This week the House team were presented with a brand new piece of kit, a new environmental monitor. Needless to say we were very excited and set about using it straight away! Environmental monitoring is an extremely important part of the work we do here at Polesden Lacey as it ensures that we can prevent any further damage or deterioration to the collections.
Until now we have been using two different pieces of equipment for measuring light levels, temperature and relative humidity. Our new environmental monitor has all these features in one handy device. This wonderful environmental monitor measures ultra violet light (measured in lumens), visible light (measured in lux), temperature and relative humidity (percentage), all of which are very important for our daily monitoring.
Light is one of the most damaging agents of decay that can affect objects. It can cause the fading of dyes, pigments, organic materials and can result in the weakening of textiles and works of art on paper. There are recommended maximum levels of exposure for all our objects and as a result we have an extensive light plan. When we set the blinds in each room we check the light level by holding the environmental monitor against the most vulnerable object. For textiles, upholstery and carpets the maximum level should be 90 lux (to give you a general idea; the average household light bulb gives out around 50 lux and the brighter strip lights you might see in offices give off around 80 lux). Furniture and paintings can withhold a slightly higher levels of light exposure but it is still important to keep an eye on the amount of light falling on these objects, particularly if they have suffered previous damage or deterioration as a result of over exposure.
When you visit, you may spot us in the house moving blinds up or down whilst holding our environmental monitor up against an item of the collection that is highly sensitive to light. We have to keep a very close eye on the light levels throughout the day; checking them at least three times throughout the day and sometimes more if the weather is particularly changeable.
Relative Humidity (RH) is another agent of decay that can affect our collection and drastic fluctuations can easily affect objects made of organic materials. Ideally we are looking for the humidity levels in the house to be between 40% and 65% RH. When humidity is low (below 40%) these objects can shrink and cracks or breaks will appear. When humidity is high (above 65%) organic materials will swell. In this case we often find that drawers stick and doors will not open easily. If we see that the RH is particularly high we have to take special measures, such as using additional heaters to dry the air out and attempt to reduce the impact on the objects in the collection.
The weather over the past few weeks have been particularly damp but also quite warm. This has meant that we have had to be extra vigilant by keeping an even closer eye on temperature and relative humidity levels in the house. We have Hanwell monitors in most rooms which send out readings once an hour, and the information collected from these can be viewed and monitored on our computer. We also take spot check readings in all the rooms once or twice a week. From this data we create reports which are used in our important curatorial and conservation meetings.
Needless to say our new monitor is a very welcome addition to the team and we are already putting it to good use, hopefully with a positive outcome!