LED lights in exhibition cases

In Conservation DistList Instance: 17:2 Thursday, June 19, 2003,
Karen Potje <kpotje [at] cca__qc__ca> writes

>...  Is information about the
>UV content of white LEDs available?  Is it possible to control the
>light levels and ensure that they remain at a steady 50 lux  over
>the course of a long (8 month) exhibition? Do LED lights start out
>bright and then get dimmer over time? ...

In 1999 a large hallway in Henry Ford Museum was renovated to
include the display of artifacts in wall niches that were original
to the 1926 building. The addition of appropriate lighting to the
existing wall niches posed a unique problem because the niches could
not be modified. The idea to experiment with the use of Light
Emitting Diodes (LED's) was proposed by one of our facilities
project managers. He recalled having read an article in the February
2001 edition of Scientific American entitled "In pursuit of the
Ultimate Lamp" by Craford, Holonyak and Kish that referenced the use
of LED's in a display of "Beatles" costumes at the Metropolitan
Museum of Art.

For our project we hired Impact Electric impact [at] tir__com to design
lights for use in our wall niches. They purchased custom-made lights
from LEDtronics, Inc.  <URL:http://www.ledtronics.com/>. The first
batch of lights consisted of a mixture of white and yellow LED's
used in combination to produce an aesthetically acceptable color.
The light bulbs were configured for use in existing screw-based
sockets. The bulbs (part #R-123-OYW-120AS) were purchased for $250
each and were guaranteed to last for 2 years. Within the first year
all of the bulbs grew dim, malfunctioned and "blew out".

We had also utilized the same lights in a second exhibit gallery
comprised of three large exhibition cases. The lights in these cases
also malfunctioned and "blew out" within the first year.

The supplier recently provided replacement bulbs for both exhibits
along with the following explanation: "the combination of white and
yellow LED's drew different amperages which caused the LED's to
short each other out". The replacement bulbs part #R-30-123-2IW
120AS utilize LED's that are homogeneous in color and provide a much
improved color for the display of artifacts. We are hopeful that
their longevity has also been improved. Despite the manufacturers
claim that LED lights do not generate heat, they do become warm in
an enclosed space. Recently I conducted an elementary test to
determine the heat gain in a small exhibition case. I placed a
hygrothermograph in a small vitrine in which a screw based socket
bulb was located.  After a few weeks there was no discernible heat
gain in the case interior versus the room interior. I was unable to
detect the presence of any UV radiation using a Crawford UV monitor.

The second type of LED bulb that we have utilized was purchased was
from Color Kinetics <URL:http://pro.colorkinetics.com/products/> in
2001.

The system was used in a very large exhibition case for the display
of textiles it included a programmable timer and color change
capability. The first set of lights was purchased through a
contractor. Shortly after installation oil began to leak from the
lamp housing. The manufacturer informed us that this particular
model was no longer in production. After some negotiation our
exhibit manager obtained replacements. Thus far the replacement
lights model #C-200 from have been reliable and have caused no
significant heat gain to the case interior. There is also no
measurable UV emittance.

Mary M. Fahey
Head of Preservation/Chief Conservator
Henry Ford Museum and Greenfield Village at The Henry Ford
313-982-6072


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                  Conservation DistList Instance 17:34
                Distributed: Thursday, October 16, 2003
                       Message Id: cdl-17-34-002
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