> I'm working on an art project that involves illuminating large quartz
> crystals with colored LEDs.  We've discovered that UV LEDs produce a
> most beautiful effect, but we're unsure how to gauge the danger.  The
> LEDs specs say that peak power is at 405nm, (400-410nm range).  After
> quite a long time searching the web, I can't find definitive safety
> info on 405nm light.  Some suggest that it's outside of the dangerous
> UV-A range (though only barely), other sites warn of damage from all
> wavelengths less than 500nm.  Does anyone have any ideas or pointers to
> trusted resources.  Better safe than blind!

You don't say how close to the crystals you are putting the LEDs. I would
think that if you can mount the LEDs and crystals in a manner that means
people cannot look directly at the LEDs then you will be OK. Ideally have
the LED against a face of the crystal, with a suitable mask so that any UV
has to pass through the crystal to reach the viewing public. If you have any
doubts about this technique check with your local environmental monitoring
department of the council or labour department to see if they have any UV
monitoring equipment available.

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