Capabilities and limitations of handheld Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for the analysis of colourants and binders in 20th-century reverse paintings on glass

Simon Steger; Heike Stege; Simone Bretz; Oliver Hahn

doi:10.1016/j.saa.2018.01.057

Capabilities and limitations of handheld Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for the analysis of colourants and binders in 20th-century reverse paintings on glass

Spectrochim Acta A Mol Biomol Spectrosc. 2018 Apr 15:195:103-112. doi: 10.1016/j.saa.2018.01.057. Epub 2018 Feb 3.

Authors

Simon Steger¹, Heike Stege², Simone Bretz³, Oliver Hahn⁴

Affiliations

¹ BAM Federal Institute for Materials Research and Testing, Division 4.5, Unter den Eichen 44-46, Berlin, Germany. Electronic address: simon.steger@bam.de.
² Doerner Institut, Bayerische Staatsgemäldesammlungen, Barer Str. 29, Munich, Germany.
³ Conservator for Reverse Paintings on Glass, Garmisch-Partenkirchen, Germany.
⁴ BAM Federal Institute for Materials Research and Testing, Division 4.5, Unter den Eichen 44-46, Berlin, Germany; Centre for the Study of Manuscript Cultures, University of Hamburg, Hamburg, Germany.

PMID: 29414566
DOI: 10.1016/j.saa.2018.01.057

Abstract

A non-invasive method has been carried out to show the capabilities and limitations of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS) for identifying of colourants and binders in modern reverse glass paintings. For this purpose, the reverse glass paintings "Zwei Frauen am Tisch" (1920-22), "Bäume" (1946) (both by Heinrich Campendonk), "Lofoten" (1933) (Edith Campendonk-van Leckwyck) and "Ohne Titel" (1954) (Marianne Uhlenhuth), were measured. In contrast to other techniques (e.g. panel and mural painting), the paint layers are applied in reverse succession. In multi-layered paint systems, the front paint layer may no longer be accessible. The work points out the different spectral appearance of a given substance (gypsum, basic lead white) in reverse glass paintings. However, inverted bands, band overlapping and derivative-shaped spectral features can be interpreted by comparing the spectra from the paintings with spectra from pure powders and pigment/linseed oil mock-ups. Moreover, the work focuses on this method's capabilities in identifying synthetic organic pigments (SOP). Reference spectra of three common SOP (PG7, PY1, PR83) were obtained from powders and historical colour charts. We identified PR83 and PY1 in two reverse glass paintings, using the measured reference spectra. The recorded DRIFTS spectra of pure linseed oil, gum Arabic, mastic, polyvinyl acetate resin and bees wax can be used to classify the binding media of the measured paintings.

Keywords: DRIFT spectroscopy; FTIR; Non-invasive analysis; Reverse painting on glass; Synthetic organic pigments.