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GeneralLight Sensitivity

16th Apr 2012 23:08 UTCTony H. Gill Expert

Hi All

I was wondering if it is possible to protect and display a specimen that may be sensitive to light. I was think some form of localised protection, perhaps on the cabinet glass protecting the specimen from direct Sunlight or a more localised protection - perhaps a specialised dome over the specimen itself? Anybody have any ideas?

Thanks

Tony

17th Apr 2012 00:37 UTCAlfredo Petrov Manager

Tony, I'd say that "light protection" and "display cabinet" are two mutually exclusive concepts. If you shade it, you're just slowing down the damage, not stopping it. Some museums keep their proustites in a glass case completely covered with a black board on a hinge, so the rocks are in complete darkness (except for any light leaking in around the edges) except for the moments when the lid is raised. Make the lid thick and heavy, to discourage viewers from holding it open too long :-D

I've sometimes wondered whether one could tune the colours of one's illumination. We know that realgar is damaged mainly by green light, so theoretically if we illuminated its case with only red light it should look nice and be safe. Does any similar research exist for other light-sensitive species?

17th Apr 2012 15:28 UTCPeter Lyckberg Expert

The deep orange Urulga Topaz crystals kept in the BM London do fade rather rapidly in "sunlight" , (well read as any intense photon bombardment) and they have fitted thick paper covers and are kept in dark closed drawers at all times. A forth crystal was exchanged with the Sorbonne Museum (Université P & M Curie) in Paris. There the thick glass was designed (thickness, type) to filter enough of the UV and higher energies from the externally placed spots. Measurements and calculations were made to ensure no fading of the topaz.

17th Apr 2012 17:50 UTCHolger Klapproth

Most photo reactions need a certain amount of energy to get started. Therefore UV, blue and green light, which transfer a larger amount of energy are more damaging than red light. Hence the red light in when you develop paper photographs. But most minerals do not look very well when illuminated with red light. Most plastic cases will already filter out a large amount of the UV - but than alone may not protect your minerals. I would recommend to keep them in the dark. Only in cases where it is known that UV causes the damage (some fluorites for example) a polystyrene cover may be of help. but if minerals also do not like visible light - I fear they must be kept well hidden in the dark.

17th Apr 2012 22:50 UTCTony H. Gill Expert

Thanks All,

Was thinking some form of clear filter would do it whilst allowing you to see the specimen.

Thanks

Tony

17th Apr 2012 22:59 UTCJolyon Ralph Founder

Tony

That would work for minerals which were UV sensitive - unfortunately many minerals are sensitive to visible wavelengths.

Joylon

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