Senior collections conservator Rachel Turnbull wheeled a pair of ultraviolet lights into position, handed me some protective glasses and flicked a switch. Bathed in blue light, the layer of old varnish that covers Diana Cecil, 1st Countess of Elgin – a painting by Cornelius Johnson (1593–1661) from the esteemed collection at Kenwood in London – jumped out at us, bright against the area of the painting that’s already been carefully cleaned. It’s like a magic trick.

Looking more closely, the UV light revealed other secrets: damage to the work, areas of historic restoration, and details that had become obscured over the nearly four centuries since Johnson painted this portrait. The best bit? Johnson’s initials and the date he completed this work, 1634, tucked away in a fold of dark drapery, practically impossible to see in normal light.

‘People did know that it was signed but it’s been lost in the last few years,’ said Turnbull, excitedly. She had invited me to take a look around the conservation studio as 2022 marked the centenary of the setting up of the first ever dedicated, government-employed team of artist-restorers tasked with repairing, cleaning and conserving the paintings in the various national collections. There had been museum restoration departments before this point, but they relied on private external workshops. It was only in 1922 that the government’s director of works in charge of royal palaces, the Houses of Parliament, public and historic buildings and ancient monuments began the process of bringing these roles in-house.

That’s not to say that the current team is stuck in the past. By looking at a painting or a paint sample under UV light, using state-of-the-art infrared imaging, microscopy or X-rays, conservators can learn myriad details about the condition of a work of art. Such tools are also revealing of how an artist worked, their methods and materials, allowing conservators to work together with curators and art historians to gain a better understanding of a painting in its historical context.

Such investigation wasn’t necessarily of much interest to the artist-restorers of yesteryear. ‘They were focused on a painting’s surface and aesthetics,’ said Tate-Harte. ‘When they were doing their restoration they would quite happily repaint things. We just don’t do that.’

By the 1950s, the Artists’ Section had in its remit some 3,000 paintings – works cared for today by English Heritage as well as Historic Royal Palaces, the Houses of Parliament, the National Trust, the Government Art Collection, Westminster Abbey, the V&A and the Royal Collection. The artists worked fast, either in situ in the case of paintings such as the Thornhill Ceiling at the Old Royal Naval College in Greenwich, or in makeshift studios such as the one set up in the Orangery at Kensington Palace to work on the Rubens ceiling murals from Banqueting House.

Working conditions were far from ideal, as is clear from photographs taken at the time of the artists standing atop towering scaffolds with no safety equipment, using carcinogenic solvents. The Kensington Palace studio wasn’t much better, with one artist writing in March 1947 that there was no heating because they had run out of fuel and that the studio was ‘extremely damp and dangerous to health’. Jack complained in a letter to a manager the following year that ‘it is impossible to imagine any Civil Servant at Lambeth Bridge House writing an important report with rain pouring through the roof’.

In the frame

‘Part of our treatment is quite preventive as well,’ Tate-Harte added, pointing towards a carved gilt frame whose back she and Turnbull have built up in order to be able to create a safe environment within which its painting can sit. Where once works were nailed back into frames whose coarse edges would scratch the vulnerable surface of the paintings, now they are carefully cushioned on all sides and protected from accidental damage with a hard back board.

In the case of paintings located in properties whose atmospheric conditions are difficult to control – draughty castles such as Bolsover in Derbyshire, for example – a frame can be designed to create a microclimate for a painting, complete with its own computerised environmental monitoring.

Such technical interventions, as well as an auditing system that prioritises paintings for treatment based on nearly four decades of record keeping, mean that although the team treat far fewer works per year than the ‘men in tweed suits’ once did, the paintings in English Heritage’s care are in better hands than ever before.

‘You are objective in what you choose to treat and why,’ explained Turnbull. ‘We pick the things in the worst condition first.’ In the course of treating the paintings in the collection, the conservators are engaged in a dialogue through history – not just with the original artists but with the restorers who’ve worked on those paintings in the past. Turnbull and Tate-Harte are aware of their own roles in the lives of these works – taking notes and photos of their interventions to help future conservators is a key part of the process. As Tate-Harte put it, ‘Our legacy is to ensure the ongoing preservation of the collection for the next 100 years.’