Application of Raman microscopy to the analysis of china pieces recovered from the English warship HMS Swift sunk near the coast of Patagonia in 1770

STEFANIAK, E.A. LL DARCHUKK CC VAZQUEZZ DD ELKIN YY MAKAROVSKAA KK VAN MEELL AA WOROBIEC AND RR VAN GRIEKEN

Viena

Congreso; 8th International Conference of Infrared and Raman Users Group; 2008

Infrared and Raman Users Group

On 13th March 1770 a British Royal Navy warship sank off the remote and barren coast of Patagonia, in the southwestern Atlantic. Discovered after 200 years, it has become a priceless source of archeological, historical and cultural treasures. Among various items found in the wreck there were “oriental-style ceramics”, among which there were artifacts of blue and white porcelain. They comprise mainly tea bowls and plates, bearing common features of Chinese (oriental) decoration, made exclusively with a blue, underglaze paint. A piece of this white-blue china (ca 7cm x 6cm) was investigated by means of Raman microscopy. The spectra showed the presence of kaolin; however the signal was strongly disturbed by fluorescence. Locally, fine grains of quartz were detectable. The glazing layer was not susceptible to a laser excitation, providing only strong fluorescent radiation. Investigation of the blue pigment was quite challenging, because apparently there were two different blue paints applied for manufacturing this china piece. One of them was “cobalt blue”, recognized by its strong Raman shift at 509 cm-1. This pigment was located on the surface of a mineral layer and under the glazing, which caused a bluish shade of the whole glassy covering. The other one, bright blue, was dissipated around the interface between the glazing and the core. It occurred as tiny blue spots of ca 10 ìm diameter. Its Raman spectrum is very complex, with numerous shifts, of which the stronger are: 590, 680, 748, 1341, 1389, 1452, 1525 cm-1. The ambiguous shape of the Raman spectrum reflects probably a multi-component nature of the mysterious pigment. The Raman microscopy was also complemented by X-ray based techniques – XRF and SEM/EDX. The bulk elemental composition, determined by XRF, showed the main components as SiO2 and Al2O3, minor components: K2O, CaO, MnO, Fe2O3, Co3O4 and trace elements: Ti, Cl, Ni, Rb, Sr, Ba, Ce, Zn, Cu, Zr. SEM/EDX results revealed a distribution of major elements down to 500 ìm below the china surface.