10–20 μm, i.e., larger than the z‐size of the focused spot obtained with ×50 or even ×100 microscope objective) and taking into account the broadening of the spot within the silicate glass. Figure compares the Raman spectra (as recorded, not expanded) collected on the same enamelled wucai porcelain with ×50 (Nikon) and ×200 (Mitutoyo) LWD objectives . The highest intensity of the Raman signature of both the crystalline (pigments) and amorphous (glaze matrix) phases recorded with a ×200 objective is obvious.…”

“…Figure 3 compares the Raman spectra (as recorded, not expanded) collected on the same enamelled wucai porcelain with ×50 (Nikon) and ×200 (Mitutoyo) LWD objectives. [52,53] The highest intensity of the Raman signature of both the crystalline (pigments) and amorphous (glaze matrix) phases recorded with a ×200 objective is obvious.…”

“…Gemstones [30,33,37,40,41,126,127] Pigments of illuminated manuscripts [48,128,129] Wall paintings and frescoes [130,[132][133][134][135][136]144] Rock art [137][138][139][140][141] Buildings and stones [117][118][119]142,143] Glass, glaze, and pottery [31,32,43,[49][50][51][52][53][54]91,92,101,[103][104][105][106] Bronze corrosion and patina [123] Iron/steel corrosion layer and patina [114,116,117] Paintings pigments [13,125,…”

Comparative analysis of wucai Chinese porcelains using mobile and fixed Raman microspectrometers

“…Chinese enamelled precious artefacts [14] in addition to elemental composition measurements of some shards [15][16][17][18][19][20][21][22][23] showed that Chinese craftsmen used different types of cobalt sources including arsenicrich cobalt ores similar to those used in Europe for soft-paste porcelain [5,11] and Limoges enamels [24], and manganese-and/or iron-rich ores of Asian origins [16][17][18]25] to make blue decorations.…”

“…Recent studies demonstrated that useful information can be obtained by non-invasive mobile techniques, based on portable XRF and Raman spectroscopies [14,[24][25][26][27][28][29]. The great advantages of Raman microspectroscopy are: i) its non-invasive character that allows studying very precious items, ii) the availability of high sensitivity mobile instruments that permit the measurements of many objects per day in exhibition, ancient tombs or storage rooms, iii) a great efficiency in the identification of many colouring agents, even at low concentration and iv) the possibility of very local and in-depth analysis.…”