The Use of Metal Nanoparticles to Produce Yellow, Red and Iridescent Colour, from Bronze Age to Present Times in Lustre Pottery and Glass: Solid State Chemistry, Spectroscopy and Nanostructure

The use of metal nanoparticles dispersed in an optically clear matrix by potters and glassmakers from the Bronze Age up to the present time is reviewed from the solid state chemistry and material science point of view. The nature of metal (gold, silver or copper), the importance of some other elements (Fe, Sn, Sb, Bi) added to control metal reduction in the glass in relation to the firing atmosphere (combined reducing oxidizing sequences, role of hydrogen and water) are considered in the light of ancient Treatises and recent analyses using advanced techniques (FIB-TEM, EXAFS, ... ) and classical methods (optical microscopy, UV-visible absorption). The different types of colour production, by absorption/reflection (red, yellow) or diffraction (iridescence) and the relationship between nanostructure (metal particle dispersion, layer stacking) and lustre colour are discussed. The very specific interaction between light and the metal nanoparticle makes Raman scattering a very useful "bottom up" technique to study the local glass structure around the metal particles as well as to detect incomplete metal reduction or residues tracing the preparation route, hence making it possible to differentiate between genuine artefacts and fakes.