Van Gogh's paintings turning brown - scientists discover why

Add to My Stories Their vibrant colours have fascinated art lovers for more than 120 years.But time and sunlight have taken their toil on the world's most famous sunflowers.Over the generations, to the frustration of gallery owners, the striking yellows that feature in so many of Vincent van Gogh's paintings have faded to a dull brown.But now help is on hand.

The paint van Gogh used in his work The Yellow House has clearly faded against the blue sky - and researchers have now discovered why

L'Allee des Alyscamps and Fourteen Sunflowers show off the artist's use of the chrome yellow pigments that first appeared during the early 1800s

The scientists examined samples of yellow paint from the artist's Bank Of The Seine using X-rays. 200um equates to 1/5 of a millimetreUsing power X-rays, scientists have discovered why the yellow pigment used by Van Gogh and fellow 19th century artists have degraded so badly over the past century.

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The findings should prevent the paintings losing any more of their colour - and could even help art restorers devise new ways to return van Gogh's paintings to their former glory.

Van Gogh's use of vibrant colours to convey mood and emotion was a milestone in the history of art and influenced generations of paintersElla Hendriks of the Van Gog! h Museum Amsterdam said: 'This type of cutting edge research is crucial to advance our understanding of how paintings age and should be conserved for future generations.'Van Goghs use of vibrant colours to convey mood and emotion was a milestone in the history of art and influenced generations of painters.His approach to colour was largely possible because of the new pigments that emerged during the industrial revolution.The new study looked at one of the 'new' paints - chrome yellow - which first appeared in the early 1800s. The warm orange-yellow paint was made of toxic lead chromate and like many of the pigments of the period was chemically unstable.Even in the 19th century, painters knew that it turned to brown or faded over time. However, art restorers have long puzzled over why not all paintings using chrome yellow fade - and why some darken faster than others.The team of international scientists collected samples from three historic, half-used tubes of paint.After the samples were artificially aged for 500 hours under an ultraviolet lamp, only one sample - from a paint tube belonging to the Flemish artist Rik Wouters, darkened to a chocolate brown.The scientists used the same methods to study samples from two van Gogh paintings - his 1888 View of Arles with Irises, and his 1887 Bank of the Seine from the Van Gogh Museum, Amsterdam.The sample was analysed using an array of analytical tools, including the synchrotron X-ray equipment at the European Synchrotron Radiation Facility (ESRF) in Grenoble, France.

The different contrast in the yellow colours used by the artist can be seen in Wheat Fields With Reaper, which was exhibited at the Royal Academy of Arts in Central London last yearUsing the synchrotron's microscopic beam of X-rays one hundred times thinner than the width of human hair, they found that a chemical reaction called oxidation reduction was altering the chromium atoms! in the paint.The reaction - which leads to chromium atoms gaining extra electrons - is triggered by sunlight and UV light penetrating the surface of the paint.The change was most common in the presence of sulphur and barium - ingredients added to lead white paint in the 19th century. The scientists believe van Gogh's technique of blending white and yellow paint may have caused the fading.

18th century painters knew that their paints turned brown over time, but restorers have long wondered why some deteriorated at different rates

Dr Koen Janssens from Antwerp University, who published the findings in the journal Analytical Chemistry, said: '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.'Dr Marine Cotte, an ESRF scientist also working at La Muse du Louvre, said: '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.'