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7 - Conservation of the Amsterdam Sunflowers: From Past to Future
- Edited by Muriel Geldof, Maarten van Bommel, Marije Vellekoop, Ella Hendriks
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- Book:
- Van Gogh's Sunflowers Illuminated
- Published by:
- Amsterdam University Press
- Published online:
- 25 November 2020
- Print publication:
- 21 June 2019, pp 175-206
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Summary
Introduction
This chapter lays out a conservation timeline, from past to future, for the Amsterdam version of Van Gogh's Sunflowers. It starts by considering the restoration history of the painting in order to assess its current physical state, and looks ahead to formulate an appropriate strategy for future conservation treatment and display. Due attention is paid to the two recorded episodes of restoration performed in 1927 and 1961 by the Dutch restorer, Jan Cornelis Traas. Based on physical and chemical investigation of Sunflowers we attempt to reconstruct what these former treatments (which are barely documented) entailed and consider the repercussions for the present condition of the painting. The former interventions by Traas also serve as a benchmark to reflect on current choices made, highlighting the extent to which ideas and methodologies have continued to evolve over the past century as conservation has moved further away from being a singularly craft-based activity to become an established historical and scientific discipline underpinned by ethical guidelines.
Jan Cornelis Traas (1898–1984)
As mentioned, the two main recorded interventions to the Amsterdam Sunflowers may be associated with the Dutch restorer, Jan Cornelis Traas, who treated the picture in 1927, close to the start of his career, and again in 1961, shortly before he retired. Traas was the first restorer to be appointed at the Mauritshuis in The Hague where he worked from 1931 to 1962 and treated hundreds of paintings, including iconic masterpieces such as Girl with a Pearl Earring by Johannes Vermeer. Yet despite the magnitude and importance of his restoration oeuvre, J.C. Traas (as he is usually referred to in surviving documents), has remained somewhat obscure. He is shown here in the only known surviving photograph of him at work, shortly before he retired (fig. 7.1). Unlike his illustrious contemporaries, A. Martin de Wild (1899–1969) and Helmut Ruhemann (1891–1973), for example, Traas did not publish anything, he appears to have kept no records of his work and no personal archive is known. However, the study of some newly discovered historical documents, combined with physical examination of Sunflowers and a large number of other works he treated, allows us to recover an idea of his working practices and approaches viewed within the context of his day.
6 - Structure and Chemical Composition of the Surface Layers in the Amsterdam Sunflowers
- Edited by Muriel Geldof, Maarten van Bommel, Marije Vellekoop, Ella Hendriks
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- Book:
- Van Gogh's Sunflowers Illuminated
- Published by:
- Amsterdam University Press
- Published online:
- 25 November 2020
- Print publication:
- 21 June 2019, pp 159-174
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- Chapter
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Summary
Introduction
Since its completion by Vincent van Gogh, the Amsterdam Sunflowers has been the subject of a complex history of interventions. Combined with the natural ageing and deterioration of the materials used by the artist, this has strongly affected the present appearance of the painting. The materials and techniques used in Sunflowers and related colour changes have been presented in chapters 4 and 5. This chapter focuses on characterizing the non-original surface layers present as well as secondary compounds arising from pigment-binder interaction in original paint components. The outcomes of this research help to reconstruct the restoration history of the painting and to understand its present condition, as a basis for optimizing future conservation treatment (as elaborated in chapter 7).
In keeping with Van Gogh's usual practice in the period, he left Sunflowers in an unvarnished state. Today, however, multiple layers of varnish are present. These have yellowed and make the painting appear highly glossy, whereas originally it presumably had the more subtle satin gloss related to pure oil paint. Conversely, some areas of the painting now look matt, since wax has been locally applied in the past.
Historical records provide sparse information regarding the surface layers added during earlier campaigns of treatment (see chapter 7). We know that the painting was varnished in 1927 by the conservator Jan Cornelis Traas, as part of a broader restoration and structural (lining) treatment. Remains of paper tape on the tacking margins of the painting are believed to date from this period (see chapter 7, p. 184). Further documents record that in 1961, Traas worked on the painting again. However, as there is no known account of what this treatment entailed, it remained in question whether Traas removed the 1927 varnish and/or applied new surface coating layers instead. Furthermore, in the late twentieth century, wax was applied in certain areas, used to matt down the glossy varnish and/or impregnate and consolidate the ground.
This chapter describes the outcome of the technical examinations of the Amsterdam Sunflowers, characterizing the surface layers present and assessing the history of application as revealed by their stratigraphy and chemical composition.
8 - Methods and Techniques: Optical Coherence Tomography (OCT)
- Edited by Muriel Geldof, Maarten van Bommel, Marije Vellekoop, Ella Hendriks
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- Book:
- Van Gogh's Sunflowers Illuminated
- Published by:
- Amsterdam University Press
- Published online:
- 25 November 2020
- Print publication:
- 21 June 2019, pp 207-227
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Summary
Optical coherence tomography (OCT) is an imaging technique offering a non-invasive alternative to the traditional analysis of artworks by means of sampling. A cross-section photomicrograph of a sample collected from a painting has its own limitations, mostly due to the restricted number of samples it is possible to collect. There is a need, therefore, for non-invasive verification of locally acquired data, even at the price of not attaining the fuller information given by sample examination. OCT offers such an opportunity, as a non-invasive, fast and contactless technique that provides cross-sectional images of sub-surface structures over relatively large areas. OCT has been used for the examination of artworks since 2004, but recent progress in imaging techniques has made it more applicable to resolving practical issues raised by art conservators and curators. While most applications are connected with the examination of transparent and semi-transparent layers on easel paintings, other objects, such as wall paintings, historic and archaeological glass, ceramics, semi-precious stones like jade, and even parchment, have also been successfully examined using OCT.
A major limitation of OCT for the examination of artworks is the limited transparency of their structure to the probing light utilized by the technique. OCT is an interferometric technique that uses broadband infrared radiation to determine the distance to a structure that scatters or reflects light. If the spectrum of the source is broad enough (c. 200 nm in near infrared) the precision of layer thickness measurements (the axial resolution of technique) is about 3 μm in air and 2 μm in media such as varnish. This permits detection of thin transparent layers, for example varnishes on the surface of a painting. The unique instrument used to examine the Amsterdam Sunflowers was constructed at Nicolaus Copernicus University in Toruń especially for the examination of artworks within the EU CHARISMA project. It utilizes a superluminescent light source with a spectral range of 770–970 nm. The total power measured at the object is less than 0.8 mW and the beam is never focused at the same spot for longer than 50 μs. The narrow beam of infrared light penetrates the object as far as is possible for a given absorbance of the structures at this spot – usually a fraction of a millimetre – and is collected by the instrument's optics.