View of the exhibition Gauguin: Portraits, showing Gauguin's sculpture Portrait of Meijer de Haan,  c. 1889–90. Waxed distemper paint and metallic oil paint on oak, 58.4 × 29.8 × 22.8 cm. Purchased 1968. National Gallery of Canada, Ottawa. Photo: NGC

Gauguin’s Bust of Meijer de Haan: Uncovering Groundbreaking New Knowledge

Although the works by French artist Paul Gauguin have been studied extensively, limited technical research has been devoted to his polychromed wooden sculptures and relief panels. The material of many of these works is simply described as “wood”, despite the clear presence of paint and/or other surface coatings. Until recently the National Gallery of Canada’s bust Portrait of Meijer de Haan, a masterpiece that inspired the Gallery's current exhibition Gauguin: Portraits, has been described as "polychromed oak". But what does this really mean beyond indicating that it is painted wood? What are the actual materials and techniques that Gauguin used?

To answer these questions and many related ones, a systematic in-depth examination of the bust of Meijer de Haan and a series of complex material analyses were required. The ensuing technical research was carried out over a period of four years and included a comparative study of twenty sculptural works by Gauguin. The Gallery's sculpture was examined under low and high magnification as well as various light sources. The investigation also included a variety of instrumental analyses, such as scanning electron microscopy-energy dispersive spectroscopy, infrared and Raman spectroscopy, polarized light microscopy, gas chromatography-mass spectroscopy and infrared mapping.

Part of the 360 degree rotation of Gauguin's portrait bust of Meijer de Haan. Image: NGC

The larger than life-size bust, created by Gauguin in 1889–90, depicts the Dutch artist Meijer de Haan, with whom he worked in Brittany in 1889 and whom he also portrayed in several paintings and drawings during the same period. Rather than capturing an accurate portrait, Gauguin concerned himself primarily with symbolic and emotional aspects in portraiture, rather than mere likeness.  

The analytical results and far-reaching findings of this research project brought to light some surprising, fresh aspects, knowledge and understanding of Gauguin’s materials and working techniques as they relate to the Gallery's portrait bust. The comparative study of Gauguin's wooden sculptures and relief panels in North American and European public and private collections allowed to draw parallels between our bust and the painted surface finishes on these works, as they displayed similar characteristics and associated paint losses.

Detail of paint over the bust's charred wood, as seen under magnification. Image: NGC

The visual examination proved highly informative and revealed extraordinary findings from which much could be deduced and explained. Much of the supporting evidence is barely perceptible to the naked eye, while others are only visible through magnification or viewing with light sources from along the light spectrum – ultra-violet to visible to infrared. Wood identification allowed to further classify the specie. The log Gauguin used turns out to be white oak, a tree abundant in Brittany and an extraordinarily hard wood to carve.

Among the findings was the discovery of the presence of paint on the vertical face along the top edge of the major split on the left side of the bust that indicates the wood was already split at the time Gauguin painted the bust. Furthermore, the log shows charring, most noticeably along the same side. A minute amount of unaltered paint found on the carbonized wood (visible only under magnification) indicates that the artist used a log that was partially burned. In addition paint was also found over slightly decaying wood and minor insect damage in the lower regions of the bust. With this we can conclude that he used a salvaged, split, partly deteriorated and burnt piece of wood to sculpt the bust. This is remarkable as there is no other known work of this nature by Gauguin. 

Major split in the wood on the left side of the bust;  Close-up view of paint on the vertical face of the split. Image: NGC

The instrumental analyses identified the pigments that provided a first comparison to his known oil paint pallet. They also supplied much needed information to assess the light sensitivity of the pigments to adjust, if necessary, preventive care measures. Gauguin painted distinct areas of the bust with colours that can be grouped into yellow, red, green and blue. The major pigment components of these colours were identified as yellow and red iron oxide, bone black, Prussian blue, chrome yellow and vermillion.

