Multi‐analytical characterisation of Art Déco dinanderie: Single‐point and map analysis of Jean Dunand's metal artworks

Jean Dunand (1877–1942) was a European artist internationally appreciated at his time for his innovative Art Déco housewares made of hammer‐beaten copper‐based alloys, known as dinanderie. Still uncertain was the nature of the constituting materials; therefore, for the first time, three objects, namely, a bowl, a trinket bowl and a vase, were the target of a multi‐modal work of characterisation. Mobile or benchtop X‐ray fluorescence, Fourier‐transform infrared (FTIR) and Raman spectroscopies were used to adapt the analyses to the shape and size of the artefacts. Elemental analysis verified that the vase consisted of brass Cu70Zn30, whereas the bowl and the trinket bowl were made of nickel silver Cu70Zn19Ni11. The black finishing present on all the artefacts was related to tenorite by Raman spectroscopy, ascribing the patina to an intentional artist's willing and not to spontaneous tarnishing processes. Metal soaps of copper and zinc were documented as degradation products by FTIR spectroscopy. The drawings adorning the vase and the trinket bowl were identified as silver‐based, contrary to what was hypothesised by conservators (i.e., tin‐based) due to conventional Dunand's inlaying technique. Besides single‐point analysis, Raman mapping was performed in‐situ, applying for the first time a Virsa™ Raman Analyser (Renishaw) in the field of cultural heritage. The fibre‐optic‐coupled instrument allowed to comply constantly with the artefacts' geometry thanks to the modular probe and the motorised focus‐tracking stand. The synergic combination of elemental and vibrational analyses resulted successful, providing new and unique information on artist's technique in view of possible restoration interventions.