|
|
We enter the world of museums expecting to see artifacts from the past and hoping to understand their significance. We all expect museums to preserve and conserve these artifacts for time immemorial. Some artifacts need to be restored, recreating the moment of history. Others need to be preserved with just enough light to display them to the public without damaging them. With the green movement going strong, museums now face the challenge of properly illuminating artifacts, while conserving the environment.
 There is a blurry line between preserving the artifact and providing the visitor with a memorable experience. Ask any museum professional to define the difference between “preservation,” “conservation” and “restoration” and you will discover that the three terms are interrelated. Preservation in the strictest sense means protecting cultural property and prolonging its existence. Conservation means the implementation of activities—examining, documenting, treating and caring for an artifact so that it can be preserved. Restoration requires the skilled talents of artists and craftspeople to return an artifact to its original state using modern techniques.
Do these approaches sound familiar? Read any of the green literature today and you will probably see these tasks sprinkled throughout. So, in a sense, museums were well ahead of the green curve. As Kermit the Frog might say, It’s hard to be humble when you are green.
Lighting has always been inseparable from the green museum. Generally, three conservation rules dictate the following:
1) The artifact should be visible when on display but have no more light than is necessary for visibility
2) The institution must decide how much color loss in how much time is acceptable (the “light is good, light is bad” conundrum)
3) There is sensitivity for each artifact
The Canadian conservationist Stefan Michalski promulgated these three axioms and they have stuck around for well over 15 years.
Fortunately, the alphabet soup of lighting sources now provides a huge toolbox from which museums can choose. And choose they must! Starting with CFLs and running the gamut of CMH, fiber optics, HID, LED, MH, MR16, OLED, PAR, TH and UV, museums can no longer scream, “We’re exempt!” and reach for that incandescent lamp. Reaching for some of the new tools can indeed further the goals of the museum, namely preserving, conserving and restoring those precious artifacts—including Mother Earth.
THE NEW CMH
One of the sources museum lighting designers are turning to more and more is CMH. Twenty years ago, metal halides were used primarily for things like parking lots and baseball stadiums and were considered a death sentence for artifacts. Today, CMH can be delivered in smaller packages, 39 and 20 watts, offering museums considerable energy savings over the workhorse PAR36 and MR16 lamps, while greatly improving the color of the artifacts.
 Figure 1 shows a quick comparison of different light sources. Notice that the 50-W MR16 lamp and the 20-W CMH lamp have the same center beam candlepower. A museum could potentially save 30 watts a lamp or 60 percent of the energy used while gaining about 5,000 hours of life. The museum lighting designer has to choose which lamp to use before ordering the product because the lamp and ballast must match. The goal should be to minimize the light needed to see an artifact while maximizing the energy used. A point source calculation can give you the answers.
LEDs AND OLEDs
The holy grail of lighting and the green movement are LEDs and OLEDs. These sources have the backing of many lighting professionals, as well as the Department of Energy and Congress through the Energy Policy Act of 2005 and the Energy and Independence Security Act of 2007.
Evaluating LEDs requires much attention, however, especially when comparing them to traditional sources. Stephen Border of Budget Lighting, Inc., summed it up with his seven myths of LEDs:
1. LEDs last forever. While they do have a long life, like all light sources, they slowly fade over time. When the lumen output is 70 percent of initial, consider replacing the LED. That can be expensive.
2. LEDs generate no heat. While they do not generate heat in the light, they do so in the conversion of electricity to light; LEDs need heat sinks at the coupling. One study suggests that a 10-deg F rise in temperature can reduce the life by 10,000 hours.
3. LEDs produce 160 lumens per watt. Yes, on a bench test maybe, but they can lose 30-40 percent in application.
4. With LEDs, 3 watts are brighter than 1 watt. With LEDs, efficacy in lumens per watt is more important than raw watts, so higher wattage doesn’t necessarily mean brighter.
5. LEDs are not bright enough. Well, look around, they are working. And with all the research money going into the product, you’ve got to take notice.
6. LEDs cost a lot. Yes, initially they are expensive, but the return on investment can be less than two years. Watch for the initial cost to drop in the future.
7. LEDs have poor light quality. Most have a CRI of 80 or greater. And the Commission Internationale de l’Eclairage (CIE) is working on a Color Quality Scale. But in museums, it is the perception of the staff that matters.
New LED light fixtures appear everyday in the market, and the track manufacturers have begun to incorporate them into product lines. Yes, the color temperature may be a bit on the cool side, but isn’t that closer to daylight? Doesn’t this produce a truer color of the artifact than an incandescent light? And think of the energy savings. A 14-W LED fixture mounted at the ceiling 20 ft above the floor can produce more than enough light for display cases. And now, both floods and spots are available to designers.
 OLEDs are still on the experimental tables in labs. It may take a couple of years for these to get into the manufacturing chain, however when they do, OLEDs will be diffuse sources, with light output comparable to CFLs, but with much less energy and much longer life. Electroluminescent panels have been around for about 35 years, but finally the research money seems to be flowing to make the source better.
FIBER OPTICS
Soon you will see LEDs married with fiber optics. This marriage will enable lighting designers to put light inside cases while keeping the heat source, such as the LED, outside the case—all while reducing energy at the same time. These light sources will be controllable via the theatrical DMX 512 protocol, which means that dimmers will not be required, per se. Dimming will occur either via programs built into the illuminator or inexpensive programs you can load to any laptop and connect to the fixture via a standard three-pin XLR cable.
It is hard to be humble when you are green, and museums have been green for a long time. Now, thankfully, the lighting tools available to museums because of the green movement make preserving, conserving and restoring a little bit easier.
This article was adapted from the seminar entitled “Museums and A Green World: Artifacts, Energy, Light and Color” at the Light For A Green World educational conference hosted by the IES Philadelphia Section in September 2008.
|
