Probing the chemistry of CdS paints in The Scream by in situ noninvasive spectroscopies and synchrotron radiation x-ray techniques

Abstract

The degradation of cadmium sulfide (CdS)–based oil paints is a phenomenon potentially threatening the iconic painting The Scream (ca. 1910) by Edvard Munch (Munch Museum, Oslo) that is still poorly understood. Here, we provide evidence for the presence of cadmium sulfate and sulfites as alteration products of the original CdS-based paint and explore the external circumstances and internal factors causing this transformation. Macroscale in situ noninvasive spectroscopy studies of the painting in combination with synchrotron-radiation x-ray microspectroscopy investigations of a microsample and artificially aged mock-ups show that moisture and mobile chlorine compounds are key factors for promoting the oxidation of CdS, while light (photodegradation) plays a less important role. Furthermore, under exposure to humidity, parallel/secondary reactions involving dissolution, migration through the paint, and recrystallization of water-soluble phases of the paint are associated with the formation of cadmium sulfates.

Preliminary Investigations into the Alteration of Cadmium Orange Restoration Paint on an Ancient Greek Terracotta Krater

“…It is hypothesized that the residual chloride ions in the terracotta, resulting from either burial or incomplete treatment with HCl to remove burial accretions, and light exposure act as catalysts for the observed alteration. This is consistent with observations in the literature in which mobile chloride ions have been associated with promoting the oxidation of cadmium sulfide [12] as well as making the pigment more sensitive to photo-oxidation [5,27].…”

“…The peaks associated with the cadmium or- The FTIR spectrum of the altered paint from both the mock-ups and krater remained relatively unchanged in comparison to the spectra of the fresh paint. Whilst the formation of different cadmium compounds (for example CdC 2 O 4 , CdCO 3 ) may be identified in the FTIR spectrum [12,15], the strong signal from the acrylic binder prevented their identification if present. No apparent degradation of the acrylic binder was observed in the pyrolysis-GCMS chromatogram.…”

“…Cadmium yellow is composed of cadmium sulfide (CdS) and the incorporation of Se in increasing amounts changes the color from yellow through orange to red. The alteration of cadmium yellow has been reported in paintings by Henri Matisse [5][6][7][8][9], Edvard Munch [9][10][11][12], Vincent Van Gogh [13,14], Pablo Picasso [13,15] and others [13,[16][17][18], all dating from the late 19th-early 20th century, before the stability of pigment was improved [16]. Alteration in areas identified as cadmium sulfide presents itself as either lightening or darkening of the once vibrant pigment.…”

Application of Infrared Reflectance Spectroscopy on Plastics in Cultural Heritage Collections: A Comparative Assessment of Two Portable Mid-Fourier Transform Infrared Reflection Devices

“…Infrared reflection process of optically thick cultural heritage materials is thus a very complex phenomenon resulting in IR spectra difficult to handle. 33–41 Some studies proved the efficiency of using the KK correction on derivative-like bands ( k < 1), 42–44 while not satisfactory results were obtained for this algorithm when applied to reststrahlen bands ( k ≫ 1). 44–46…”

Discoloration of Historical Plastic Objects: New Insight into the Degradation of β-Naphthol Pigment Lakes

“…Plastics in collections are challenging to preserve, as they tend to degrade faster than other materials found in artworks [9][10][11][12][13][14][15][16][17]. Synthetic organic/inorganic pigments also have stability issues [18][19][20][21][22][23][24][25] and their alteration in modern polymeric paints continues to be a subject of ongoing research in art conservation [26][27][28][29][30][31]. Both polymers and pigments are known to be sensitive towards aging, which can lead to color change.…”