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14 february 2011 |
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Press Release in English - Persbericht in het Nederlands - Communiqué
de Presse en Français |
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X-Rays show why van
Gogh paintings
lose their shine |
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– The mystery of the discolored Van Goghs
(Los Angeles Times, 14/02/2011) – – Why Van Gogh is entering his brown period … (The Independent,
15/02/2011) – – Van Gogh doomed his sunflowers by adding white pigments to yellow
... (The Guardian, 15/02/2011) – – Scientists solve mystery of Van Gogh's colours changing hue (The Sydney Morning Herald, 16/02/2011)
– – Fade to Brown? Van Gogh's Sunflowers Are Changing Color From
Sunlight (Time, 16/02/2011) – – X-rays show why van Gogh paintings lose their luster. (Deutsche Welle, 16/02/2011) – Scientists
have identified a complex chemical reaction responsible for the degradation
of two paintings by Vincent van Gogh and other artists of the late 19th
century. This discovery is a first step to understanding how to stop the
bright yellow colours of van Gogh’s most famous
paintings from being covered by a brown shade, and fading over time. In the
meantime, the results suggest shielding affected paintings as much as
possible from UV and sunlight. The results are published online on 14
February 2011 in the journal Analytical
Chemistry of the American Chemical Society. The
work was carried out by an international team of scientists from four
countries led by Koen Janssens of Antwerp University (Belgium), with Letizia
Monico, an Italian chemist preparing a Ph.D. at Perugia University (Italy) and Antwerp University,
taking the centre stage in the experiments. As an Erasmus student, she worked
for one year in Janssens’ research group in Antwerp, and is also the lead
author of the two papers. Scientists from the CNR Institute of Molecular Science and Technologies (Perugia,
Italy), the CNRS C2RMF (Paris, France), TU Delft (Netherlands) and the van
Gogh Museum (Amsterdam, Netherlands) were also part of the team. Some of the
samples were made available by RCE (formerly ICN), Netherlands. Uncovering
the secrets of the chemical reaction needed deployment of an impressive arsenal
of analytical tools, with synchrotron X-rays at the ESRF in Grenoble (France)
providing the final answers. “For every
Italian, conservation of masterpieces has always mattered. I am pleased that
science has now added a piece to a puzzle that is a big headache for so many
museums” says Letizia Monico from University of Perugia. The
experiment reads like a crime scene investigation. The scientists employed an
X-ray beam of microscopic dimensions to reveal a complex chemical reaction
taking place in the incredibly thin layer where the paint meets the varnish.
Sunlight can penetrate only a few micrometers into the paint, but over this
short distance, it will trigger a hitherto unknown chemical reaction turning
chrome yellow into brown pigments, altering the original composition. Van
Gogh’s decision to use novel bright colours in his
paintings is a major milestone in the history of art. He deliberately chose colours that conveyed mood and emotion, rather than
employing them realistically. At the time, this was completely unheard of
and, without major innovations in pigment manufacturing made in the 19th
century, would also have been impossible. It
was the vibrancy of new industrial pigments such as chrome yellow which
allowed van Gogh to achieve the intensity of, for example, his series of
Sunflowers paintings. He started to paint in these bright colours
after leaving his native Holland for France where he became friends with
artists who shared his new ideas about the use of colours.
For one of them, Paul Gauguin, he started painting yellow sunflower motifs as
a decoration for his bedroom. The
fact that yellow
chrome paint darkens under sunlight has been known since the early 19th
Century. However, not all period paintings are affected, nor does it always
happen at the same speed. A recently documented case in point is briefly
discussed at the website
of the Van Gogh Museum (Amsterdam) by Ella Hendriks who, in October 2010,
remarked “I had problems with matching the elusive chrome yellow colour of the foot end of the bed with its aged greenish-brown translucent skin.”
while describing the restoration of Van Gogh’s “The
Bedroom” (1888).
As chrome yellow is toxic,
artists quickly switched to new alternatives in the 1950s. However, Vincent
van Gogh did not have this choice, and to preserve his work and that of many
contemporaries, interest in the darkening of chrome yellow is now rising
again. To solve a chemical puzzle
nearly 200 years old, the team around Janssens used a two-step approach:
first, they collected samples from three left-over historic paint tubes.
