Suffocation is the latest weapon being used in the war against insect pests. The simple treatment involves keeping an artwork in an oxygen-free situation for a fortnight. This avoids the need to use toxic gas or chemicals, reducing the dangers to human health or the environment. The suffocation method also means that chemicals which might possibly affect the appearance of a painted surface do not have to be used.
Researchers at the Getty Conservation Institute and the J. Paul Getty Museum in Los Angeles have conducted “low oxygen fumigation” tests on the ten most common insects which damage museum objects. Their “hit list” comprised webbing clothes moths, furniture carpet beetles, firebrats, cabinet beetles, larder beetles, cigarette beetles, confused flour beetles, cockroaches, powder post beetles and western drywood termites.
The trials showed that when deprived of oxygen, adult firebrats died after just three hours. The most resistant pest, cigarette beetle eggs, took eight days to die.
Research has been underway on the best way to treat works of art, which have to be encased in a plastic pouch. One method of reducing the oxygen level is continuously to purge the pouch with an inert gas, such as nitrogen.
The alternative is to use an oxygen “scavenger”, a substance comprising iron oxide and potassium chloride which produces a chemical reaction that absorbs the oxygen. After the oxygen concentration has been reduced from the normal twenty-one percent found in air to 0.1 per cent, the artwork is kept in the pouch for a recommended fourteen days.
Low oxygen fumigation has been used by the Getty Museum to treat furniture, pictures and wooden sculptures. The most recent trials, undertaken by Gordon Hanlon, have centred on the treatment of panel paintings, which are vulnerable to wood-boring insects such as woodworm, death watch beetles, powder post beetles, house longhorn beetles and termites. These lay their eggs on unpainted areas. At the larval stage, the insects bore into the wood, with the adults ultimately emerging through flight holes.
In Britain, the National Trust has started to use low oxygen fumigation. Artworks in its hundreds of country houses are inevitably more vulnerable to insect pests than those in museums. Curtains at Mottisfont Abbey, in Hampshire, have been successfully treated for moths. Later this year the National Trust plans to introduce low oxygen fumigation for wooden panel paintings, frames and stretchers.
Originally appeared in The Art Newspaper as 'Kill that Bug'