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clear yellow lenses
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PostPosted: Wed Nov 13, 2013 4:06 pm    Post subject: clear yellow lenses Reply with quote
http://nortega.com/fastest-tool-to-clear-yellowed-thorium-lenses/


PostPosted: Wed Nov 13, 2013 4:29 pm    Post subject: Reply with quote
Although I know that guy, I sincerely doubt that. No LED lamp "puts out"
UV light, except it has an UV LED built in!!


PostPosted: Wed Nov 13, 2013 4:32 pm    Post subject: Reply with quote
I have that Ikea LED lamp and I can confirm that it works fast for the initial clearing of yellowed lenses. However, it does not seem to clear them more than about 90%—it only takes a few hours to go to about 80% clear, about 12 hours to 90%, but then even an additional week of exposure 24h a day does not do anything. So sunlight is still the only reasonable way I've found to get lenses perfectly clear.

I did this to about 10 lenses and I took pictures of some of them during the de-yellowing process, so despite initial doubts I can confirm it does work.

(Of course the IKEA LED is not magic; other LED lamps can be used as well, I've tried a couple of different ones with similar results. Interestingly UV LEDs do not seem to be much better than regular white LEDs.)


PostPosted: Wed Nov 13, 2013 4:41 pm    Post subject: Reply with quote
Then it is not the UV that does the curing but the blue content possibly?

Thanks for sharing your experience!


PostPosted: Wed Nov 13, 2013 4:54 pm    Post subject: Reply with quote
kds315* wrote:
Then it is not the UV that does the curing but the blue content possibly?

Thanks for sharing your experience!


I have had the same experience as arkku - probably I tried after reading about that from him.
When I tried, I read a large number of articles about leds emitting uv light, and many sources - whose attendibility I could not verify, to be honest - reported that many low quality leds (as the one in that famous ikea lamp) tend to emit a certain amount of UV light.

As I said I didn't have any way to verify these pieces of info, and I'm sure you know much more about this topic than the ones that wrote (or cut and pasted) the articles I read, but I think it was worth mentioning that.

Anyway, in my opinion, the important thing is that, up to a certain point, it works good and fast.


PostPosted: Wed Nov 13, 2013 6:27 pm    Post subject: Reply with quote
I sold my S-M-C. 1,4/50 because it's yellowed. It returned again and again.

The process that seems to work for me, was to put the lens under UV light and clear it. After, once a week leave the lens under UV for 24 hs., but it was so hardly.

No yellowed lenses for me again.


PostPosted: Wed Nov 13, 2013 6:33 pm    Post subject: Reply with quote
kds315* wrote:
Then it is not the UV that does the curing but the blue content possibly?

Thanks for sharing your experience!


So, a dark blue cellophane added to the diode should work fine too?


PostPosted: Thu Nov 14, 2013 1:33 am    Post subject: Reply with quote
I will soon be purchasing a very strong UV light for my business. It will be used for UV cure finishes.I have one very yellowed lens that I will expose to this light.


PostPosted: Thu Nov 14, 2013 8:41 am    Post subject: Reply with quote
DR.JUAN wrote:
So, a dark blue cellophane added to the diode should work fine too?


That should make no difference. It would just filter out the non-blue wavelengths, but it won't magically add more blue photons


PostPosted: Thu Nov 14, 2013 10:53 pm    Post subject: Reply with quote
spoilerhead wrote:
DR.JUAN wrote:
So, a dark blue cellophane added to the diode should work fine too?


That should make no difference. It would just filter out the non-blue wavelengths, but it won't magically add more blue photons


Thank you, very much.


PostPosted: Sun Nov 17, 2013 4:56 pm    Post subject: Reply with quote
Arkku wrote:
I have that Ikea LED lamp and I can confirm that it works fast for the initial clearing of yellowed lenses. However, it does not seem to clear them more than about 90%—it only takes a few hours to go to about 80% clear, about 12 hours to 90%, but then even an additional week of exposure 24h a day does not do anything. So sunlight is still the only reasonable way I've found to get lenses perfectly clear.


It makes sense - glass typically absorbs UV so depending on wavelength the UV can go only so deep. I suspect that disassembling rear group and irradiating yellow element directly from both side will do the trick.
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