Ed,
In theory, LEDs can be tuned to any spectral characteristics that the manufacturer wants. This means they can have 0 UV if so desired. The critical issue is what the manufacturer wants, not necessarily you the consumer. If market forces demand no UV, there will be no UV, although doing so may (or may not) raise costs. This is pretty much the same for all lamps (this is the industry term for what us commoners call bulbs). The best thing is to request from the manufacturer, not the distributor or seller, to receive spectral curves of the specific lamp or lamps under consideration. These will show the amount of UV and IR, as well as the color distribution of the light. Also request the color temperature of the lamps, as well as the color rendering index (CRI) which represents the percent of true color compared to daylight. LEDs are advancing very quickly and changes of a significant nature can occur in a year, so some diligence as a buyer is required. What was true two years ago may no longer be the case, so stayed involved. As an anecdote, the LEDs I have measured for UV did not have any, but this has only been a handful and as mentioned are only representative of those specific lamps.
Marc
American Conservation Consortium, Ltd.
4 Rockville Road
Broad Brook, CT 06016
www.conservator.com
860-386-6058
Marc A. Williams, President
MS in Art Conservation, Winterthur Museum Program
Former Chief Wooden Objects Conservator, Smithsonian Institution
Fellow, American Institute for Conservation (AIC)
From: Ed Sharpe - Archivist for SMECC
Sent: Monday, April 04, 2016 1:01 PM
To: [log in to unmask]
Subject: [MUSEUM-L] Was: UV-resistant window filmNow - LED LIGHTS and EVIL UV?
Dave or others........ what type of led strips or bulbs should we use?
I go online and see Getty using some but is backchatter on the net that LEDS can have too much UV and are EVIL!
I... am so ... confused...
Thanks for any advice
Ed Sharpe archivist for SMECC
In a message dated 4/1/2016 10:38:20 A.M. US Mountain Standard Time, [log in to unmask] writes:
Amy,
There are several considerations here.
First and foremost, while UV light is the most damaging to light sensitive collections, the rest of the light spectrum continues to accelerate photo-chemical reactions that cause permanent damage. This is why light sensitive collections such as paintings, works of art on paper, photography, textiles, etc. have to be rotated off exhibition, even if the best technology and efforts have been taken to reduce light damage. Light damage is cumulative and permanent.
Second, is the architecture of your exhibition space. Why exhibit light sensitive collections facing large windows? Are there other collections that could be in this space that are not as light sensitive, such as metals, stone, ceramics, etc.?
Third, if you do use UV filter film it is far better to mount it on a lightweight frame that can be easily mounted inside the windows and easily removed. UV film will degrade over time and will eventually lose it's filtering properties. So you will have to continue to monitor your UV levels and when there is a significant raise in your UV levels then it is time to replace the film. It would be far harder to try to peel and scrape the film off of the glass than to simply pull down a frame and replace it.
There are also some fairly lightweight sheer fabrics made for museums that will will filter the UV as well as to cut down on the amount of light coming in, that can be used.
And there are paints made for museum use with titanium dioxide in them, which absorbs UV and does not reflect it off of the walls.
Do you also have lights inside the room on the exhibits as well? You have to add those into the light damage equation and also mitigate any UV from them as well as following the appropriate light levels (foot candles) for the type of collections in the room.
The other effect of light that UV filters do not solve is the thermal (heat) energy. So if your works are inside closed-air-tight cases with glass or plexi fronts then that sunlight is heating up the interior of the cases which can either lower or raise the relative humidity, and those fluctuations can be significant in a single day between day and night. So that damage may be going on too.
You really should get a conservator in, who is well experienced with environmental issues with collections, to spend a day studying the space, taking environmental measurements, and making recommendations for best practices for the collections and with specific advice on the light issues.
If you don't have a regular conservator who you use, you can apply for grants for this kind of consultation. The IMLS encourages museums to bring in specialist consultants to help the staff care for collections, and you can contact their office to get details of what grant category and level this fits in. They are very helpful.
Cheers!
Dave
David Harvey
Senior Conservator and Museum Consultant
Los Angeles, CA USA
www.cityofangelsconservation.weebly.com
On Fri, Apr 1, 2016 at 8:41 AM, Amy Halliday <[log in to unmask]> wrote:
Hi everyone
I've recently started a job in a small college gallery with several soaring and beautiful windows, but no system in place for controlling natural light (with all the implications for heat, UV and conservation). Motorized blinds would be very expensive and interfere with the architectural aesthetics of the space, so I'm looking into getting UV-filtering film professionally fit to the inside of all of the windows and would appreciate any advice or feedback on the below from anyone who has relevant experience or conservation expertise.
Currently, the best balance of effectiveness, price and look that I've encountered is to use DN 60 from Johnson Window Films, a metallized, low reflective and neutral-looking film that "blocks 99% of harmful UV rays" and has high heat rejection. However, I'm aware that sometimes the "99%" of UV blocking is in the 325 to 380nm range, not up to 400nm, which is a gap of some concern for vulnerable items like works on paper. Does anyone have any thoughts on this, given also that with the design of the space, the windows (only on one side) are a good 20 feet from the opposite walls, and we could - ideally - combine the window film with UV-resistant plexi on framed works?
Comments and advice appreciated!
Best
Amy Halliday
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