After these samples had been artificially aged for 500 hours using an
UV-lamp, only one sample, from a paint tube belonging to the Flemish Fauvist
Rik Wouters (1882-1913), showed significant darkening. Within 3 weeks, its
surface of originally bright yellow had become chocolate brown. This sample
was taken as the best candidate for having undergone the fatal chemical
reaction, and sophisticated X-ray analysis identified the darkening of the
top layer as linked to a reduction of the chromium in the chrome yellow from Cr(VI) to Cr(III). The scientists also reproduced Wouters’
chrome yellow paint and found that the darkening effect could be provoked by
UV light. In the second step, the
scientists used the same methods to examine samples from affected areas of
two van Gogh paintings, View of Arles
with Irises (1888) and Bank of the
Seine (1887), both on display in the Van Gogh Museum in Amsterdam. “This type of cutting edge research is crucial to advance our
understanding of how paintings age and should be conserved for future
generations”, says Ella Hendriks of the van Gogh Museum Amsterdam. Because the affected areas in
these multicoloured samples were even more
difficult to locate than in the artificially aged ones, an impressive array
of analytical tools had to be deployed which required the samples travelling
to laboratories across Europe. The results indicate that the reduction
reaction from Cr(VI) to Cr(III) is likely to also
have taken place in the two van Gogh paintings. The microscopic X-ray beam
also showed that Cr(III) was especially prominent in
the presence of chemical compounds which contained barium and sulphur. Based on this observation, the scientists
speculate that van Gogh’s technique of blending white and yellow paint might
be the cause of the darkening of his yellow paint. “Our next experiments are already in the pipeline. Obviously, we want
to understand which conditions favour the reduction
of chromium, and whether there is any hope to revert pigments to the original
state in paintings where it is already taking place.”, summarises Koen Janssens from University of Antwerp. Some details of the investigation. The techniques used by the
scientists in the preliminary phase included X-ray diffraction along with
various spectroscopies employing infrared
radiation, electrons and X-rays at the universities of Antwerp and Perugia,
and at two synchrotrons (ESRF and DESY). “I am not aware of a similarly big effort ever having been made for
the chemistry of an oil painting”, says Joris Dik, Professor at Delft
Technical University. In the decisive step, two
techniques were combined using a single X-ray beam at the ESRF: X-Ray
fluorescence (XRF) and X-Ray absorption near-edge spectroscopy (XANES). For
the XRF, the microscopic beam size (0.9 x 0.25 µm²) made possible to separate
the study of degraded and unaffected areas, and the XANES technique proved
the speciation of chromium, i.e. the reduction from Cr(VI)
to Cr(III). "Our
X-ray beam is one hundred times thinner than a human hair, and it reveals
subtle chemical processes over equally minuscule areas. Making this possible
has opened the door to a whole new world of discovery for art historians and
conservators,” says
Marine Cotte, an ESRF scientist also working at CNRS/C2RMF (Musée du Louvre). The reduction of chromium
that had been observed in the artificially aged sample from the atelier of
Rik Wouters was finally confirmed in both microsamples
from the van Gogh paintings. The study was completed with
a nanoscopic investigation of the discoloured paint using high-resolution electron energy
loss spectroscopy (EELS) at the EMAT Centre of the University of Antwerp,
which confirmed the results and showed that the newly formed Cr(III) compounds were formed as a nanometer-thin coating
of the pigment particles that constitute the paint. Reference: L. Monico
et al., Degradation Process of Lead Chromate in Paintings by Vincent van Gogh
Studied by Means of Synchrotron X-ray Spectromicroscopy
and Related Methods. 1. Artificially Aged Model Samples and 2. Original Paint
Layer Samples, Analytical Chemistry
15 February 2011. Monico, Hendriks, Dik, Cotte and Janssens are authors of
the paper. Monico is the lead author. The research was supported by the
University of Perugia (Perugia, Italy), CNR di Scienze e Tecnologie Molecolari CNR-ISTM (Perugia, Italy), Universiteit
van Antwerpen (Antwerp, Belgium), Delft University of
Technology (Delft, Netherlands), Centre de Recherche
et de Restauration des Musées
de France, CNRS UMR171 (Paris, France), van Gogh Museum (Amsterdam,
Netherlands), and European Synchrotron
Radiation Facility ESRF (Grenoble, France).
Media contacts: ESRF, Claus Habfast, claus.habfast@esrf.fr +33 4 7688 2128
and +33 666 662 384 University of Antwerp, Peter de Meyer, Peter.DeMeyer@ua.ac.be +32 3 265 47 11 CNR, Marco Ferrazzoli, marco.ferrazzoli@cnr.it +39 06 4993 3383
CNRS, Laetitia Louis-Hommani, presse@cnrs-dir.fr +33 1 44 96 51 37 TU Delft, Michel van Baal, , M.vanBaal@tudelft.nl +31 15 278 5454 Van Gogh Museum, Janine Fluyt, Fluyt@vangoghmuseum.nl, +31 20 57 05 221 Science contacts: |
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University of Antwerp, Prof. Koen Janssens, koen.janssens@ua.ac.be; Dr. Jo
Verbeeck, jo.verbeeck@ua.ac.be University of Perugia & CNR,
Prof. Costanza Miliani, miliani@thch.unipg.it,
Letizia Monico, letizia.monico@gmail.com TU Delft, Prof. Joris Dik, j.dik@tudelft.nl Van Gogh Museum & RCE, Dr. Ella Hendriks, hendriks@vangoghmuseum.nl; Dr.
