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Press Release in English - Persbericht in het Nederlands -
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LED lights may be bad for Van Gogh Paintings |
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Possibly dozens of masterpieces sensitive to darkening of yellow areas An international team of scientists has used synchrotron X-rays to better understand why some bright yellow colours in Vincent Van Gogh’s paintings with time are turning brown, while others do not. The research focus was on chrome yellow, favoured by Van Gogh to depict sunshine and light, several types of which were found to be very sensitive to darkening under green and blue light. The scientists recommend that museums identify all paintings with this type of chrome yellow, and protect them in particular from the increasingly popular LED lights as these emit a large amount of blue. The scientific results of the scientists have been published on 14 November 2012 in two papers in the journal Analytical Chemistry. There form Part 3 and Part 4 of a series of studies on this topic. Previously the same group of researchers from Italy, Belgium, Netherlands, France and Germany had discovered that especially the light yellow tones in Van Gogh’s paintings are prone to darkening and that this process involves a chemical reduction of chromium, the key element in the chrome yellow pigment. A reduction is the opposite of an oxidation reaction. However, they did not understand the origin of this chemical transformation, and why the degradation differed considerably among paintings. State-of-the-art X-ray analysis of an extensive series of Van Gogh paintings belonging to 3 musea in The Netherlands and France allowed the researchers to conclude that Van Gogh did not always use the same type of chrome yellow paint. To confirm these findings, also original paints employed by Van Gogh and by Cézanne in the late 19th century were investigated. The key experiments, involving speck-sized paint fragments of the Van Gogh paintings, were performed at two synchrotron facilities, ESRF in Grenoble (France) and DESY in Hamburg (Germany), and in cultural heritage labs in Italy and The Netherlands. Next to regular lead chromate, aka "Middle yellow", that chemically is quite stable, Van Gogh also liked to use "Lemon yellow" and "Primrose yellow". Some of the 'non-regular' types turned out to be fairly reactive under light as they have a different crystal structure and/or a higher sulfate content. The more sulfur is present in a chrome yellow pigment, the more unstable it becomes. In laboratory tests with different samples of chrome yellow paint, those containing the unstable varieties turned brownish/olive green after just a few days of exposure to green-blue light. Regular chrome yellow maintained its colour, also when irradiated with the more damaging UV light and during longer periods.
Figure caption: Light-sensitive lead chromate before (leftmost picture) and after aging with different wavelength bands. "We have found the unstable forms of chrome yellow in several well-known paintings, such as 'Portrait of Gauguin' and the famous 'Vase with Sunflowers' of the Van Gogh museum in Amsterdam", says Letizia Monico, a Chemistry PhD student in Perugia (Italy) and Antwerp (Belgium) who is the central person in this investigation.
Figure caption: "Portrait of Gauguin" (aka "Man with Red Beret") by Vincent Van Gogh (Van Gogh Museum, Amsterdam).
Figure Caption: Colour photograph (embedded and polished cross-section) of a minuscule paint fragment from "Portrait of Gauguin", that proved to contain unstable variants of lead chromate. "As we are aware that both stable and unstable forms of chrome yellow paint were used not only by Vincent Van Gogh but also by Paul Cézanne, we advise musea that own such masterpieces to ascertain whether the unstable forms of chrome yellow were used and if needed to tailor their lighting systems accordingly," summarizes Koen Janssens from the University of Antwerp who coordinated the work of the team. Costanza Miliani (CNR, Italy) points out that "we were surprised to note that already under conditions of illumination currently considered safe, some of our test samples started changing colour quite quickly". Bruno Brunetti (Univ. of Perugia) adds "We could show that by means of relatively simple equipment based on reflection of infra-red light, that may be operated in the museum galleries themselves, it is possible to establish which type of chrome yellow is present in a painting." Ella Hendriks, Head of Conservation at the Van Gogh Museum in Amsterdam concludes: "Studies like these are very important to make museum curators aware that, even under ambient light conditions, the degradation of some sensitive materials proceeds continuously. Musea should carefully consider the potential impact of, for example, the new, LED-based, lighting systems that are now being installed in collections."
