Shortly before the mansion opened, we collected in these…and replaced them with new ones for another year.
These are dosimeters and can be found in all of the show rooms. They measure the amount of light each room is exposed to over the year.
Much of the collection at Attingham is sensitive to light. Textiles, paintings, furniture and wallpaper can all be damaged by UV rays, causing them to deteriorate. These photochemical reactions are irreversible and cannot be rectified by conservation treatment, and so it is a high priority for us to reduce any potential damage.
We monitor light exposure using these dosimeters which consist of dyed blue wool strips. The degree of fading, over a period of time, can be converted into numerical lux hours exposure by measuring the change in colour between the exposed and unexposed area of wool. (Light levels that fall on objects are measured in units of lux, and light exposure is measured in units of lux hours).
All the show rooms in the house are highly light sensitive, meaning that they are only allowed 150, 000 lux hours per year, except the Entrance Hall which is moderately sensitive (600, 000 lux hours).
One of the ways UV damage can be lessened is by reducing the amount of time an object is exposed to light. This is the main reason why Trust houses use blinds and shutters during the winter season and even sometimes when the house is open to the public during the day.