Camera brings ‘unprecedented clarity’ to restoration of historic artworks

Scientists have developed technology that will revolutionise the restoration of historic works of art by allowing conservators to identify and remove ageing varnish with total accuracy.

A team at King’s College London’s department of physics has harnessed the power of fluorescence to bring “unprecedented clarity” to the conservation process, said Prof Klaus Suhling.

A revolutionary camera will allow experts to distinguish between varnish and other components in an artwork, such as paints and binders.

“The conservation of paintings is vital to protect our cultural heritage for generations to come,” said Suhling.

“Most paintings created before the late 19th century have been varnished many times, making them appear dull or yellowed as the varnish degrades. To make the image visible again, it may be necessary to remove that varnish – but it can be a big challenge to differentiate this from the underlying paint and other components within the painting.”

The King’s College team developed a 25,000-pixel photon sensitive camera that uses a technique called macroscopic fluorescence lifetime imaging (FLIM) to harness the natural fluorescence in centuries-old varnish.

Each pixel has a stopwatch that measures when the light from a surface enters it. “By comparing the fluorescence of the varnish to these other components, we can chart where varnish sits with a level of accuracy never previously achieved,” said Suhling.

Usually conservators shine UV lamps on the surface of a painting to ascertain residue by eye. The method relies on the expertise of the conservator and involves a degree of guesswork.

The King’s College team, led by Suhling and Dr Jakub Nedbal, worked with the Courtauld and the University of Edinburgh on the project.

Prof Aviva Burnstock, of the Courtauld, said the new technique “provided more detailed information about the paint and varnish during removal tests than any other previous method, paving the way for whole painting imaging during varnish removal”.

“If achieved, that would be a great advance for painting conservators.”

Suhling said the camera would not be expensive to produce in the future as it was derived from consumer technology such as smartphone cameras. “It’s very bespoke [now] but in the future I think it will be relatively low cost.”

Fluorescence is typically used in medicine to study, track and identify cancerous cells. It is also used in polymer banknotes as a security measure.

Suhling said he was a regular visitor to art galleries. “I was keen to use my expertise to advance conservation work,” he said.

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