Legendary crime writer Dame Agatha Christie may have sold more novels than any other writer, but did you know she was also a pioneer in object conservation? Working in Iraq alongside her archaeologist husband Sir Max Mallowan, Christie used improvised tools and cold cream originally intended for her own face to clean thousands of excavated fragments known as the Nimrud Ivories.
Lid of a 19th century ceramic cold cream container excavated from Little Lon, Melbourne and part of MV's Little Lon Collection.
Source: Museum Victoria
Cold cream is a mixture (or emulsion) of water in oil used to clean and soften the skin. Its name originates from the cold feeling left when the water component draws evaporates from the skin. But why was it useful for ivory? And is it still used for that purpose today? Senior Conservator Helen Privett helps to preserve objects in Museum Victoria's collection and she was happy to talk about contemporary tricks of the trade.
'We wouldn't use cold cream, but we use moisturising agents like it, such as polyethylene glycol which you find in modern cosmetics," says Helen. "The reason why you might use something like that is that you don't want to get ivory too wet, because it absorbs water and then expands to different degrees in different directions... a kind of multidimensional swelling which can cause cracking and distortion."
"We've got data loggers in the Mesopotamia showcases to monitor the environmental conditions. The showcases containing ivories are all set to about 55 per cent relative humidity to make sure they don't get too wet or too dry."
Approaches to artefact conservation have changed profoundly since Agatha Christie's time, and not just in terms of technological advances. There have been philosophical changes too: now the focus is on the long-term stability of the objects, which sometimes means a hands-off approach. Importantly, conservators don't necessarily clean artefacts any more.
"One issue in archaeological conservation is that you're removing objects from where they've sat for thousands of years," explains Helen. "Sometimes they're actually quite stable in that environment, and it's better to leave something buried than to bring it out of the ground." In the case of shipwrecks and certain archaeological sites, reburial of artefacts is becoming an accepted technique for preservation.
When cleaning or other treatment is required, conservators turn to a variety of materials. Many are chemicals that you might have in your own home, such as methyl cellulose (found in toothpastes, artificial tears and moisturisers) which is a useful adhesive and a poultice base, and citric acid (found in soft drinks) which is a gentle way to remove corrosion.
Senior Conservator Helen Privett holding a giant bucket of citric acid in the MV Conservation Lab.
Source: Museum Victoria
Helen describes the global community of conservators as open and willing to exchange information about new conservation techniques and materials through articles and online forums. "There are some adhesives, for example, that are made specifically for the conservation industry but because it's such a small field we tend to use materials from other industries. We do a lot of testing ourselves, particularly for new environmentally sustainable display materials."
Becoming a conservator usually requires a sound background in art history combined with broad training in materials science and applied chemistry. Then there's the tricky decision about which sub-specialty to enter; conservators can specialise in particular fields such as paintings, paper, or objects. For Helen, it was a single moment that led her to object conservation – seeing the Portland Vase in the British Museum. "It's very deep, intense translucent blue glass with a carved white relief. They've never been able to replicate how it was made. This amazing object was smashed into hundreds of pieces and has been put back together numerous times, so it's got this extraordinary history of manufacture, collection and conservation. It's my inspiration."
The Portland Vase, perhaps from Rome, Italy, about AD 5-25.
Source: © Trustees of the British Museum
Not every object is as monumental as the Portland Vase, and Museum Victoria's collection encompasses many types of materials, including a few that are notoriously difficult to conserve. When asked about her least favourite material, Helen doesn't mince words. "I love plastics, but I hate PVC. It's got what we call 'inherent vice' – it will deteriorate under any circumstances and was never meant to last. Because of the chlorides in the polymer, when it starts to deteriorate it forms hydrochloric acid and basically eats itself to death. PVC objects start to get sticky or tacky, or stuck in a certain shape and they're just a nightmare."
The Art of the Conservator (1992). Andrew Eddy (editor), British Museum Press, London.
Ladies of the Field: Early Women Archaeologists and Their Search for Adventure (2010). Amanda Adams, Greystone Books, Canada.
Murder in Mesopotamia: Agatha Christie and Archaeology forum at Melbourne Museum on Sunday 9 September
'British Museum buys 3,000-year-old ivory carvings Agatha Christie cleaned with her face cream' (Daily Mail, 8 March 2011)
Australian Historic Shipwreck Preservation Project