This 17th century embroidery of Venus & Juno shows signs of light damage. The reverse, above right, which was protected by a frame,
shows how it once looked.
Light waves are part of the electromagnetic spectrum.
There are different types of waves, all of which can
damage objects over time:
- we see visible light waves as colour
- our eyes cannot see ultraviolet (UV) light waves but some animals, like bees, can. These are the most
damaging waves, both to our skin and to our objects
- we sense infrared light waves as heat
Light is energy and it harms objects by starting damaging chemical reactions. It fades colours and weakens
organic materials, like textiles and paper, so that they break or tear easily.
Light has shattered the silk in this 17th century embroidery
Unfortunately the damage done by light is almost unavoidable, permanent, and further exposure will cause more
harm. However, conservators can take steps to limit the damage by controlling the
intensity and amount of light to which
objects are exposed:
- limit the amount of time objects spend on show in galleries by swapping displays around
- use low lighting on displays. A maximum of 50 lux
is recommended for very sensitive materials like
watercolours, and 200 lux for less sensitive materials
- filter out any UV
- avoid exposing objects to daylight, and keep curtains/blinds/shutters etc shut
- keep sensitive items covered and lights off when there are no visitors present
Conservators can watch for the effects of light by placing Blue Wool Standard cards near to objects on display.
The Blue Wool Standards are graded from 1 to 8; 1 fades very easily, while 8 does not fade even at high light levels. Dyes are
classified by comparison to these standards, so if we know what dyes were used to colour textiles in our collections then we can
refer to the appropriate Blue Wool Standards to figure out what would be a safe level of illuminance for a given amount of display
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