"Bleaching" yellowed rare-earth element glass

[qball]

I understand you can remove the yellowing of certain rare-earth element glass lenses that have yellowed with age. Like the Konica 57mm/1.2.

Besides the "brightly lit" room method, I understand you can bleach it with prolonged exposure to UV light.

What kind of UV light specifically? Like a UV blacklight? Or the type of UV light you would use to sterilize things?

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[antithetic]

Couldn't you leave it in direct sunlight for a few days/weeks?

 

[qball]

Yeah, but I'd rather leave it in a closet with a light, as we have six mischievous dogs and my lens would end up as a toy.

 

[antithetic]

Oh. Didn't know mischievous dogs were in the mix. =]

I found a thread on Flickr which discusses using UV light to get rid of yellowing on the lens. Basically one poster found the yellowing decreased by using a regular UV blacklight. It's slower but safer (for humans).

Hope this helps.