Authenticity screening of stained glass windows using optical spectroscopy

Abstract

Civilized societies should safeguard their heritage as it plays an important role in community building. Moreover, past technologies often inspire new technology. Authenticity is besides conservation and restoration a key aspect in preserving our past, for example in museums when exposing showpieces. The classification of being authentic relies on an interdisciplinary approach integrating art historical and archaeological research complemented with applied research. In recent decades analytical dating tools are based on determining the raw materials used. However, the traditional applied non-portable, chemical techniques are destructive and time-consuming. Since museums oftentimes only consent to research actions which are completely non-destructive, optical spectroscopy might offer a solution. As a case-study we apply this technique on two stained glass panels for which the 14th century dating is nowadays questioned. With this research we were able to identify how simultaneous mapping of spectral signatures measured with a low cost optical spectrum analyser unveils information regarding the production period. The significance of this research extends beyond the re-dating of these panels to the 19th century as it provides an instant tool enabling immediate answering authenticity questions during the conservation process of stained glass, thereby providing the necessary data for solving deontological questions about heritage preservation.

Analysis of chromophores in stained-glass windows using Visible Hyperspectral Imaging in-situ

“…Copper ions usually give a turquoise color on soda-lime silicate glasses. The Cu 2+ -ions have an electronic configuration 3d 9 in octahedral coordination, which permits the electronic transition 2 E → 2 T2 (790 nm) (Fig. 5 b).…”

“…Optical spectroscopy in the UV-VIS-NIR range is the most frequent technique used for the analysis of chromophores, usually in absorption or transmission mode [4][5][6][7][8][9][10][11][12], because it permits to identify the chemical state of the chromophores and the nature of the coloring phenomenon; but it is a destructive technique because it needs a thin and polished sample. For this reason, only glass fragments rejected during the restoration process have been generally analyzed [4,8,9,[13][14][15][16]. It is also possible to perform this analysis by reflectance [17], but the spectra normally have lower quality [18].…”

Hyperspectral imaging with a TWINS birefringent interferometer

“…Finally, we demonstrate HSI of a stained glass window, whose plates typically exhibit strong absorption bands located at well-defined wavelengths. Since window glass manufacturing has changed throughout time, spectral characterization is a means to determine the composition of glasses and of their coloring agents, to assess the authenticity of ancient windows [39]. Figure 6 shows the results from HSI of a portion of an artistic glass window at Santo Spirito Church in Milan (Italy), designed in 1969 by A. M. Nardi .…”

Recent progress in instrumental techniques for architectural heritage materials

“…Their energies are in the range from near infrared (750-2500 nm), through visible (400-750 nm), to ultraviolet (200-400 nm). Both UV and Vis spectroscopies are extremely important to architectural heritage because they can deal with the measurement of materials related to colors originated from pigments [176][177][178], dyes [179,180], stained glasses [181,182], etc. From the physico-chemical point of view, these spectroscopies give us insight into the electronic mechanisms of color [40].…”