Please cite this article in press as: M. Aceto, et al., A fast non-invasive method for preliminary authentication of mediaeval glass enamels using UV–visible–NIR diffuse reflectance spectrophotometry, Journal of Cultural Heritage (2020), https://doi.org/10.1016/j.culher.2020.05.003 ARTICLE IN PRESS G Model CULHER-3780; No. of Pages 8 Journal of Cultural Heritage xxx (2020) xxx–xxx Available online at ScienceDirect www.sciencedirect.com Original article A fast non-invasive method for preliminary authentication of mediaeval glass enamels using UV–visible–NIR diffuse reflectance spectrophotometry Maurizio Aceto a,b,∗ , Gaia Fenoglio c,d , Maria Labate c,d , Marcello Picollo e , Mauro Bacci e , Angelo Agostino c,d a Dipartimento di Scienze e Innovazione Tecnologica (DiSIT), Università degli Studi del Piemonte Orientale, viale Teresa Michel, 11, 15121 Alessandria, Italy b Centro Interdisciplinare per lo Studio e la Conservazione dei Beni Culturali (CenISCo), Università degli Studi del Piemonte Orientale, via Manzoni, 8, 13100 Vercelli, Italy c Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria, 7, 10125 Torino, Italy d Nanostructured Interfaces and Surfaces Center of Excellence (NIS), via P. Giuria, 7, 10125 Torino, Italy e Istituto di Fisica Applicata “Nello Carrara” del Consiglio Nazionale delle Ricerche (IFAC-CNR), via Madonna del Piano, 10, 50019 Sesto Fiorentino (FI), Italy a r t i c l e i n f o Article history: Received 14 January 2020 Accepted 11 May 2020 Available online xxx Keywords: FORS XRF Champlevé Enamels Reflectance Limoges a b s t r a c t In this work we used UV–visible–NIR diffuse reflectance spectrophotometry with optic fibres (FORS) in order to point out differences between mediaeval and 19th–20th century champlevé enamels previ- ously analysed with X-ray fluorescence spectrometry (XRF). FORS spectra of enamels collected in diffuse reflectance mode made it possible to obtain information useful not only for identifying the colourants of the enamels, but also for evaluating the authenticity of the artworks. By means of pattern recogni- tion techniques, it was possible to highlight relevant spectral features useful for the discrimination of objects, the authentication of which was previously verified by means of elemental analysis (XRF). The role of transition metal ions, mainly iron and manganese, in the reflectance spectrum, has been critically discussed. FORS proved to be a highly reproducible technique, capable of detecting the chromophores in a glass matrix in a non-invasive and rapid manner. A comparison with historically accurate refer- ence glass and enamels, together with data from other analytical techniques, was essential for validating the method. Furthermore, once the FORS methodology was defined, the results obtained showed great accuracy and reliability. © 2020 Elsevier Masson SAS. All rights reserved. 1. Introduction Glass enamels can be considered to be among the most relevant jewellery products during the Middle Ages, particularly in regard to productions in Limoges (France) and in the Byzantine areas. These artworks usually consisted of a metallic part in copper alloy, inside of which (or over which) vitreous enamels of different colours and shapes were applied. The main technique used by Limoges artisans for enamelling was champlevé or “raised field”: artworks charac- terised by the use of this technique were produced in large numbers during the 12th–15th centuries in the form of medallions, crosses, ∗ Corresponding author at: Dipartimento di Scienze e Innovazione Tecnologica (DiSIT), Università degli Studi del Piemonte Orientale, viale Teresa Michel, 11, 15121 Alessandria, Italy. E-mail addresses: maurizio.aceto@uniupo.it (M. Aceto), m.picollo@ifac.cnr.it (M. Picollo), m.bacci@ifac.cnr.it (M. Bacci), angelo.agostino@unito.it (A. Agostino). reliquaries, book covers, etc. In the champlevé technique, the sur- face of a metal object was worked in order to obtain cells (champs or fields) that were then filled with powdered vitreous enamel. After firing, and thus bringing the vitreous materials to melt, the consolidated surface was polished [1]. Due to the considerable value of the original pieces, Byzan- tine and Limoges enamels have always been associated with fakes. Replicas of ancient artworks were produced on an almost indus- trial scale during the 19th and 20th centuries, in order to meet the great demand from the antiquarian market. Many of these replicas, after changing hands many times, eventually ended up in museums or private collections labelled as original mediaeval pieces. This is not surprising considering the fact that, having been produced by skilful artisans, most of the 19th–20th centuries reproductions are generally indistinguishable from the original ones to the naked eye. Despite this, even if they follow ancient formulations, 19th–20th centuries artisans have used “modern” raw materials for their pieces, and this constitutes a favourable point for the identification https://doi.org/10.1016/j.culher.2020.05.003 1296-2074/© 2020 Elsevier Masson SAS. All rights reserved.