Running a historic house involves lots of different kinds of work, which we divide up into daily, weekly and annual jobs. One of the weekly jobs is to monitor the light, humidity and temperature. If the levels are wrong, than the collection deteriorates and becomes permanently damaged.
Light is one of the main causes of damage in any house, not just historic ones. It can be quite easy to see some of the damage through fading of colors but this is really only an outwardly sign of deeper damage. A high amount of light activates the chemicals, that make up the color, to react and change. One of the best examples that we have here of this is the velvet upholstery on the sofa and matching chairs in the Drawing Room – they used to be a bright rose-pink but are now green.
Light also affects the threads in fabric, causing them to break down and snap leading to tears and rips. Ever handled something that has fallen apart in your hands when you pick it up? This is what can happen to fabrics like curtains, carpets and tapestries.
Humidity levels are different for every type of object. For example, the correct humidity level for metals is too dry for wood, which would cause the wood to dry out and split. If the humidity is too low, organic materials like leather and wood shrink, crack and even in extreme cases, break. If the humidity levels are too high, than organic materials swell and stick, like drawers in a desk. High humidity causes dampness which in turn encourages mould and fungi. It also attracts insect pests and cause metals to rust.
Temperatures has two effects on collections. It is directly linked to humidity levels, so if it is hot, then humidity levels will be low and vice versa. Low temperature, especially sub-zero ones, will cause objects to become brittle and crack, whilst high temperatures can soften and melt some materials.
It can be difficult to find the right balance between these factors, which is why we monitor them at least once a week. In order to attempt to prevent damage, we have set budgets. In every room, there are certain objects that have been deemed as at a higher risk than others, which is determined by several factors, their materials or their historical significance to the house. These are the objects that we measure off using an environmental monitor.
This measure light or lux levels, relative humidity (RH) and temperature. We record it manually and take action a level is too high or low. Light is the easiest to fix as we can adjust the blinds, which is why it can sometimes be a little bit dark at times. Humidity and temperature is a bit harder to fix as it often involves adjusting heating levels and putting out humidifiers/de-humidifiers.