Muriel Geldof, M.Geldof@cultureelerfgoed.nl ESRF & CNRS,
Dr. Marine Cotte, marine.cotte@esrf.fr
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Attention in the media (click on the logos shown below):
(De Standaard, Brussels,
15/2/2011) (De Volkskrant, Amsterdam, 15/2/2011)
(NRC
Handelsblad, Amsterdam, 15/2/2011)
64500
on 14 february 2011)
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1 August 2008 |
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PRESS
RELEASE - Persbericht in het Nederlands |
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Looking
through Van Gogh |
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Advanced
X-ray analysis reveals a portrait below the painting of a landscape |
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Behind this
painting is the portrait of a woman. |
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It is well-known that Vincent van Gogh often painted over his older works. Experts estimate that about thirty percent of his paintings conceal other compositions under them. A new technique, based on synchrotron radiation induced X-ray fluorescence spectroscopy, reveals this type of hidden painting. |
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The techniques usually
employed to reveal concealed layers of paintings, such as conventional X-ray
radiography and Infra-red reflectography, have
their limitations. Together with experts from the Deutsches
Elektronen-Synchrotron in Hamburg and the Kröller-Müller Museum, TU Delft materials expert and art
historian Dr Joris Dik and University of Antwerp chemistry professor Koen
Janssens therefore chose to adopt a different approach. The painting is
subjected to an X-ray beam from a synchrotron radiation source, and the fluorescence
of the layers of paint is measured. This technique has the major advantage
that the measured fluorescence is specific to each chemical element. Each
type of atom (e.g. lead or mercury) and also individual paint pigments can
therefore be charted individually. The benefit of using synchrotron radiation
of high energy is that it is strongly penetrating so that element specific
analysis well below the visible surface becomes possible. The upper layers of
paint distort the measurements only to a small degree. Moreover, the speed of
measurement is high, which allows relatively large areas to be visualised. |
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The measurements enabled researchers to reconstruct the
concealed painting in unparalleled detail. In particular the combination of
the distribution of the elements mercury and antimony (from specific paint
pigments) provided a ‘colour photo’ of the portrait
which had been painted over. |
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Press
release by TU Delft, NL |
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Contact
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Links to Reactions in worldwide press and media (30 July - 2 August 2008)
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In the morning
of 31 July 2008, the "Hidden Van Gogh revealed" news story was
featured as one of the central items on the main page of Yahoo. Among the
list of "Most view photo's" on that day
were 3 pictures from the scanning experiment. |
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Both synchrotron facilities at which the
investigations took place,
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Articles in the general press. Click on a logo to follow the
corresponding link.
2 early articles (30 July 2008) in the Flemish press
(.PDF, in Dutch)TV coverage (30 July 2008) in Belgium (VTM)
Interview with K. Janssens (Univ. of Antwerp)
(23 MB, .MOV, in Dutch)
TV coverage (30 July 2008) in Belgium(ATV)
Interview with K. Janssens (Univ. of Antwerp)
(13 MB, .MOV, in Dutch)TV coverage (30 July 2008) in The Netherlands (NOS)
Interview with J. Dik (TUDelft) and L. Van der Loeff
(Kröller-Müller Museum) (8 MB, .MOV, in Dutch)
TV coverage (30 July 2008) in The Netherlands (RTL4)
Interview with J. Dik (TUDelft) and L. Jansen (Van Gogh Museum Amsterdam) (28 MB, .MOV, in Dutch)
Listen to a France-Info radio interview
with Marine Cotte and Joris Dik
('Un Van Gogh peut en cacher un autre', 31 July 2008,
in French)
TV coverage (2 August 2008) in Japan
(0.8 MB, .MOV, in Japanese)Listen to an NPR radio interview with Koen Janssens or
Watch an NPR video with commentary by Joris Dik
(both from 'All Things Considered', 2 August 2008,
in English)Listen to a Radio Suisse Romande interview
with Marine Cotte
('Le tableau caché de Van Gogh', 2 September 2008,
in French)TV coverage (11 September 2008) in Germany (RTL Nord)
"Das Rätsel der versteckter Bilder von Vincent Van Gogh"
with J. Dik (TUDelft) and L. Van der Loeff (Kröller-Müller Museum),
K. Rickers, W. Drube (DESY) and K. Janssens (UAntwerp)
(52 MB, .MOV, in German)
+ the opinion of several Dutch art experts (in Dutch)
xxx
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Click here for a more complete list (up to 3 August 2008, 2 pm), compiled by W. Drube, DESY.
(number of page hits since 31 July 2008;
counter reached 10000 hits on 2 August 2008, 20000 on 4 August 2008;
64500 on 14 february 2011)
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