This poster abstract was presented at the IIC congress The Objtect in Context: Crossing Conservation Boundaries in Munich, 2006.
by Philip Klausmeyer and Morwenna Blewett
A painting by the Dutch Fauve artist Kees Van Dongen (Reclining Nude) was given recently as a gift to the Worcester Art Museum. Van Dongen worked in Paris from the turn of the twentieth century until his death in 1968.
Technical analysis was initiated to glean information about the artist’s materials and techniques, and to answer specific questions that arose in the course of treating the painting. Examinations of other works by the artist were also conducted to inform the observations and conclusions drawn from the study of the Worcester painting.
Kees Van Dongen generally left his paintings unvarnished, but on some paintings he chose to selectively varnish some areas of the impasted highlights, particularly in areas of flesh or drapery. An example of this is found in the Portrait of Anna de Brancovan, from the collection of the Stedelijk Museum, Amsterdam. This painting still has the artist’s original localized varnish applications on various areas of the figure.
A sample of the locally-applied varnish was examined using polarized light microscopy. When the sample was then pressed with a diamond point, it shattering in a manner characteristic of a brittle varnish. Viewed under ultraviolet epi-illumination, the sample exhibited the strong fluorescence associated with an
aged natural resin varnish. Fourier transform infrared (FTIR) microspectroscopy was also used to analyze the sample and produced a spectrum that is consistent with a natural resin varnish, specifically that of mastic resin.
While the Worcester painting does not have an overall varnish layer, remnants of some localized applications appear on the white impasto highlights of the bedclothes. Like the Stedelijk painting, FTIR analysis of the varnish remnants on the Worcester painting showed a spectral match for mastic varnish. Similarities in the selective application of natural resin varnish on both the Stedelijk and the Worcester paintings suggests a common aspect of the artist’s working method; the function of the varnish being to enhance the luminosity in specific areas.
Surface examination of the painting also revealed small, transparent, bead-shaped exudates from some painted areas. This material was found in one area of the figure’s flesh and in a number of other gray areas in the outer margins of the background. Though when viewed in visible light these areas of paint seemed to have the same body and quality of brushwork seen in surrounding flesh paint, examination in ultraviolet light showed these areas to have a fluorescence distinct from the rest of the surface. The status of this paint was investigated and it was concluded that it was not later overpaint, but an artist’s revision or addition in each particular area.
As with the varnish, a sample of the exudate was taken from the flesh-toned area and examined microscopically under transmitted light and ultraviolet epi-illumination. Pressing out the sample produced no fracturing and instead revealed the sample’s malleable properties. Examination under transmitted
light revealed the heterogeneous nature of the sample, containing two distinctly different components, one of which appeared to be pigmented. In ultraviolet illumination the two components exhibited different fluorescence properties. FTIR microspectroscopy yielded a spectral match with gum arabic, sucrose (probably honey), and zinc stearate.
Based on the physical appearance of the paint surface and the fact that gum arabic and honey are common ingredients in watercolour paints, it is proposed that the surface exudate is the result of an unstable paint formulation. This formulation probably incorporated both watercolour and oil paint in an unstable emulsified state. This has resulted in the separation of the water soluble gum component from the oil paint component. Consequently, the more hydrophilic gum component has formed as a surface exudate at the air/paint interface.
The surface of Reclining Nude had accumulated a disfiguring quantity of imbibed gray dirt. This layer of dirt was especially noticeable in areas of light-colored impasto and on areas of exposed white ground. Even where the dirt was less noticeable in the darker passages of the painting, it affected the tonal balance of the painting as a whole, and dulled the subtle nuances of color.
As the dirt layer could no longer be removed by dry cleaning methods, it was decided that initial testing for a cleaning formulation should start with aqueous methods. After testing, it was determined that an aqueous mixture incorporating a weak chelating agent was effective in removing this dirt layer.
A different approach was required to treat those areas of paint identified as possessing a gum component and therefore likely to be water sensitive. A small amount of the previously-used aqueous mixture was emulsified into a larger portion of nonaromatic hydrocarbon solvent in order to clean the localized
water-sensitive areas. This emulsion was used successfully to remove the layer of dirt from the areas of paint where the gum exudate was present.
Through the use of the aqueous-based cleaning methods, the grimy appearance of the painting’s surface was considerably reduced. However, a slight overall grayish appearance remained. Other areas of discoloration included numerous drip marks and small specks of a brownish accretion, as well as further dirt trapped in the impasto of the figure and lower drapery. None of the previously-tested solutions were effective in removing any of these discolored surface materials.
Analysis of cross-sections provided further information about the remaining surface grime. It was concluded that the overall grayish appearance was the result of a wax-based coating material most likely applied in the 1950s or 1960s by a commercial gallery prior to sale. This coating effectively changed the painting’s surface appearance from matt and gloss to a uniform sheen.
Further testing established that a solvent gel was effective in removing the remaining wax-based material. The last phase of technical investigation allowed the treatment of the painting to be completed and enabled a more complete understanding of the status of all materials, both original and non-original, to be reached.
Philip Klausmeyer (philipklausmeyer@worcesterart.org) is the Andrew W. Mellon conservator in paintings and conservation science and Morwenna Blewett the Andrew W. Mellon fellow in paintings conservation, at the Worcester Art Museum.
PDF version of this abstract available here.
Important copyright information
This poster abstract was presented at the IIC congress The Object in Context: Crossing Conservation Boundaries in Munich, 2006. The text was first published in the IIC 2006 congress preceedings. The permission to publish this abstract on the INCCA website has kindly been given by the IIC. This abstract may only be downloaded for personal use. It may not be redistributed. Permission for redistribution must be requested from IIC.