[NHCOLL-L:3417] Re: light levels for mineral specimens

[Victoria Book]

Hi Cherry,

Lighting is a complicated issue that depends on your specimens and 
resources.  If you can, all ultra-violet light should be eliminated (if 
a UV reaction is part of the exhibit then that is a different can of 
worms) using low UV emiting lamps (bulbs), or filtering glass or plexi. 
  As you mentioned, many minerals do not respond to light and the light 
level is not specified (but it probably should be decided relative to 
neighboring exhibits).  As Kris noted, adhesives and consolidants may 
age poorly with higher light levels.

Light sensitive minerals should be lit as low and seldom as possible 
(usually 50 lux/5 footcandles) in order to keep their color and 
translucently.  Light damage for most minerals (and all organic 
materials) is cumulative, so less light is better no matter how you do 
it.  If you can turn off lights or close blinds when the exhibit is 
closed, or do something fancier with motion detectors, that is even 
better.

Two points for further discussion: 1.  There is evidence that, for many 
objects, an anoxic environment will dramatically slow fading.  I don't 
know if this applies to any minerals but as anoxic environments are 
becoming cheaper and easier to build it is worth looking into.  2.  
There are ways to make it look brighter while maintaining "low" light 
levels.  The eye takes some time to adjust to darker areas, so if you 
can have progressively darker areas, by the time the viewer gets to the 
50 lux area, night-vision has kicked in and the viewer can see fine 
(disclaimer: this is age-dependent to a degree).  This is one 
justification for lower light levels overall (200-300 lux or less) even 
for specimens that aren't light sensitive.

Do you know if your specimens are light sensitive?  I can recommend 
some articles if you'd like more information.

Good luck,
Victoria

Victoria Book
Conservator
Sam Noble Oklahoma Museum of Natural History
University of Oklahoma
2401 Chautauqua Avenue
Norman, Oklahoma   73072-7029
phone 405.325.5163
fax 405.325.7699
www.snomnh.ou.edu


On Apr 26, 2007, at 11:08 AM, Cherry Johnson wrote:

>
> Hi All,
> Could anyone advise as to preferred light levels for exhibiting 
> minerals. 
> Obviously, there are some that can be really damaged by light and some 
> not so much.  Any input would be helpful.
> Thanks,
> Cherry
>  
>  
>  
> Cherry Johnson
> Collections Manager
> Weinman Mineral Museum
> PO Box 3663
> Cartersville, GA  30120
> 770-386-0576 x 405
> 770-386-0600 fax
>  
>
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