One of the things I like best about this list is that when I need an answer, someone else writes in and asks the question; as in this case. I'm in the process of writing a grant application that involves changing the office-style flourescent light fixtures in one of our galleries to a system better suited to museum exhibits and safer for the artifacts. It looks like there is also something better than the low powered halogens that we have in our upstairs gallery.
Thank you for the comments. I now have some good leads.
Jerrie
Jerrie Clarke, Director
Sheldon Museum
PO Box 13
Haines, AK 99827
www.sheldonmuseum.org
(907) 766-2366
fax: (907) 766-2368
Marc A Williams <[log in to unmask]> wrote:
Résumé / AbstractCurrently, the highest color rendering index (CRI) value obtained in commercially available LED devices is around 90. This falls short of the CRI values typical for incandescent lamps (defined at 100). Similarly, the commercially available LEDs for higher color temperature have CRI values of 65-85, well below the theoretical maximum of 100. New phosphor blends are proposed for use with LED chips emitting in the 350-450 nm range. The application of such blends can afford CRI values greater than 95, over the entire range of color temperatures of interest for general illumination (2500K -8000K). In some cases, the CRI values approach the theoretical maximum of 100. LED based lamps with a steady state performance of 23 LPW and 25 lumens per chip at 3000K, with a general CRI (Ra) of 97 and a mean CRI (R1-R14) of 96 are demonstrated.
Pulled from a quick Google search. Current CRIs for LEDs are lower than other options in the daylight (5000-6500K) range. Thus, they are probably not ideal for museum lighting. Note from above that new phosphors are proposed in the 350-450 nm range, that will bring CRI up into the 90s, or equivalent with other sources. HOWEVER, 350-400 nm is in the UV range, so these new light sources will probably emit UV light!! Stay tuned....
Marc
American Conservation Consortium, Ltd.
4 Rockville Road
Broad Brook, CT 06016
www.conservator.com
860-386-6058
*Collections Preservation Consultation
*Conservation Assessments & Surveys
*Low-Tech Environmental Control
*Moisture Management Solutions
*Collections in Historic Structures
*Conservation Treatment of:
Furniture
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Horse-Drawn Vehicles
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Marc A. Williams, President
MS in Art Conservation, Winterthur Museum Program
Former Chief Wooden Object Conservator, Smithsonian Institution
Fellow, American Institute for Conservation (AIC)
----- Original Message -----
From: Paul Fritz
To: [log in to unmask]
Sent: Friday, June 01, 2007 11:18 AM
Subject: Re: [MUSEUM-L] Museum lighting
Another aspect to remember.
I can't remember off-hand who I had a good email conversation with regarding LEDs, but he mentioned to me that the CRI was an important aspect worth considering. This is the measurement of how light renders the color of objects. The wrong color light will make objects look weird (think of a blue light on a white surface will make the white surface blue).
There are a few LED manufacturers (Luxeon) that make LEDs with a warmer color temp, but I really don't know what the CRI for them is. I have used the bright white Luxeons (not the warmer color) in an exhibit with great success, but I was illuminating a sky, so the trace blueness of the light made it look good.
I'd recommend trying an example of several lamps to find the one that would best approximate what you are looking for.
Oh, and to echo Marc, from my understanding, light damage is cumulative. Any time an object is exposed, it adds to the damage, so these lamps really only delay the damage by removing unnecessary UV. The best thing to do is limit the overall illumination to the lowest level possible.
Paul Fritz
--
Paul C. Fritz
Pamplin Historical Park & the National Museum of the Civil War Soldier
6125 Boydton Plank Road
Petersburg, VA 23803
(804) 861-2408 -- Tel
(804) 861-2820 -- fax
Visit us at
www.PamplinPark.org
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========================================================= Important Subscriber Information: The Museum-L FAQ file is located at http://www.finalchapter.com/museum-l-faq/ . You may obtain detailed information about the listserv commands by sending a one line e-mail message to [log in to unmask] . The body of the message should read "help" (without the quotes). If you decide to leave Museum-L, please send a one line e-mail message to [log in to unmask] . The body of the message should read "Signoff Museum-L" (without the quotes).
Jerrie Clarke
Director
Sheldon Museum
PO Box 269
Haines, AK 99827
(907) 766-2366
fax: (907) 766-2368
www.sheldonmuseum.org
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