Light

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.

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 time.

Back to The Suspects