Dear Christine:

I have been investigating halogen lights used in museum exhibits with a UV
meter.  So far, I find the UV levels produced vary, but in many exhibits
seem to range from 80-150 microWatts per lumen (recommended levels are under
75 mW/l).  I recommend that museums look at the manufacturer's information
before purchasing their bulbs. (As you have done.) Usually there is a chart
of the energy spectrum showing the areas in which the bulbs produce
radiation.  Nowadays, this varies enormously, even among fluorescent bulbs.
(As conservators, we can no longer recommend general types of bulbs with
complete certainty. Technology has made our job more difficult.)

3M produces a variety of film materials that filter different parts of the
energy spectrum.  They are located in St. Paul, MN.  Their general number is
612-73-1110.  For product information they have a toll-free number,
800-364-3577.

A simple way to use a UV filtering film material over a spot light:  stretch
the material in an embroidery hoop and mount the hoop in front of the spot
light's can (the metal canister that holds the bulb).  Allow air space so
the film does not melt.

We will probably feature an article on light options in an upcoming issue of
The Collections Care Network.  I will try to let you know when it is
published.  (The Collections Care Network is a technical bulletin written
for the small to medium sized museum covering a variety of preservation and
collections care issues.  It is published 6 times per year.  It is provided
free to UMCA members and museums in Iowa, North Dakota, South Dakota and
Minnesota.  It is available at $12/year subscription from:  Field Services
Program, The Upper Midwest Conservation Association (UMCA), 2400 3rd Ave.
S., Minneapolis, MN 55404. Our next issue features the use of wood stoves in
living history museums.)

Helen Alten
Field Services Director
The Upper Midwest Conservation Association
2400 3rd Avenue S.
Minneapolis, MN 55404
612-870-3120
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At 06:20 PM 12/6/96 -0500, you wrote:
>Hello all:
>
>I am writing to clear up some confusion about the UV output of
>halogen light bulbs.
>
>I had an inquiry from a friend who runs a small, but  respectable,
>private quilt museum behind her antique shop in a small town near
>here.  She really does a good job at maintaining high standards and
>is conserned about conservation, etc.  She called to tell me that a
>visitor this morning told her she needs filters on her halogen flood
>lights in the museum and that she was ruining her quilts.   She
>wanted to know what I knew about halogen.
>
>My initial response to her need for filters was "nonsense." Her flood
>lights are about 20 ft. from the textiles on exhibit (so heat is not
>an issue), and I'd say the light level is about 10 footcandles.  The
>lights are only on when there is a visitor to her museum room, and
>she rotates her exhibits every few months.  But then I thought about
>it and curiosity made me look it up in some reference materials and I
>discovered from a chart that tungsten halogen bulbs produce as much UV
>as fluorescent bulbs.  I also checked the Consdist List archives
>(CoOL) and could find scant information there, but what I did see
>hinted that halogen bulbs might actually be better than fluorescent
>for UV output.  The Museum-L archives had nil (that I could find) on
>this topic.
>
>So....
>1.  Do tungsten halogen bulbs put out more UV than regular
>incandescent bulbs?  As much as UV as fluorescent?
>2.  Are all halogen bulbs tungsten bulbs?  If there is such as thing
>as non-tungsten, are they better or worse?
>3.  Can anyone recommend a cheap source for UV filters?
>
>If she does need filters, perhaps it would be better and cheaper to
>just replace the halogen flood bulbs with regular incandescent flood
>bulbs.
>
>Can anyone help?  Thanks!
>
>Christine Mouw
>Assistant Curator
>Herbert Hoover Presidential Library-Museum
>West Branch,  IA  52358
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>
>