Perilous Pigments: Analysing for Arsenic in Historic Wallpapers

This research by Dr Naomi Luxford (English Heritage), Dr Sarah Paynter (Historic England) and wallpaper specialist Dr Phillippa Mapes uses non-destructive analysis, by portable X-ray fluorescence, to identify arsenical pigments on historic wallpapers.

A portable X-ray fluorescence device being used on historic wallpaper.
A portable X-ray fluorescence device being used on historic wallpaper. © English Heritage.

Historic Wallpapers

Remnants of historic wallpapers sometimes survive in older properties and many others have been preserved as part of the Architectural Study Collection at Wrest Park (English Heritage).

Earlier wallpapers were hand painted or block-printed on small sheets, largely in black and white, but overtime they diversify into mass-produced, vividly coloured designs on continuous-length, machine-made paper. Developments in the 19th century meant that wallpaper became cheaper and more widely used; unfortunately the bright green pigment that was very popular at this time was arsenic-based, and was eventually discontinued on health grounds in the 1870s.

A fragment of historic wallpaper surviving behind wooden panelling.
Surviving historic wallpaper beneath a window, behind wooden panelling. © English Heritage.

Challenges

The research successfully identified arsenical pigments mainly in green colours on 19th-century papers, overcoming a number of analytical challenges in the process.

A detail showing layers of peeling historic wallpaper.
A detail of overlapping layers of different historic wallpapers. © English Heritage.

The results can be difficult to interpret because the XRF detects whatever is over or under the targeted wallpaper as well, whether plaster, paint, varnish, or multiple layers of older wallpaper.

A diagram showing tests for copper-arsenic pigments in historic wallpaper.
The results show that common copper-arsenic pigments were used for bright green (green circles on graph), copper pigments were used for blues and greens (blue diamonds on graph), and mixtures or overlapping layers were used to vary the shade of green (green stars on graph). © Historic England

The XRF uses X-rays to identify chemical elements. Lead emits similar energy X-rays to arsenic however, and unfortunately lead is common in historic paints and some wallpaper pigments too; this sometimes caused false positives for arsenic.

Rare survivals

Historic wallpaper tells many stories; the function of a room, the lives of the occupants, and the fashions and technology of the time. Research enables these rescued fragments to be safely cared for, so that they can continue to inform and inspire in the future.

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Sarah Paynter

Materials Scientist

Fort Cumberland,
Fort Cumberland Road,
Portsmouth,
P04 9LD

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