A non-invasive screening study of varnishes applied to three paintings by Edvard Munch using portable diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS)

Thierry Ford,Tine Frøysaker,Ella Hendriks,Adriana Rizzo,Francesco Caruso

doi:10.1186/s40494-019-0327-1

Abstract

The availability and popularity of portable non-invasive instrumentation for the study of paintings has increased due to a shift away from using micro-invasive techniques. Fourier transform infrared spectroscopy (FTIR) is a successful and established technique for the characterisation of organic materials in varnish coatings and paint films. In addition, portable FTIR (pFTIR) spectrometers allow for non-invasive in situ analyses. This overcomes the disadvantages associated with micro-sampling and reproducibility issues encountered in analysis at a specific spot, as pFTIR enables examination of the whole painting. However, the practical applications and capabilities of pFTIR as a suitable screening method for the chemical characterization of varnish coatings in painting collections require systematic evaluation. This study involves a selection of three paintings from the collection of 57 works by Edvard Munch belonging to The National Museum of Art in Norway. Its focus is the identification of the non-original varnish types that were applied by the museum. Between 1909 and 1993, the Museum was embroiled in a varnish controversy due to their application of, first natural and then synthetic, varnish coatings to 48 of these Munch paintings. A series of public debates arose about the Museum’s varnishing practice, which ran counter to the artist’s usual custom of leaving paint surfaces unvarnished (or occasional locally varnished). The three paintings were screened using a pFTIR spectrometer. Different regions of the varnished and unvarnished painted surfaces were analysed with Portable Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS). These paintings date from 1887 to 1891 and are documented as having been treated at the Museum with one of the following types of natural or low-molecular-weight synthetic varnish coatings: dammar, mastic, polycyclohexanone (Laropal K 80 from BASF) and reduced or hydrogenated cyclohexanone-co-methyl-cyclohexanone (MS2A from Howards of Ilford). Surface microscopy and multispectral imaging of the varnished surfaces initially assisted the mapping and choice of areas relevant for the portable DRIFTS measurements. Portable X-Ray fluorescence and surface gloss readings were also made at the pFTIR spot locations to complement the results. Using known dry varnish samples, pFTIR reference spectra were obtained and a DRIFT spectral library was also created from known historic batches of varnishes used by the museum. These were then compared with the in situ pFTIR surface readings taken from the paintings together with additional spectra acquired from a selected number of micro-samples from the same spot locations. The preliminary measurements provided an insight into the capabilities, limitations and practical aspects of using portable DRIFTS for the identification of varnish coatings present in this specific selection of Munch paintings.

Highlights

The National Museum of Art (NM) in Oslo, Norway, houses one of the largest and the most important single collections by the expressionist artist Edvard Munch (1863–1944).1 It comprises 57 paintings from Munch’s earlier period and the bulk of the collection was acquired within a 30-year period (1908–1938) by the museum’s first director, Jens Thiis (1908–1941) [1]
This study aimed to test the versatility of portable Fourier transform infrared spectroscopy (FTIR) (pFTIR) for the surface analysis of non-original varnish coatings on three Munch paintings from the NM’s collection
It was possible to align the pFTIR results with information derived from archival sources, but the discrepancy observed with Night in Nice highlighted the need for a reliable and comprehensive methodology for the identification of the varnish coatings

Summary

Introduction

The National Museum of Art (NM) in Oslo, Norway, houses one of the largest and the most important single collections by the expressionist artist Edvard Munch (1863–1944). It comprises 57 paintings from Munch’s earlier period and the bulk of the collection was acquired within a 30-year period (1908–1938) by the museum’s first director, Jens Thiis (1908–1941) [1]. The National Museum of Art (NM) in Oslo, Norway, houses one of the largest and the most important single collections by the expressionist artist Edvard Munch (1863–1944).. The National Museum of Art (NM) in Oslo, Norway, houses one of the largest and the most important single collections by the expressionist artist Edvard Munch (1863–1944).1 It comprises 57 paintings from Munch’s earlier period and the bulk of the collection was acquired within a 30-year period (1908–1938) by the museum’s first director, Jens Thiis (1908–1941) [1]. Thiis reopened the newly refurbished South wing of the former National Gallery of Art and set a precedent in terms of how the Munch paintings should be presented and displayed in the museum. A selection of the newly acquired Munch paintings was hung together on a single wall in the East galleries (Fig. 1) and J. Thiis made no secret of the fact that Munch’s paintings deserved to be displayed as an ensemble and, ideally, in one room dedicated to the artist [1]

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