Controlled Atmosphere Treatment (CAT) protects exhibits and cultural heritage

01 February, 2005

Gentle way to conserve works of art

The conservation of works of art over decades or centuries ranks among the key challenges confronting museums, art galleries and libraries. Light, damp or other atmospheric factors, not to mention air-borne spores and the natural ageing process of the original materials, all contribute to the deterioration of paintings, books and sculptures, making conservation essential if exhibits are to survive for future generations. Another major cause of damage is pests – such as the Varied Carpet Beetle or the Common Clothes Moth. Organic materials are particularly at risk, especially when exposed to changing conditions such as those during peripatetic exhibitions.

Special technology for pest control in museums

A world leader in pest control, Rentokil is renowned for its innovative methods: the Practice Centre at the company’s Dortmund branch in Germany specialises in museums and works of art. The centre has helped numerous German museums in their battle against pest damage to organic materials. The work is done on location in the museum, using a mobile system, which is installed for as long as necessary – eliminating the possibility of damage in transit, while also minimising the risk of theft.

Affected exhibits undergo what is called Controlled Atmosphere Treatment (CAT). It involves exposure to nitrogen for several weeks in a gas-filled bubble. Packed in a special gas-tight film, exhibits are surrounded by an atmosphere of 99% nitrogen - sufficient to suffocate all organic life, even pupating insects with their much reduced metabolism.

As the film is cut and heat-sealed to the dimensions specified, there is virtually no limit to the size of objects treated. Sizeable objects treated to date include a covered wagon and historical press (done in the same bubble) and various Egyptian sculptures. In the Citizen's Theatre, Glasgow, Scotland, the CAT system eliminated the Common Clothes Moth in some 10,000 costumes. It has also helped conserve art treasures in leading German museums, e.g. the Museum for Applied Art in Cologne. Another prominent name on Rentokil Initial's reference list is the Schloss Moyland art collection near Kleve.

In the words of Jens Heuter, Marketing Manager at Rentokil Initial, "CAT systems have proved themselves internationally in numerous applications - in archives, museums, churches, and also theatres. Nitrogen does not harm foodstuffs, and indeed is widely used to protect spices. We have even treated the corks in a valuable batch of Champagne, ensuring the contents retained their sophisticated flavour."

Controlled atmosphere in a bubble

The high concentration of nitrogen is achieved by "rinsing" the bubble several times with the gas to wash out residual oxygen in the exhibit. The film, which is individually tailored to each assignment, facilitates the creation of a controlled atmosphere. Before entering the bubble, the nitrogen goes through a humidifier, which ensures that gas passing into the film has the same humidity as the ambient air. Inside the bubble, a thermohydrograph registers the gas temperature and humidity throughout.

When, several weeks later, the Rentokil Initial specialists open the bubble, the nitrogen is immediately extracted and released outside the building, eliminating risk to people in the room. For ecological reasons, Rentokil Initial normally uses atmospheric gases only. Nitrogen is less hazardous than carbon dioxide, which is widely used in similar applications. With both gases, however, treated objects can be used as soon as the treatment ends. To mark the successful treatment, Rentokil Initial provides a certificate, which the museum or library management can use for internal documentation.

Notes to editors:

Rentokil Initial is one of the largest business services companies in the world, its 90,000 employees operating in 40 different countries on every continent. The company has been active in Germany since 1961 and has four main operations: washroom services, pest control, hygiene services and interior plants landscaping. A countrywide network of 31 offices ensures prompt service and provides strategies and solutions for companies of any size and in any line of business. Each one of Rentokil Initial's business units is a technology and innovation leader in its field. The company is also involved in industry committees, fulfils all legally required standards and holds all necessary licenses.