Our museum contains objects made from many different materials, including fur, textile, leather, wood, plastic and metal. Many of these materials, especially the furs and textiles, are susceptible to insect attack from moths and some varieties of beetles, such as the vodka beetle, and our best defence against them is FREEZING COLD. Often the insects might not themselves be visible, more often we see the surface evidence of insect activity only, such as bald patches where they have been grazing, frass (droppings), cast skins, or larval cases.
It is almost impossible to eradicate such pests from an old building like ours so we maintain a check of the situation by using small sticky traps placed at strategic points throughout the building which are regularly inspected:
However, monitoring and trapping is not failsafe – outbreaks of infestation can happen. Cracks, vents, and drains all give insects access to every part of the building and this includes the basement where the museum stores are located. Once in, if they find the food they are looking for they can quickly spread and, unchecked, can cause irreparable damage in a matter of only weeks:
Low temperature control is an established technique used to kill insects within museum collections. Cooling a room below +15 ºC can slow or stop the growth, feeding and breeding of museum insect pests, but subjecting them to temperatures of lower than -20ºC will eradicate the insects, their larvae and eggs for good.
At The Polar Museum, our practice is to routinely freeze all organic material coming in from outside the building even if no pest is evident, unless the items are felt to be at high risk of damage from freezing – we do not want to risk the infestation of an object spreading to the rest of our collections. This is the procedure for not only new acquisitions but also for our own objects when they are returned after having been on loan to another museum for temporary exhibition, as we cannot be one hundred percent certain they have not been exposed to pests whilst away. The objects are wrapped in clear polyethylene and sealed with tape before freezing. We wrap them not only to immediately contain the potential infestation, but also to prevent moisture changes in the object during freezing which could result in possible dimensional changes which can cause cracks, for example. We are very fortunate in that we have on the premises a walk-in room sized cold room, which can be set to a very chilly -34 ºC. No pest yet discovered can survive a week at this temperature!
We have many materials within our collection that could be damaged by freezing temperatures, such as rubber (in goggles and footwear), liquid (medical supplies, including thermometers and pharmaceuticals, and high precision scientific instruments such as compasses) oil paint and varnished objects. These objects cannot be frozen, and so instead are wrapped in polyethylene and returned to the stores and monitored for any tell-tale sign of pest activity.
On occasion we have been able to help other museums in Cambridge who do not have the luxury of a walk-in cold room as we do. Recently we were approached by Kettles Yard, an art gallery and house, who are currently preparing for a major building project to improve and build upon their education and gallery spaces. Whilst in the process of packing and moving the collections for safekeeping during the building work, they discovered a number of live moths emerging from some of the textiles, specifically from a collection of rugs, and contacted us immediately for help! Luckily the cold room was not being used so we could offer to freeze all of the affected objects – a total of 25 large rugs- in one batch. They arrived a few days later, with the rugs all tightly wrapped and labelled, and we set about navigating them through the building and down three flights of stairs to stack ready for the cold room.
Walking into a freezer set at -34 ºC is not without risk, however – hypothermia can lead to death, so whilst the risk of something going wrong is low, the severity of the situation if it did, would be major. Accordingly, lone working is never to be undertaken, and we have procedures in place for staff use of the cold room to ensure risk is mitigated. External users are given induction training in the safe use of the cold room and are asked to read and sign a risk assessment. Warm clothes, sensible shoes and gloves are to be worn. As an extra safety precaution, we must have a ‘buddy’ elsewhere in the building who knows what time we enter the cold room, and what time we expect to be out. If we have not reported back by the pre-arranged time they must come and check we haven’t managed to slip, knock our heads together and pass out in the freezing temperatures. Hypothermia is not something we take lightly, here at The Polar Museum.
The freezing of the rugs from Kettles Yard went well. After a week and a half (for good measure), Sophie and I braved the cold again and removed the frozen rugs from the cold room, laying them in the basement, still wrapped, to slowly come back up to temperature. Another success in the battle against infestation! RIP, museum pests.