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Invisible graphene veil protects paintings from fading

22/07/2021 A transparent layer of graphene, just a few atoms thick, can prevent pigments in paintings from fading by protecting them from ultraviolet light, moisture and air pollutants.
Colour fading is a major problem for painted artworks. Vincent van Gogh’s famous Sunflowers paintings, for example, contain photosensitive lead pigments. Originally bright yellow, they have turned greenish-brown over time.

A graphene veil can prevent up to 70% of colour fading, the researchers behind the work suggest. While the exact amount of protection depends on the colours and the pigment substrate, ‘this corresponds approximately to 200 years of exposure under the conditions encountered in museums or other exhibition environments’, says study leader Costas Galiotis of the Foundation for Research and Technology Hellas in Greece.

‘Graphene absorbs a considerable amount of ultraviolet light, depending on the number of layers, and is a very good barrier against oxygen and moisture,’ Galiotis explains. ‘It prevents colour fading by simultaneously reducing the incident harmful radiation and by delaying the diffusion of oxidising agents.’

Galiotis and his colleagues devised a machine to apply the veil to a painting, using atomically-thin graphene lattices grown by vapour deposition on a copper substrate that are transferred onto adhesive film. Two rollers gently press the painting and the film together, and then remove the film, leaving only the graphene layer.

The researchers exposed coloured disks protected by layers of graphene to high levels of light, warmth and humidity – an artificial ageing process. They also examined the effects on a painting – Indian inks on glossy paper – covering one half with their graphene veil while leaving the other unprotected. After the painting had been left in the ageing chamber for more than 1000 hours the colours on the unprotected half had noticeably faded – but the colours protected by the graphene veil held fast.

Schematic illustration of the roll-to-roll process used to transfer graphene onto mock-ups and real  artworks
Source: © M Kotsidi et al/Springer Nature Limited 2021

Graphene is grown as an ultra-thin layer on copper, transferred onto an adhesive layer and then pressed onto the painting between two rollers
Narayan Khandekar, director of the Straus Center for Consolation and Technical Studies at the Harvard Art Museums, US, explains that museums limit colour fading by keeping paintings in dark storage and displaying them for only short periods under low-energy lights. But most paintings in private residences receive no such treatment, he says. The idea of a protective graphene veil is ‘really compelling – it’s something that seems to mitigate a lot of light damage and its easily removed. So I think it has a lot of potential.’ He notes, however, that paintings are often protected by a layer of specialised resin or varnish, and researchers now need to examine how these interact with the graphene veil.

Art conservation scientist Stephen Hackney, formerly of the Tate Gallery in London, UK, explains that conservators need ‘full knowledge’ of the materials used on a painted artwork and how they behave. ‘This is a tall order, but a valid requirement that makes innovation difficult.’

Although some of the properties of the protective veil seem promising, ‘in my experience it takes a relatively long time for new materials to be accepted and adopted, and it is often the practical procedures, rather than the materials themselves, that need most thought’, Hackney says.

Source: https://bit.ly/3xV3hW1, via Chemistry World
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