Emission spectrum of a typical "white" LED, containing a substantial portion of harmful blue light. Source: http://www.lightemittingdiodes.org.
Press contacts University of Antwerp, Peter De Meyer, telephone + 32 3 265 47 11 or peter.demeyer@ua.ac.be Scientific contacts
University of Antwerp,
Prof. Koen Janssens, koen.janssens@ua.ac.be; University of Perugia & CNR,
Prof. Bruno Brunetti, brubo@dyn.unipg.it, Prof. Costanza Miliani, miliani@thch.unipg.it,
Dr. Letizia Monico, letizia.monico@gmail.com
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
DESY,
Dr. Gerald Falkenberg, gerald.falkenberg@desy.de
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Media links 4-7 January 2013
Kranten- en webartikels in het Nederlands De Standaard http://www.standaard.be/artikel/detail.aspx?artikelid=DMF20130103_00421588 Het Laatste Nieuws http://www.hln.be/hln/nl/961/Wetenschap/article/detail/1557172/2013/01/04/LED-verlichting-kan-schilderijen-beschadigen.dhtml NRC Handelsblad (berichtgeving dd. 21/12/12) http://www.internetgazet.be/led-lampen-kunnen-schilderijen-beschadigen.aspx http://article.wn.com/view/WNAT7cee261cff65f5d115d00d793f0509a0 http://www.kunstbeeld.nl/nl/nieuws/20076/led-verlichting-tast-schilderijen-aan.html http://www.facebook.com/UniversiteitAntwerpen/posts/185851938224182 http://nieuws.be.msn.com/binnenland/led-verlichting-kan-schilderijen-beschadigen http://binnenland.nieuws.nl/733664/ledverlichting_kan_museale_werken_aantasten http://frontpage.fok.nl/nieuws/579611/1/1/100/ledverlichting-kan-museale-werken-aantasten.html http://historiek.net/nieuws/algemeen/7687-blauw-led-licht-kan-oude-schilderijen-beschadigen http://www.artlistings.nl/kunstnieuws/3391-led-verlichting-schadelijk-voor-schilderijen
Trick film auf Deutsch Spiegel On-line http://www.spiegel.de/wissenschaft/mensch/led-licht-schadet-gelbtoenen-auf-van-gogh-gemaelden-a-875531.html
http://www.youtube.com/watch?v=VvuPSWT6B_8 http://nachrichten.t-online.de/ursache-fuer-verfaerbte-gemaelde-gefunden/id_61557630/index http://www.desy.de/aktuelles/@@news-view?id=4381&lang=ger
News articles in English Financial Times Magazine http://www.ft.com/cms/s/2/dc33fa94-4bd6-11e2-887b-00144feab49a.html#axzz2H2olJoJ5 http://www.onenewspage.co.uk/n/Science/74vnp5ka0/Lights-off-for-Van-Gogh.htm http://www.deredactie.be/cm/vrtnieuws.english/flanders%2Btoday/130104_LED_paintings http://www.expatica.com/be/news/belgian-news/LED-bulbs-can-damage-paintings_254594.html http://www.esrf.eu/news/general/led-lights-bad-for-chrome-yellow/index_html/
Articles en français
Émission de Télévision RTBF Journal Televisé http://www.rtbf.be/info/societe/detail_l-eclairage-a-l-aide-de-lampes-led-peut-endommager-les-toiles-des-grands-maitres?id=7901658
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14 september 2012 - Press Release in English - Persbericht in het Nederlands -
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X-rays unravel mysterious degradation of a van Gogh painting |
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(left) Photo of the painting “Flowers in a blue vase” painted by Vincent Van Gogh in 1887. The part affected by the discolouration is in the upper right. Credit Kröller-Müller Museum.
