Joen J. Hermans

Rijksmuseum Amsterdam · Conservation, Restauration and Research

Pigments in oil paint are bound by a complex oil polymer network that is prone to water-related chemical degradation. We use cryo-Fourier-transform infrared spectroscopy and differential scanning calorimetry to study how water distributes inside zinc white oil paint. By measuring water freezing and melting transitions, we show that water-saturated...

The Night Watch, painted in 1642 and on view in the Rijksmuseum in Amsterdam, is considered Rembrandt’s most famous work. X-ray powder diffrac- tion (XRPD) mapping at multiple length scales revealed the unusual presence of lead(II) formate, Pb(HCOO)2, in several areas of the painting. Until now, this compound was never reported in historical oil pa...

Oil paintings are complex, multi-layered systems that are prone to chemical degradation. While it is increasingly recognised that water plays an important role in these degradation reactions, little is known about moisture concentrations in oil paint systems and their temporal variation in response to fluctuating ambient air humidity. This knowledg...

The crystallization of metal soaps in polymer matrices is a complex process that affects the stability of oil paintings, as well as the properties of commercial ionomer materials. In the context of conservation of paintings, it is crucial to investigate the influence of solvent exposure on such detrimental chemical processes. Using Fourier transfor...

The Night Watch, painted in 1642 and on view in the Rijksmuseum in Amsterdam, is considered Rembrandt's most famous work. X‐ray powder diffraction (XRPD) mapping at multiple length scales revealed the unusual presence of lead(II) formate, Pb(HCOO)2, in several areas of the painting. Until now, this compound was never reported in historical oil pain...

The Night Watch, painted in 1642 and on view in the Rijksmuseum in Amsterdam, is considered Rembrandt’s most famous work. X‐ray powder diffraction (XRPD) mapping at multiple length scales revealed the unusual presence of lead(II) formate, Pb(HCOO)2, in several areas of the painting. Until now, this compound was never reported in historical oil pain...

Metal soap formation is recognised as a critical degradation mechanism in historical oil paintings, which threatens the preservation of museum collections worldwide. Metal soaps form via a complex sequence of chemical reactions between metal ions released by the pigments and saturated fatty acids originating from the drying oil. The latest advances...

The crystallization of metal soaps in oil paint is an important chemical phenomenon that affects the appearance and structural stability of many works of art. A deep understanding of the structural transitions that occur during crystallization and their kinetics will help to support conservation decisions that minimize future detrimental change to...

The phenomenon of metal soap formation and growth has been identified in a large number of historical oil paintings displayed in museum collections worldwide. Metal soap formation and growth may trigger different types of degradation mechanisms. Despite the vast literature on the chemical process associated with metal soap formation, its influence...

Oil paint binding media are complex polymer networks that harbor populations of metal ions. Understanding of the reactivity of these metal ions, often closely linked to paint degradation, is crucial to support paintings conservation efforts. By developing a spectrum fitting approach for the analysis of Fourier transform infrared spectra, we have st...

The formation of crystalline zinc soaps (zinc salts of fatty acids) in oil paint layers is a common sign of paint degradation. In this study, we have used infrared spectroscopy to systematically identify differences in structure and composition of crystalline zinc soap phases, and report data analysis methods for structure attribution in challengin...

Almost seventy years after artists such as Frank Stella (1936), Andy Warhol (1928-1987), James Rosenquist (1933-2017), Herb Aach (1923-1985) and Richard Bowman (1918-2001) started to incorporate Daylight Fluorescent Pigments (DFPs) in their artworks, the extent of the conservation problems that are associated with these pigments has increased progr...

Metal soap formation is one of the most wide-spread degradation mechanisms observed in historical oil paintings, affecting works of art from museum collections worldwide. Metal soaps develop from a chemical reaction between metal ions present in the pigments and saturated fatty acids, which are released by the oil binder. The presence of large meta...

The exposure of oil paintings to organic solvents for varnish removal or to water for the removal of surface dirt can affect the chemical and physical properties of oil paint in an undesired way. Solvents can temporarily plasticise and swell the polymerised oil paint binding medium, enhancing both the thermal mobility and mechanical displacement of...

Abstract The science of oil paint cleaning is an interdisciplinary and challenging field of study due to the complex nature of both paintings and cleaning materials. The topic requires an intimate and iterative collaboration between conservation scientists and paintings conservators. In such an interdisciplinary field, it can sometimes be difficult...

Although the concentration of carboxylic acid (COOH) groups is crucial to understand oil paint chemistry, analytical challenges hindered COOH quantification in complex polymerised oil samples thus far. The concentration of COOH groups is important in understanding oil paint degradation because it drives the breakdown of reactive inorganic pigments...