The light fastness of these pigments is classified as either permanent or very stable, which means they are unaffected by light, except for chrome yellow (a lead-based pigment) and vermilion (a pigment based on mercuric sulfide). Although these two pigments are considered to have good light fastness, they can darken when exposed to air or light. Due to their toxicity both chrome yellow (widely used since the early 19th century) and vermilion (in use since antiquity) have been largely replaced with cadmium yellow and cadmium red by the 1920s. In the late 19th century, however, they were still widely used not only by Gauguin but also by his contemporaries such as Vincent van Gogh and Paul Cézanne. Gauguin often highlighted details in his sculptural works with metallic paint. The Meijer de Haan bust is no exception with the application of gold-like paint to the hair and the snake-like form on his forehead. Analyses showed that fine brass particles (a copper-zinc alloy) is the major component of the paint.

Outer images: Close-up views of red, blue, green and yellow paint. Photo: NGC.  Interior images: Microscopic cross-section views of the red,blue, green and yellow paint. © Government of Canada, Canadian Conservation Institute.

While these analyses provided great insight into Gauguin’s choice of pigments, the most important and truly remarkable findings are related to the identification of the medium and the surface coating. In order to define a type of paint, the medium – the vehicle for binding the pigments together into a paint – must be known. Although this type of analysis is usually straightforward, surprisingly the identification of the bust's medium turned out to be a challenge and initial results were unclear or simply not forthcoming. Wax was the only material that was detected in the various paint samples. In the absence of any other binding agent, one may have concluded that it is encaustic paint. The characteristics of this paint, however, did not align with a wax-based paint, especially considering the powdery appearance and the predominant presence of calcium carbonate (chalk), and calcium sulfate dihydrate (gypsum/plaster) in each sample. Even if only in small quantities, there had to be a binder present, such as oil or, more likely, an animal glue. A more complex series of analyses, combined with chemical manipulation of the samples, finally revealed the hidden presence of a protein. This was a major breakthrough which allowed us to identify the paint as Soft Distemper, a paint primarily composed of chalk, raw pigments and animal glue.

This find is momentous, as this is the first time that distemper has been identified on one of Gauguin’s wooden carvings. It is groundbreaking new knowledge and adds a further dimension to our knowledge of Gauguin’s known paint materials. Of further significance is the conclusion that, based on the comparative study of his works made between 1889 and 1890, Gauguin likely used distemper paint on other wooden sculptural works he created during this period.

Finally, cross-section analyses and ATR mapping (attenuated total reflectance micro-spectroscopy) of the paint samples confirmed wax (previously identified as beeswax) to be present on the surface only, with limited penetration into the opaque, powdery, matt paint layer. With this we can conclude that Gauguin used beeswax instead of a varnish as a surface coating to saturate the colours and impart a low sheen to the surface.

View of interactive 360 degree rotation screen, with "hotspot" activation points. Photo: NGC

As part of the Gallery's Gauguin: Portraits exhibition, a special display dedicated solely to these findings allows visitors to explore the results through succinct panel texts. While Gauguin’s masterpiece can only be viewed through a glass vitrine, a full-size replica, made from a 3D scan, is fully accessible to visitors who are invited to touch the copy and explore the bust’s forms and its intricate surface texture. Alongside, an interactive screen offers the opportunity to explore the sculpture visually in 360-degree rotation by activating eight "hotspots" that dive into details, showing rare views such as the bust’s top and underside, Gauguin’s brush strokes and pigment particles within his paint. For further insights, a video in the adjacent room speaks to the exhibition and the journey into its creation, as well as to the various aspects of the technical research.

Thanks go to the Canadian Conservation Institute in Ottawa and to Canada's national synchrotron light source facility in Saskatoon (Canadian Light Source Inc.) for their work and participation in this research project.

Gallery view of special display on the scientific findings. Photo: NGC

 

Gauguin: Portraits is on view at the National Gallery of Canada until September 8, 2019, before travelling to the National Gallery in London (October 7, 2019 to January 26, 2020). For lectures, talks and related activities, see the Gallery's extensive public program. Share this article and subscribe to our newsletters to stay up-to-date on the latest articles, Gallery exhibitions, news and events, and to learn more about art in Canada.

Gauguin: Portraits - The Experience

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