SQUINTING at dimly lit tapestries, costumes and silks could be a thing of the past if Britain鈥檚 museums and stately homes take up the results of a recent study. Turning up the light for a few moments, it turns out, would show off historical treasures to better effect without doing them any harm. 鈥淚t鈥檚 a way to give the public a better view and keep the conservators happy,鈥� says David Howell, the conservation scientist at the government-funded Historic Royal Palaces Agency who worked on the study.
In recent years, visitors to museums and stately homes have become accustomed to viewing historic textiles in dim light because conservators fear that the dyes will fade in bright light. Needless to say, the treasures are seen at their best when lit with brighter light. 鈥淚f conservators got their way, tapestries and the like would be kept in permanent darkness,鈥� says Howell.
Howell carried out his six-month study at the request of Simon Thurley, curator of Historic Royal Palaces, which include Kensington Palace and the Tower of London. The curator at Kensington Palace wanted to know how best to display the Royal Court dress collection, which includes many spectacular garments from Victorian times onwards. 鈥淣ormally, the costumes are kept in glass cases but it was hoped to show them to the public in a more interesting way鈥� says Howell. 鈥淭he curator wanted to know the optimum safe levels of light.鈥�
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Amazingly, no one had measured the effect of light on textiles in a systematic way before. Howell, working with scientists at the National Physical Laboratory in Teddington, illuminated large swatches of dyed woollen material and smaller pieces of undyed silk with different intensities of artificial light for varying lengths of time. The light was provided by tungsten lamps and the colour changes monitored with a spectrophotometer. Light, particularly ultraviolet, destroys the pigments in natural dyestuffs and damages the materials. Silk is one of the most vulnerable of all fabrics.
Howell discovered that there is no threshold 鈥渓ight dose鈥� below which textiles are safe and above which they suffer damage. 鈥淪uch damage is cumulative,鈥� he says. 鈥淚n such circumstances, the only real option is to try and minimise it.鈥�
The way to do this was suggested by Howell鈥檚 finding that in terms of the amount of damage done, the light intensity and exposure time are related in a reciprocal manner. In other words, the damage caused by a given light intensity in two hours is the same as that caused by double the light intensity in one hour. 鈥淭his suggests that the fading rate could be minimised while giving people a better look for less time,鈥� says Howell. Kensington Palace is considering running short guided tours of the Royal Court dress collection once every few hours instead of having a continuous trickle of visitors through the room. Howell recommends keeping the rooms dim until the tour walks in, when the light brightens, fading when they leave.
As part of the study, Howell also investigated the effect on textiles of humidity and flashbulbs. 鈥淎s far as flashbulbs are concerned, we came to the same conclusion as the National Gallery, which recently studied the effect on paintings,鈥� says Howell (This Week, 25 March). 鈥淵ou needed a bulb going off every minute of the day to cause any real damage.鈥