Iconic paintings' true colours revealed

By Sarah Knapton, Science Correspondent

The vibrant colours of Renoir, Van Gough and Picasso have been shown for the first time in more than a century after scans of paintings revealed how much paint had degraded. 

Scientists have been working with conservators to analyse the molecular make up of paint used in some of the great masterpieces and determine how much is has faded over time. 

They discovered that Renoir’s Madame Leon Clappison was originally posing in front of vibrant red background. 

Previously scholars had believed that the artist had painted an abstract background with swirls of colour picking blues from her dress, and yellows from her gloves. 

Richard Van Duyne, professor of chemistry at Northwestern University in Illinois, used a Surface Enhanced Raman Scattering (SERS) scanning technique to identify the chemical components in Renoir’s paints. 

He unveiled a new digital visualization of how the original colours would have looked at the American Association for the Advancement of Science’s annual meeting in Chicago yesterday. 

Prof Van Duyne said: “Every molecule vibrates differently and so we can use the spectroscopic method to determine the molecular make-up of paint. 

“Fading has been going on, so looking under the frame can tell us what they should be now. 

“You can see that the background is much more red.” 

Prof Joris Dik of Delft University of Technology in The Netherlands has been carrying out a similar project on Van Gough’s Flowers in a Blue Vase. 

A scan of the painting revealed a thick crust over the areas which had been painted with the pigment Cadmium Yellow. 

When he examined how that compound had faded over the past 100 years Prof Dik discovered that the muddy orange flowers which have been studied by scholars for decades were in fact bright yellow. 

“When you look at it with the brighter yellow the painting has much greater depth,” said Dik. 

He has also used the study of paint molecules to prove that some of Picasso masterpieces were created from a common blue house paint which would have been common in France at the period.