Inside the glassmaker technology: search of Raman criteria to discriminate between Emile Galle and Philippe-Joseph Brocard enamels and pigment signatures

The development of solid-state chemistry at the end of the 19th century offered a variety of routes to colour a glass matrix. Eight enamelled glass objects made by Philippe-Joseph Brocard and two representative objects made by Emile Galle have been analysed using a mobile Raman instrument at the Musee des arts decoratifs (Paris) in order to compare their colouration technology. White, blue, yellow, green, orange, red, brown and black pigments have been identified. If most of the pigment palette is common to both craftsmen and typical of the second half of the 19th century, innovative uses are recognized for Galle (wollastonite as an opacifier, manganese oxides in black mixtures) and Brocard (specific black and grey, pigment mixture, shade modification by small addition of white and red pigments). This preliminary work confirms the potential of Raman spectroscopy, not as a simple analytical method but as a way to document the ancient technology of fine art objects and to discriminate between different genuine productions and/or copies. Copyright (c) 2014 John Wiley & Sons, Ltd.