Discolouration With a sophisticated X-ray analysis scientists have identified why parts of the Van Gogh painting "Flowers in a blue vase" have changed colour over time: a supposedly protective varnish applied after the master's death has made some bright yellow flowers turn to an orange-grey colour. The origin of this alteration is a hitherto unknown degradation process at the interface between paint and varnish, which studies at DESY's X-ray source PETRA III and at the European Synchrotron Radiation Facility ESRF in Grenoble (France) have revealed for the first time.
The results are published in an upcoming issue of "Analytical Chemistry", the first author of which is Geert Van der Snickt, who received a PhD in Conservation and Restoration from the University of Antwerp (Belgium) for this work. The research team was led by Koen Janssens from Antwerp and also comprised scientists from TU Delft (Netherlands), the French CNRS, the Kröller-Müller Museum in Otterlo (Netherlands), the ESRF and DESY. Click on the illustration below to download the entire article.
The painting Vincent Van Gogh (1853-1890) painted “Flowers in a blue vase” in 1887 in Paris, and in the early 20th century, the painting was acquired by the Kröller-Müller Museum. The master usually did not varnish his works, but this painting was later covered with a supposedly protective varnish, like many other Van Gogh paintings in the first half of the 20th century. "A conservation treatment in 2009 revealed an unusual grey opaque crust on parts of the painting with cadmium yellow paint," says paintings conservator Margje Leeuwestein from the Kröller-Müller Museum. The pigment The cadmium yellow (cadmium sulphide, CdS) used by Van Gogh was a relatively new pigment, of which it has recently been discovered that in unvarnished paintings, it oxidizes with air (to cadmium sulphate; CdSO4) making the pigments lose colour and luminosity. “We identified this process a few years ago, and the observation that instead of a slightly off-white, transparent oxidation layer, the pigments in this painting were covered with a dark, cracked crust intrigued us very much,” says Janssens. "The removal of the orange-grey crust and discoloured varnish was not possible without affecting the very fragile original cadmium yellow paint on these parts," adds Leeuwestein.
Microsamples from art masterpieces, moulded in Plexiglass blocks ready for investigation with synchrotron X-rays. The historic paint tube at the bottom is from the personal collection of M. Cotte. Credit I. Montero/ESRF.
Optical photograph of a minuscule chip of paint used during the analysis. Lower side: cadmium yellow paint retaining its original bright yellow colour; upper side: discoloured varnish layer rendered opaque by the precipitation of lead sulfate and cadmium oxalate. Credit University of Antwerp. X-ray Analysis To identify what had happened, the museum took two microscopic paint samples – each only a fraction of a millimetre in size - from the original painting and sent them to Janssens for a detailed investigation. The scientists studied the samples using powerful X-ray beams at the ESRF and at DESY's PETRA III, revealing their chemical composition and internal structure at the interface between varnish and paint.
Artists illustration of a plexiglass blockwith a paint microsample mounted for investigation in the vacuum chamber of the synchrotron X-ray microscope (beamline ID21) at ESRF. The small spot in the centre of the plexiglass block is the sample, and the cylindrical tube is the front side of the X-ray detector. Credit ESRF.
Photograph of the X-ray micro/nanoprobe (beamline P06) at the PETRA-III synchrotron of DESY where some of the X-ray analyses were performed. Credit DESY. To their surprise, they did not find the crystalline cadmium sulphate compounds that should have formed in the oxidation process. "It emerged that the sulphate anions had found a suitable reaction partner in lead ions from the varnish and had formed anglesite," explains DESY scientist Gerald Falkenberg. Anglesite (PbSO4) is an opaque compound that was found nearly everywhere throughout the varnish. "The source of the lead probably is a lead-based siccative that had been added to the varnish," adds Falkenberg.
