Lighting the Rooms Where Your Art and Memorabilia are Displayed
How light affects art and artifacts is one of the most difficult preservation concepts to grasp. As a result, a lot of misconceptions about how to avoid light damage have arisen. In this post, I hope to simplify information about light damage and how to avoid it. I will discuss four factors you should consider when dealing with how light affects your collection items:
- Sensitivity (susceptibility of items to light damage)
- The light spectrum (infrared, visible, and ultraviolet light)
- Light levels (the brightness of the light)
- Duration of lighting time (length of exposure time)
When we speak of damage caused by light we usually talk about fading, but light can also cause darkening and embrittlement. If you’ve ever let a newspaper sit on your porch for a couple of days, you’ve seen the paper darken. If your children have left plastic toys in the yard for several days, you’ve seen the toys not only fade but also become brittle.
Different kinds of artifacts are affected differently and some aren’t affected at all. There’s nothing you can do to improve an item’s sensitivity to light, but knowing how sensitive an item may be will help you determine how much exposure to allow.
The caveat to this is that it’s educated guesswork and not always accurate. For example, textiles are almost always considered highly susceptible to light damage, but I once saw a 19th century shawl that had been on exhibit for 25 years with no discernible light damage. At another time, I determined a document to be of medium sensitivity and safe to exhibit for a year in low light, but within a month it became apparent that the ink was fading and we had to remove the item from the exhibit. So this is not an exact science. When in doubt, perhaps the best rule of thumb is to assume the lowest possible sensitivity and treat the item accordingly.*
The Light Spectrum
The light spectrum looks something like this.
The infrared portion of the spectrum is commonly thought of as heat. Heat will be discussed in another post about environment so, for now, I’ll just say that as temperature rises, the deterioration rate of items increases. Where possible, use lights that do not increase the temperature around items you have on display.
Ultraviolet light is invisible to the naked eye but will, nevertheless, cause damage. The risk of light damage to objects can be reduced by filtering out UV light. This effect varies depending on the object’s susceptibility to light damage. Filtering UV light on objects with a high susceptibility to light damage may reduce the time to noticeable damage by a factor of about 2%. For items with a low susceptibility to light damage, time to noticeable damage can be increased by a factor much, much greater than that. UV light can be filtered in at least three ways;
- Buy UV filtered or low UV light bulbs
- Apply UV filtering film to windows
- Request UV filtering glass for your framed items
Visible light helps us see things. It illuminates objects and reflects back to our eyes the colors of the rainbow: red, orange, yellow, green, blue, indigo, and violet. This part of the spectrum does cause fading to occur but filtering out this light prevents us from seeing. It’s a catch-22 in which we choose between protecting our objects from light damage and seeing the objects we’re trying to protect. However, while we may not be able to filter out the visible light, we can reduce the risk of damage by reducing light levels and the amount of time items spend under light.
The brightness of light can be measured in foot-candles. Unless you have a light meter, you won’t be able to measure the foot-candle levels in your home, but you can estimate by knowing common foot-candle levels you experience in everyday life.
By reducing the light levels in your home, you will increase the time to noticeable damage of displayed items. You can reduce light levels by keeping drapes closed in the day, by purchasing bulbs with lower brightness, or by using a dimmer switch to keep lights low when brightness isn’t needed.
The less time an item spends under light, the lower the risk of light damage. By cutting light exposure time in half, you will double the time to noticeable damage. By keeping an item in an archival storage box, you completely reduce the risk of light damage.
To Sum Up
To reduce the risk of light damage to your personal memorabilia and artifacts, start by making your best educated guess about the sensitivity of your items to light. Use this information to determine whether you want to incur the risk of light damage by putting the item on display.
For items that are on display, filter UV light where possible. By doing this, you can increase the amount of time an item can be displayed before noticeable damage occurs.
Reduce the light levels in rooms where items are on display to reduce the effects of visible light on the items
The effects of visible light can also be reduced by reducing the amount of time items spend under light.
* It is interesting to note that the longer an item is exposed to light, the lower it’s susceptibility becomes. This is not necessarily a positive thing; another way to say it is that the more light damaged an item becomes, the less likely it is to incur more light damage. I once consulted with someone that had a large quilt prominently displayed in a very sunlit room. The quilt had faded considerably and they were considering displaying the other side, which was identical to the displayed side but had not faded at all. I counseled them to leave it as it was; the faded side had reached a point of low susceptibility to more damage and they would be able to preserve the other side by leaving it against the wall and out of the light.