[NHCOLL-L:2138] RE: lighting in exhibit halls

[Dan Brooks]

Greetings all

Per the request of some of you, below are the great responses i received re:  my query on lighting in our new African Hall.  Kind thanks for all of your great help!


-------------------------------------
Daniel M. Brooks, Ph.D.
Curator of Vertebrate Zoology
Houston Museum of Natural Science
1 Herman Circle
Houston, TX 77030-1799

dbrooks at hmns.org

PH- 713-639-4776
FAX- 713-639-4767



Posted to: NH-Coll. List-serv 11/12/03

Greetings all
We're in the process of re-doing our African Wildlife Hall.  The lighting fellow we've contracted wants to use Halogens, and says they won't really harm the specimens as much as any other bulb (except for fluorescents which he says is worse).  We're going to put some filters to cover the overhead lights, but I'd like to get some feedback from the group on how harmful different types of lights are....... I've even heard from one school that direct sunlight is the only thing that will cause fading in your mammals and birds......
any feedback would be most appreciated!
kind thanks
dan brooks 


Dear Dr Brooks,
I'm no expert, but my understanding is that the higher the color temperature of light, the more damage it does. This is because shorter wavelengths are more energetic or something. Beyond white light lies UV, which does the real damage. Fluorescents have a higher color temperature than incandescents for a given wattage, and halogens even higher. Highest of all is photographic flash light, which is as white as direct sunlight.
Squid fishermen in the Japan Sea have a very high incidence of skin cancer as they work all night under ship-long festoons of 1000-watt arc lamps that attract the squid. There is enough UV in these relatively low-color-temperature incandescent lamps to tan these guys black. How much more so, then, in a halogen lamp?
Regards,
PC. 
Paul Callomon
Collections Manager
Malacology, Invertebrate Paleontology and General Invertebrates
Department of Malacology
Academy of Natural Sciences
1900 Parkway, Philadelphia PA 19103-1195, USA
Secretary, American Malacological Society


I think one of the biggest concerns with halogen lighting is the fire hazard that contact with the bulb poses.  Will your exhibits contain dried natural grasses?  Will lighting be overhead or below/level with the exhibit?
Halogen lighting produces much heat, and fires caused by these bulbs have occured frequently, especially in residential situations.
    As far as fading is concerned, I would assume that the halogen lighting would be fine, though I am no expert on that.
Rick


Hello Dan,
This is a very broad topic and cannot be answered completely in this way.
What I can tell you is that halogens will do just fine, since they are low in ultra violet content (the most damaging wavelengths of light energy) and can be tailored to almost any need (colour, size, brightness, etc.).  You
still need to be wary of the intensity and duration of illumination, as any kind of light will cause fading, embrittlement, yellowing, and other photochemical damage.  You want to limit both of these, intensity and duration, to the minimum necessary for your purposes.  Keep light intensity to under 50 lux if possible.  If not possible, reduce the length of exposure by using motion sensors or visitor-activated switches.  One last comment about halogens... the ballasts and bulbs run extremely hot, so you need to make sure you have air circulation around them and that they are not placed too close to specimens.
As for fluorescents, they have their place too.  They give nice overall illumination, can be tailored to produce different colours of light (some reproduce daylight quite nicely) and can be much cheaper to use.  You can now get fluorescents with very low UV content, but you must specify.
Otherwise you will probably need a UV filtering sleeve or panel to reduce the amount of UV that falls on the specimens.  Again, the rule is minimum intensity and duration to produce the required effect.
Good luck, and remember, whoever told you that only sunlight will fade mammals and birds, cannot be trusted for accurate information. 
Kasey Brewer
Conservator
Royal Saskatchewan Museum
2340 Albert Street
Regina, Saskatchewan  S4P 3V7


Dan,
Not being a true "Museum person" or "conservator" I do not speak with great authority. However, it is my understanding that any source of UV radiation will cause fading depending on intensity of the UV radiation and the length of time. Sunlight is a high source of UV radiation. The library at
the Carnegie Museum of natural History had UV filters on the windows and I lobbied to have them put on the windows in the Section of Mollusks. We were experiencing fading of the bindings of books as well as changes in the finish on cabinets that were sun exposed as opposed to those that were not sun exposed. Tim Pearce, our new curator, agreed and was able to get the filters as part of some renovations that were being done.
Flourescent lights are a big source of UV radiation, incandescent light much less so. We put UV filters over all the flour. tubes in our Section.  I was not sure about halogen lights but a search on the internet found several people who claimed that some halogen lights are a source of UV radiation though they did not quantitate the amount. I would either check with the manufactrer of the bulbs and get a copy of the light spectrum of the bulbs in question and see how much of the light produced falls in the UV region. Alternately, I would request UV filters to be used. Remember, UV filters are not a permanent solution and need to be changed every several years depending on the intensity of UV rediation that they are blocking.
Hope this helps.
Regards,
Charlie
Charlie Sturm, Jr
Research Associate - Section of Mollusks
Carnegie Museum of Natural History
Pittsburgh, PA, USA