Distributions of cadmium yellow (CdS), anglesite (PbSO4), cadmium oxalate (CdC2O4) and calcium carbonate (CdCO3) in the area indicated in the photograph (sample area A). “At the interface between paint and varnish, the cadmium ions together with degradation products from the varnish itself also formed a layer of cadmium oxalate,” says ESRF scientist Marine Cotte. Together with the anglesite, the cadmium oxalate (CdC2O4) accounts for the opaque, orange-grey crust disfiguring parts of the painting on a macroscopic level. This "ingrowth" also makes it very difficult, if not impossible to remove the varnish without damaging the paint layer below. To varnish or not to varnish ? After this discovery, conservators in many museums will have to newly address the question of restoring Van Gogh paintings. "This study on the deterioration of cadmium yellow is an excellent example of how collaboration between scientists and conservators can help to improve our understanding of the condition of Van Gogh's paintings and lead to better preservation of his works," says Ella Hendriks, Head of Conservation of the Van Gogh Museum in Amsterdam, who did not take part in the study. "Many of Van Gogh’s French period paintings have been inappropriately varnished in the past and removal of these non-original varnish layers is one of the challenges facing conservators on a world-wide basis today. The type of information provided by Janssens and his team is vital to support the difficult decisions that conservators often have to make regarding such complex cleaning treatments." Reactive chemical cocktail "Once again, we find that paintings by Vincent Van Gogh are not static entities for decades and centuries to come. Over a period of 100 years, they can actually be considered a fairly reactive cocktail of chemicals that behaves in unexpected manners”, concludes Janssens. Geert Van der Snickt adds that “especially the presence of sulphides puts the durability of the paintings at risk.” In the next four years, Janssens’ research group plans to study how museum indoor conditions and air pollution affect cadmium yellow and related sulphide-containing pigments used by artists. |
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Press contacts University of Antwerp, Peter De Meyer, telephone + 32 3 265 47 11 or peter.demeyer@ua.ac.be Scientific contacts University of Antwerp,
Dr. Geert Van Der Snickt, geert.vandersnickt@ua.ac.be ;
Prof. Koen Janssens, koen.janssens@ua.ac.be
TU Delft,
Prof. Joris Dik, j.dik@tudelft.nl
Deutsches Elektronen Synchrotron (DESY) - PETRA-III facility,
Dr. Gerald Falkenberg, gerald.falkenberg@desy.de
European Synchrotron Radiation Facility (ESRF), Dr. Marine Cotte marine.cotte@esrf.fr
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In English (International) http://www.rsc.org/chemistryworld/2012/09/helping-hand-van-gogh-conservators http://www.bbc.co.uk/news/science-environment-19597399
http://cordis.europa.eu/fetch?CALLER=EN_NEWS&ACTION=D&SESSION=&RCN=35033 http://www.livescience.com/23194-van-gogh-painting-color-change.html http://www.livescience.com/23193-van-gogh-paintings-science.html http://www.eurekalert.org/pub_releases/2012-09/esrf-xum091312.php http://www.science-news.eu/nano-materials-news/cluster175443/ http://www.physnews.com/nano-materials-news/cluster346850811/ http://thunderfeeds.com/reader/news/van-goghs-flowers-in-a-blue-vase-damage-seen-in-xrays-bbc-news http://www.esrf.eu/news/general/van-gogh-cds/index_html/ http://www.lightsources.org/cms/?pid=1005047 