This paper introduces a new set-up for the determination of colour change on cultural heritage objects, referred to herein as a stereo-microfading tester. The system uses high quality optics through the implementation of a stereo-microscope as its central element. This technology enables new developments such as incorporation of high quality imaging systems, and separation of fading and colour measurement processes. This paper describes this new micro-fading set-up and evaluates its performance against traditional devices based on the measurement of blue wool standards. The results show a correlation between the fading performance obtained on different devices while highlighting a significant variability inherent to the blue wool samples

Effective care of large-scale museum collections requires planning that includes the conservation treatment of specific groups of art works, such as appropriate cleaning strategies. Optical coherence tomography (OCT) has been successfully applied as a non-invasive method for the stratigraphic visualisation of the uppermost transparent and semi-transparent layers in paintings, such as varnishes. Several OCT case study examples have further demonstrated the capabilities of the non-contact interferometric technique to measure the thickness of the various varnish layers, to help monitor cleaning and associated optical changes, and to detect past restorations. OCT was applied for the detection of varnishes to 13 paintings by Edvard Munch (1863–1944) owned by the Norwegian National Museum of Art. The paintings have a controversial and complex varnish history and are displayed as a group according to their acquisition legacy. A prototype high-resolution portable SdOCT instrument was used in combination with complementary imaging techniques. Questions concerning thickness, stratigraphy and the identification/location of the artist’s original varnish layers and/or pigmented glazes were addressed. Findings confirmed the complexity of the historical layers present and provided new evidence for Munch’s use of transparent and semi-transparent layers as part of an occasional, localised varnishing and/or glazing technique.

Recent studies in which X-ray beams of macroscopic to (sub) microscopic dimensions were used for non-destructive analysis and characterization of pigments, paint micro samples and/or entire paintings by Vincent van Gogh are concisely reviewed. The overview presented encompasses the use of laboratory and synchrotron radiation-based instrumentation and deals with the use of several variants of X-ray fluorescence (XRF) as a method of elemental analysis and imaging as well as with the combined use of X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). Microscopic and macroscopic XRF are variants of the method that are well suited to visualize the elemental distribution of key elements, mostly metals, present in paint multi layers, either on the length scale from 1–100 μm inside micro samples taken from paintings or on the 1–100 cm length scale when the (subsurface) distribution of specific pigments in entire paintings is concerned. In the context of the characterization of van Gogh's pigments subject to natural degradation, the use of methods limited to elemental analysis or imaging usually is not sufficient to elucidate the chemical transformations that have taken place. However, at synchrotron facilities, combinations of μ-XRF with related methods such as μ-XAS and μ-XRD have proven themselves to be very suitable for such studies. Their use is often combined with microscopic Fourier transform infra-red (μ-FTIR) spectroscopy since this method delivers complementary information at more or less the same length scale as the X-ray microprobe techniques. Also in the context of macroscopic imaging of works of art, the complementary use of X-ray based and infra-red based imaging appears very promising; some recent developments are discussed.

The colors of Van Gogh’s landscape painting Field with Irises near Arles have changed considerably. To digitally reconstruct its original colors, we use an unprecedented broad scientific analysis and experimental art technological approach, by physically reconstructing oil paints of all pigments used by Van Gogh. We closely match the original paints, and for the first time determine all the optical properties involved. The investigation led to a digital image representing the original colors as good as possible.We found that for the digital color reconstruction it is important to take into account that museum lighting is often relatively dark in order to better preserve paintings. Since this affects the best way of representing the reconstructed colors on the display, we adapted the digital reconstructed image. We also corrected for the technical specifications of the electronic display on which the reconstructions will be displayed in the museum.Based on the reconstruction we conclude that the original colors in the painting used to be much brighter, and agreed much better with Van Gogh’s own description of the color composition of this painting. We show that unlike the current colors of the painting, the reconstructed colors are consistent with the color theories on which Van Gogh based his work.

This chapter provides a description of colour changes in the Amsterdam Sunflowers due to chemical alteration of pigments, with a focus on geranium lakes and chrome yellows.

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.

This chapter explores the methods and materials of Vincent van Gogh’s Sunflowers, the painting now in the Van Gogh Museum, Amsterdam. Comprehensive physical and chemical investigations were performed using a range of non-invasive, in situ techniques combined with sample analysis. The results help to elucidate different stages of the artist’s working process, from making the canvas support, to the first charcoal sketch, the palette used, mixing and application of colour, paint texture and brushwork, as well as a wooden strip extension added late in the painting process. Comparisons are made with Van Gogh’s first painting of Sunflowers against a yellow background, now at the National Gallery in London.

Chapter 1 presents the history of research on Van Gogh's Sunflower paintings as context for the most recent study. It explains current approaches and the state-of-the art methods used during the last campaign of investigation.

Drawing on past research and the pioneering case studies of metal soap degradation published more than 15 years ago, this paper reviews the early findings of metal soap-related degradation in seventeenth-century oil paintings carried out by the MOLART and De Mayerne group of researchers in the Netherlands. The various manifestations of lead soap alterations identified are described: aggregates and associated pinpoint losses and texture alterations, insoluble efflorescent crusts, and darkening due to increased transparency from saponification of lead white paints. Mention is made of degradation phenomena associated with other metal soaps, potassium, calcium, copper, aluminum, and especially zinc soaps. A brief history of metal soaps is also presented. Finally, the essay looks at the implications for conservation in the light of recent advances in our understanding of the underlying mechanisms of metal soap formation, and discusses the challenges currently faced in treating and caring for works of art affected by metal soap alterations.