The molecular structure around metal ions in polymer materials has puzzled researchers for decades. This question has acquired new relevance with the discovery that aged oil paint binders can adopt an ionomer structure when metal ions leached from pigments bind to carboxylate groups on the polymerized oil network. The characteristics of the metal-p...

The impact of solvent exposure on oil paintings and the differences between solvent application methods are longstanding topics in cleaning studies. Solvent exposure is ideally kept to a minimum, because solvent swelling can lead to the extraction and displacement of reactive paint components. In particular, important concerns are fatty acids displ...

An overview is presented of the current state of understanding of the chemical pathways that lead to the formation of crystalline metal soap phases in oil paints, based on recent experimental work by the authors and supported by relevant literature. Improved (quantitative) interpretation of Fourier-transform infrared (FTIR) spectra has revealed tha...

This paper describes a photoluminescence imaging approach coupled to a synchrotron source (SR-PL imaging) that provides a new, powerful way to probe the processes involved in metal soap formation in paint films, processes that play an important role in the deterioration of paint films in traditional and modern oil paintings.

The Evolution triptych by Piet Mondrian (1911, oil on canvas, Gemeentemuseum Den Haag) presents a case study of a painting that is seriously affected by zinc soap formation, which has resulted in paint delamination and paint loss, particularly in the cadmium yellow paint areas. The paint is extremely fragile, which makes the paintings vulnerable wi...

The privately owned oil painting Composition with Color Planes 4 (1917) by Piet Mondrian (1872–1944) has been the subject of ongoing investigation since 2011. The painting consists of color planes in a field of differing whites. Some of these white areas suffer from delamination issues, in combination with flaking. Previous research demonstrated a...

[This corrects the article DOI: 10.1021/acs.macromol.8b00890.].

In the restoration of paintings, solvent diffusion and swelling of polymeric oil paint binding media are important factors to consider. Common cleaning methods with organic solvents or aqueous solutions could lead to undesirable physicochemical changes in the paint in the long term, though the extent of this effect is not yet clear. We used tailore...

Using the recently developed techniques of electron tomography, we have explored the first stages of disfiguring formation of zinc soaps in modern oil paintings. The formation of complexes of zinc ions with fatty acids in paint layers is a major threat to the stability and appearance of many late 19th and early 20th century oil paintings. Moreover,...

The formation of metal soaps (metal complexes of saturated fatty acids) is a serious problem affecting the appearance and structural integrity of many oil paintings. We used tailored model systems for aged oil paint and time-dependent attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to study the diffusion of palmitic a...

The formation of metal soaps (metal complexes of saturated fatty acids) is a serious problem affecting the appearance and structural integrity of many oil paintings. We used tailored model systems for aged oil paint and time-dependent attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy to study the diffusion of palmitic a...

Infrared spectra of samples from oil paintings often show metal carboxylate bands that are broader and shifted compared to those of crystalline metal soap standards (metal complexes of long-chain saturated fatty acids). Using quantitative attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), it is demonstrated that the bro...

Front Cover: The image depicts four evolutionary stages of the random graph resembling formation of polymer networks from multifunctional monomers. The polymerisation process goes through a phase transition: the network evolves form disconnected monomers, to finite-size molecules, to an infinite, fully-connected structure (gel). Strong preference f...

The cadmium yellow pigment is identified as a mixture of cadmium sulphide and cadmium oxalate. The presence of zinc white was established in samples of areas where the yellow paint film is degraded, not in the intact yellow paints. FTIR and photoluminescence imaging demonstrated that zinc soaps have formed in the degraded paints. Zinc soaps have ac...

The formation and crystallization of metal soaps in oil paint layers is an important issue in the conservation of oil paintings. The chemical reactions and physical processes that are involved in releasing metal ions from pigments and fatty acids from the oil binder to form crystalline metal soap deposits have so far remained poorly understood. We...

The formation of metal soaps is a major problem for oil paintings conservators. The complexes of either lead or zinc and fatty acids are the product of reactions between common pigments and the oil binder, and they are associated with many types of degradation that affect the appearance and stability of oil paint layers. Fourier Transform Infrared...

Lead and zinc soaps are commonly seen as signs of oil paint degradation. The pathway from pigment to metal soaps and their subsequent migration and accumulation are poorly understood, and it is unknown to what extent these processes are influenced by humidity and temperature. In order to understand fully the behavior of metal soaps in paint systems...

A kinetic model was developed as a first step in constructing a mathematical model describing the structural change of an oil paint network consisting of triacylglyceride (TAG) units during long-term degradation. The kinetic model describes the drying stage of linseed oil in terms of the functional groups partially reacting to cross-links from rate...