Dear Dan,
There are several good references available.  One of them is Conservation Concerns   A Guide for Collectors and Curators  ed. Konstanze Bachmann, Smithsonian Institution Press 1992.  ISBN 1-56098-174-1.
I will try to paraphrase and summarize some of the things mentioned in this book.
		Principals of Storage  K. Bachmann and R.A. Rushfield  pp 6-7
...Ultraviolet light (UV) is extremely damaging...Recommendations for light levels or general background illumination are 5 footcandles (50 lux) for highly sensitive objects, usually of organic nature...Fluorescent tubes and/or tungstan-halogen lamps...must be covered by filters...especially if these lights are used as the primary light source...Excessive use of incandescent lamps should be avoided ...generate heat...bulbs and lighting tubes are located sufficient distances from objects to avoid fires hazards as well as to prevent deterioration of materials.
		Warning Signs:  When Textiles Need Conservation  L.A. Commoner  p 86
...Control length of exposure to light...Control intensity of light...5-10 footcandles (50-100 lux)...evenly distributed...Elimination or filtration of all sources of ultraviolet radiation...Low-UV-emission fluorescent bulbs can be used without...sleeves...Standard fluorescent bulbs...fitted with sleeves...changed when they show signs of physical damage...Incandescent lamps provide the safest form of visible light.  Tungstan halogen lamps produce a slightly higher, more damaging light...UV-filtering lenses and lamps are preferable under conditions of extended exhibition.  "Warm," low color-temperature fluorescent lamps are prefered to "cool," high color-temperature fluorescent lamps since they have less damaging visible radiation.  Full spectrum daylight fluorescent lamps produce a high amount of damaging visible light...Natural daylight, with the highest component of blue light, is the most damaging form of visible light...
		Composite Objects:  Materials and Storage Conditions  V.R. Hunt  p 133
Recommendations for Light and Temperature
...animal glue...fur, feathers, hair...skins, leather...5 footcandles 65ºF ..horn, bone, antler...15 footcandles 65ºF
		You may also want to look in the book  Guide to Environmental Protection of Collections  Barbara Appelbaum.  Sound View Press, 1991.  ISBN 0-932087-16-7.
The Canadian Conservation Intitute has publishe numerous CCI Notes.  Note numbers 2/1, 2/2, 2/5, 2/6, 8/2, 8/3, 8/4.  Their website is www.cci-icc.gc.ca
Hope this helps.
Leslie L. Skibinski 
Collection Manager of Mollusks
Delaware Museum of Natural History
P.O. Box 3937
4840 Kennett Pike
Wilmington, DE  19807


The biggest problem with halogen is heat, which can cause havoc on your environmental controls.  Just be aware of this potential problem.
Susan
Susan Fishman-Armstrong
Laboratory Coordinator
Antonio J. Waring, Jr. Archaeological Laboratory
1600 Maple Street, Carrollton, GA 30118


I'm not an expert at this , but from my experience looking into lighting for our diorama exhibits, here are some general thoughts.
		The amount of light is important. The more light, the more fading over time, so use as little light as you can get by with.  Uv is the most damaging in general, and since we can't see it, always try to reduce it.
Tungsten bulbs, including halogens, produce significant amounts of UV light. In the past, fluorsecents used to produce large amounts of UV, but newer bulbs have significantly reduced the amounts. The standard 4' tubes come in a wide variety of types with different color spectrums and UV outputs. There are also inexpensive plastic filters available for them the cut almost all the UV.
		Halogens produce and very intense light that can be very dramatic, but they also produce a lot of heat and will require expensive glass filters. I would carefully look at the technical data on every lamp you are considering, to make sure its UV output is very low. Over time, filters tend to get broken, lost or forgotten.
Don Luce
Curator of Exhibits
Bell Museum of Natural History
10 Church St. SE
University of Minnesota
Minneapolis, MN 55455


1) All light can cause damage
2) The amount of damage is proportionate to:
   a) the intensity of the light
   b) the duration of the light
   c) the frequency of the light
3) Most people don't get the frequency part
   	a) UV filters don't prevent damage
   	b) blue visible light is also harmful
				* halogen and florescents have more blue/UV
		c) infrared (heat) can also be harmful
		    	* incandescent and halogen have more infrared
4) If you want to mitigate light damage:
   1) decrease duration and intensity!!!
   2) light the object, not the space!
   3) control UV (and excess infrared)