Gérard Sagon

Raman study of the microstructure, composition and processing of ancient Vietnamese (proto)porcelains and celadons (13–16th centuries)

Selected ancient Vietnamese (proto)porcelains and celadons (13–16th centuries) from the Ha Lan (Nam Ð inh), Chu Ðâu (Nam Sach, Hai Duong) and Hop Le (Binh Giang, Hai Duong) ceramic kilns were studied by chemical analysis, macro- and micro-Raman spectroscopy, thermal expansion and differential thermal analysis. Raman spectra of quartz, cristobalite, rutile, mullite, anatase, iron oxide, amphibole and glassy phases were analysed and their evolutions are used to discuss the ancient ceramic technology (raw materials used, firing procedures of the glaze and body, etc.). Structural composition data taken from thermal expansion measurements and Raman spectroscopy are in good agreement. Particular attention is given to the analysis of glaze for the feasible discrimination between original artefacts and modern copies. On the basis of experimental results, the samples made at Chu Ð au can be considered as true porcelains, whereas those made at Hop Le and Ha Lan had evolutions towards porcelain and high-temperature-fired fine faience, respectively. Copyright

Raman Spectroscopic Investigation of Blue Contemporary Textiles

Reference (natural and synthetic) indigo samples were analysed by Raman spectrometry and only indigotin was detected. ‘Jeans’ refers to a specific garment with respect to both the dye, indigo, and the garment cut; from reference spectra of blue-dyed fibres and threads from garments, it is straightforward to observe by Raman microspectrometry the spectra of dyes fixed on threads without chemical pretreatment. On these supports, the spectrum of indigotin shows extra bands assigned to vibrational modes of Bu symmetry, indicating a loss of the centrosymmetry of the molecule and an alteration of its planarity due to the dyeing process.

Microstructure, composition and processing of 15th century Vietnamese porcelains and celadons

Fifteenth century porcelains and celadons are the most interesting ancient Vietnamese ceramics, both from the material and aesthetic points of view. This paper reports on composition, microstructure and technological processing of the Chu Ðâu-My Xa (Hai Duong province) ceramics. Samples come either from the kiln site or from the Cu Lao Cham (Hoi An) shipwreck. Chemical analysis, scanning electron microscopy, EDX analysis, X-ray diffraction, Raman spectroscopy, thermal expansion/shrinkage and open porosity measurements were systematically performed. The results show the Ca (+K)-based glaze, high-temperature-fired bodies, by one- or multi-step firings. Mullite phase (3Al2O3·2SiO2) was formed in large amount indicating the true porcelain quality of the samples under study. The matrices used for overglaze colouring (e.g., the green, red and metallic-lustre) are lead-based low-firing-temperature glasses. Comparison was made for the structural elements and fluxing agents between the 15th century Vietnamese porcelains and the time-corresponding Chinese ones.