http://www.chemspy.com/x-rays-unravel-mysterious-degradation-of-a-van-gogh-painting.html http://earthsky.org/science-wire/x-rays-unravel-mysterious-degradation-of-a-van-gogh-painting http://www.sciencecodex.com/xrays_unravel_mysterious_degradation_of_a_van_gogh_painting-98426 http://phys.org/news/2012-09-x-rays-unravel-mysterious-degradation-vincent.html http://www.lightsources.org/cms/?pid=1005047 http://www.sciencedaily.com/releases/2012/09/120914080908.htm http://www.kmm.nl/news/334/Schilderij-Van-Gogh-onderwerp-van-onderzoek http://www2.cnrs.fr/presse/communique/2775.htm?&theme1=5 http://www.sciencenewsline.com/summary/2012091415020005.html http://regator.com/p/257517601/x-rays_uncover_the_mysterious_degradation_of_van_gogh/ http://www.allvoices.com/tags/grey-colours http://www.i4u.com/2012/09/vincent-van-gogh/degradation-van-gogh-x-rays-unravel-painting-mysterious http://planetsave.com/2012/09/14/x-rays-uncover-the-mysterious-degradation-of-van-gogh-painting/ http://www.realclearscience.com/2012/09/05/mysterious_crust_on_van_gogh_paintings_248851.html http://www.ibtimes.com/articles/384594/20120914/van-gogh-color-change-chemistry.htm http://www.msnbc.msn.com/id/49033885/ns/technology_and_science-science http://www.redorbit.com/news/science/1112694555/van-gogh-painting-flowers-in-a-blue-vase-091512/ http://insciences.org/articles.php?tag=Cadmium%20yellow http://www.labspaces.net/123516/X_rays_unravel_mysterious_degradation_of_a_Van_Gogh_painting http://13lei.net/2012/09/15/van-goghs-flowers-in-a-blue-vase-damage-seen-in-x-rays-bbc-news/ http://www.artandcointv.com/blog/2012/09/cause-of-puzzling-color-change-in-van-gogh-painting-found/ http://www.azooptics.com/news.aspx?newsID=16105 http://www.nsearch.com/blogs/350/7945/x-rays-unravel-mysterious-degrad http://technology.newsplurk.com/2012/09/van-gogh-flowers-in-blue-vase-damage.html http://njuice.com/xrays-unravel-mysterious-degradation-of-vincent-van-gogh-painting http://www.coolestblogger.com/2012/van-goghs-flowers-in-a-blue-vase-damage-seen-in-x-rays-bbc-news/ http://www.stsnews.com/news-why-color-changed-in-van-gogh-painting/ http://scianswers.com/topic/chemical-cause-of-van-gogh-painting-color-change-discovered-redorbit/ http://frenchtribune.com/teneur/1213418-chemical-compound-damaging-flowers-van-goghs-blue-vase http://www.onenewspage.com/n/Technology/74rfhj9gk/Why-color-changed-in-Van-Gogh-painting.htm http://timesofindia.indiatimes.com/home/science/X-ray-reveals-why-flowers-in-Van-Goghs-painting-were-changing-colour/articleshow/16414157.cms http://www.democraticunderground.com/122810317 http://www.globalpost.com/dispatch/news/science/120915/van-gogh-painting-damaged-chemical-varnish http://forum.artinvestment.ru/showthread.php?t=170372&langid=5 http://www.grahamhancock.com/news/index.php http://songmoi.vn/van-hoa-nghe-thuat/sac-mau-bi-an-trong-tranh-van-gogh http://www.qwtnews.com/?p=1068811 http://ikono.org/2012/09/colours-in-van-goghs-painting-show-damage-in-x-rays/ http://updatednews.ca/2012/09/16/van-goghs-flowers-in-a-blue-vase-damage-seen-in-x-rays/ http://goodknews.com/entertainment/2012/09/15/x-rays-spot-van-gogh-work-dulling http://www.care2.com/news/member/543289044/3453586 http://en.paperblog.com/van-gogh-s-flowers-in-a-blue-vase-damage-seen-in-x-rays-307905/ http://theweirdbit.org/van-goghs-flowers-in-a-blue-vase-damage-seen-in-x-rays/ https://plus.google.com/118246412183062133215/posts/5vewGLKd7cY http://in.keegy.com/post/van-gogh-s-flowers-in-a-blue-vase-damage-seen-in-x-rays/ http://www.silobreaker.com/xrays-unravel-mysterious-degradation-of-a-van-gogh-painting-5_2265975645219586048 http://news.sudanvisiondaily.com/details.html?rsnpid=214215 http://www.chemistryviews.org/details/news/2575141/Mysterious_Degradation_of_Van_Gogh_Painting.html http://equityjungle.com/2012/09/18/why-van-goghs-flowers-are-changing-colors/ http://en.artron.net/news/news.php?newid=267001 http://www.materialstoday.com/view/28308/x-rays-unravel-mysterious-degradation/ http://www.wired-gov.net/wg/wg-news-1.nsf/0/DF94F76AE6E3885F80257A7E0034C0F7?OpenDocument In French http://www.metrofrance.com/lyon/grenoble-un-van-gogh-sous-l-il-du-synchrotron/mlip!vaGqWEEf7LuR2/
http://www.techno-science.net/?onglet=news&news=10822 http://www.newspress.fr/Communique_FR_258001_641.aspx Frankfurter Algemeine Zeitung, 10 October 2012
http://www.desy.de/infos__services/presse/pressemeldungen/@@news-view?id=3721&lang=ger
http://www.tagesschau.de/multimedia/video/sendungsbeitrag191816~_res-.html
http://idw-online.de/pages/de/news496299 http://www.extremnews.com/berichte/wissenschaft/cad01414c222405/511a1414c2224af/info http://science.orf.at/stories/1704858/ http://wissen.dradio.de/nachrichten.59.de.html?drn:news_id=136567 http://www.wissenschaft.de/wissenschaft/news/316172.html http://newsticker.sueddeutsche.de/list/id/1362093 http://www.cafe-europe.info/alle_texte/van-gogh-soll-wieder-strahlen/210313 http://www.sueddeutsche.de/wissen/van-gogh-gemaelde-firnis-veraendert-die-farbe-1.1470008 http://scinexx.de/wissen-aktuell-15139-2012-09-17.html
http://www.tafter.it/2012/09/14/arte-i-girasoli-di-van-gogh-ritrovano-il-loro-giallo-originario/ http://www.articolotre.com/2012/09/il-celebre-giallo-di-van-gogh-smette-di-brillare/108814 http://247.libero.it/focus/23098237/1/i-fiori-di-van-gogh-ritrovano-il-giallo-originario/ http://satarlanda.eu/2012/09/14/i-fiori-di-van-gogh-ritrovano-il-giallo-originario/ http://www.gazzettadelsud.it/news/cultura/13006/Ritrovato-il-giallo--di-Van-Gogh.html
http://www.abc.es/20120917/ciencia/abci-oxalato-envejecimiento-gogh-201209171616.html http://www.bbc.co.uk/mundo/noticias/2012/09/120915_cultura_pintura_van_gogh_daniada_bd.shtml http://www.elmundo.es/elmundo/2012/09/17/cultura/1347883374.html http://www.prensa-latina.cu/index.php?option=com_content&task=view&id=545487&Itemid=1
http://songmoi.vn/van-hoa-nghe-thuat/sac-mau-bi-an-trong-tranh-van-gogh
In Japanese http://torinosaezuri.wordpress.com/2012/09/18/yellow-of-van-gogh-ゴッホの黄/ In Swedish http://sverigesradio.se/sida/artikel.aspx?programid=478&artikel=5273173 http://www.standaard.be/artikel/detail.aspx?artikelid=DMF20120914_00296895
http://www.nwtonline.nl/nl/nieuws/19405/grauwe-van-gogh-verklaard.html http://nieuws247.com/news/van-goghs-bloemen-niet-grijs-door-verf-maar-door-vernis-de-standaard http://www.wetenschapsforum.nl/index.php/topic/177678-waarom-van-goghs-gele-bloemen-grijs-worden/ http://www.dejongeakademie.nl/Pages/DJA/33/915.bGFuZz1OTA.html http://article.wn.com/view/WNATf6b4e0b20db2d7029a7f7c1f293f74b0/ http://www.nd.nl/artikelen/2012/september/14/oorzaak-verkleuring-van-gogh-bekend http://www.rsscockpit.com/article.do?action=show&id=2165393837 http://www.scientias.nl/wetenschap-ontdekt-hoe-van-gogh-gele-bloemen-oranjegrijs-werden/72119 |
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12 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
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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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