July 23, 2015
Have you ever walked into a museum gallery and had to wait a second for your eyes to adjust to the darkened space?
Ever tried to read the fine print on a text panel or get a glimpse of the details on an artifact, only to give up after a few minutes cause you didn’t have enough light?
If none of this rings a bell, then congratulations! You’re most likely under 40 and can still see perfectly fine in low lighting. But for everyone else who can relate to this common phenomenon in museums, you must have wondered, “Why are they keeping all these beautiful artifacts in the dark?”
Believe it or not, museums aren’t out to punish you for aging past 40. The real reason behind all the dim lighting is that most museums are just trying to fight the negative effects of light exposure on their historical artifacts.
Light, in all its wonderful illuminating glory, is actually one of the most aggressive, harmful, and irreversible agents of deterioration when it comes to museum collections.
See, you can glue a broken pot back together. You can clean a stain off a costume. You can even dry out a waterlogged book. But there is nothing — and I mean nothing — you can do once light damage has occurred. Sure you can shove the object in a box and turn off the light, but the damage has already been done.
Light damage to historical artifacts is like that horrible tattoo you got when you were younger. It’s in an unflattering location, it’s permanent, and it’s only getting worse with time.
Country musician Wilf Carter’s suit from NMC’s Canadian Country Music Hall of Fame collection. Thanks to light damage, the jacket appears a significantly lighter shade than the pants. Credit: Gail Niinimaa
Out of the plethora of objects you might find in a museum, the types of items that are especially susceptible to light degradation are those that contain organic components. This includes paper, wood, fur, skin and feathers, organic oils and varnishes, plastics, and of course, textiles.
Textiles in particular are extremely sensitive to light damage, due to the multiple ways in which light’s energy can damage the material. Not only does light cause the organic fibres and dyes in textiles to bleach and fade over time, but the chemical reactions brought on by light can also prompt fibres to break down, fray, and eventually tear.
As seen in the image above, light damage is particularly noticeable when bright dyes in textiles are exposed. Before coming into NMC’s care, Wilf Carter’s suit sat on display under halogen lighting for years at a time. This continual exposure to intense light levels has resulted in the original bright pink colour, still visible in areas where light hasn’t yet touched, fading to a pale salmon hue.
The formula for light damage has two main ingredients:
- Level of illumination
- Duration of exposure
What this means, is that it is not just how bright the lights are, but also the total, or cumulative, exposure of an artifact to light over time, that makes a difference. It doesn’t matter if an artifact was directly under a fluorescent bulb for 20 days, or beside a flickering candle for 200 years, the amount of damage and exposure is the same.
Hold up. A flickering candle is just as bad as a fluorescent light bulb?
Yes! As long as it is exposed for a long enough amount of time. Surprisingly enough, an object will incur the same amount of damage from exposure to bright light for a brief period of time as from low light for a long period of time.
How do we know this? By measuring the light levels of different light sources.
Light intensity, or illuminance, is measured in lux. A couple candles, for example, would probably give you about 50 lux worth of luminance, while a fluorescent bulb may be closer to 500 lux. For comparison’s sake, light levels outside in full daylight can be anywhere from 10,000 – 100,000 lux, thereby making natural sunlight the most damaging light source by far.
From there, it’s just simple math: 5 or more candles burning for 200 years at 50 lux results in the same amount of exposure as a fluorescent bulb for 20 days at 500 lux.
This is why light levels in museums are kept so low. By limiting the amount of light an artifact is exposed to, we can therefore extend the life of that artifact many years past its “natural expiry date.”
Close up of light damage on country musician Lucille Starr’s dress from NMC’s Canadian Country Music Hall of Fame collection. Over time, light has infiltrated the cracks between the fringe details on Starr’s outfit, leaving streaks of faded dye underneath. Credit: Gail Niinimaa
Obviously, from a conservator’s perspective, the best type of light is no light at all. But this isn’t very realistic. Increasingly, we are also finding that the low light levels employed by most museum exhibit spaces aren’t all that realistic either. For some crazy reason, people really want to see the things they paid to see!
So, in a bid to balance preservation with access, museums have taken extra measures to protect their artifacts from light damage, while still allowing their visitors to comfortably view the items. Some of these measures include:
- Eliminating all natural light from windows with black-out blinds
- Eliminating excess Ultraviolet light with UV-absorbing films and filters
- Setting timer switches in galleries or display cases to turn off lights when there is no activity
- Rotating light-sensitive materials off display on a regular basis, such as every 3 months, to limit exposure time
The display of light-sensitive materials such as textiles will always be a compromise between the need to preserve the object, and the visitor’s need to see and appreciate detail. Hopefully, by witnessing the harsh visual effects of light damage—as seen in the images above—visitors might gain a bit more of an understanding as to why museums set their dimmers to low.
– Hayley Robb
Questions or Comments? Email me at firstname.lastname@example.org.
Want to hear more about the collections at NMC? Be sure to check out past blog entries featured in Amplify.
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This project has been made possible by the Government of Canada