Originally posted by stevebrot I think you are probably on to something there. I did a little research on radiation-induced color in quartz and glass a few weeks ago and it may be that the heat or IR from the sun/lamp may be doing the actual work.
Google: "radiation glass color centers"
Steve
I will google that. Very interesting topic.
I have also thought about to try IR for deyellowing, I allready have a large IR bulb for some reason which I can try. But than again, internet is writing about how UV and UV alone is bleaching these lenses, and if you take a brief look at many LED spectrums of "warm white" or "cool white" LED lights (probably JANSJÖ is one of them), you can see that IR radiation from those LEDs is not great, I would say practically non existing. Also is the case with true UV portion of spectrum but the crossing between UV and B is much steeper than it is from IR-NIR and R.
This topic would definitely make a great and interesting obscure scientific paper, finding out why that IKEA light bleaches the lens and why is UV better for bleaching and if it is the UV that bleaches the lens. Sun is probably the best way to bleach the lens because of the broadest wavelenghts you can own but it is slow and dependant on weather, especially in this winter months.
Also, it would be cool to find out why the yellowing is happening at the first place (and I don't mean scientific by quoting other peoples posts from various other forums), some people say that the glue in the glass is just aging and UV bleaches it, some people say that the glass and/or glue is changing structure as it is reacting with radiation from thorium and other elements in thorium decay chain which are responsible for beta and gamma going through the rear element.
And a brief look at this thing :
Radiation induced color centers in silica glasses of different OH content says that some glass does react with gamma, although I have no idea what this paper is really about, it just makes me think. Fact is that older the lens, the greater is the yellowing. My lens has a serial number 2066114 and was much more yellow than I saw on images of 3000000+ serial number lenses. And I found some paper saying that the older the thorium glass element is, more gamma and beta it emits, but that output gets stable over time, it doesn't go up forever. So if you have a brand new thorium glass element made in the factory, it would probably be outputing pure alpha radiation, and over time as many daughter decay element isotopes begin to appear in glass, some more stable than the other, which emit gamma and beta they could potentially induce the yellowing of the glass via those gamma decaying isotopes. Until someone makes a valid scientific research we can just keep bleaching the lens using sun, blacklights, JANSJÖ's, and UV LEDs. But I am very interested in the physics and chemistry behind that whole process, it just tickles my inner scientist to question that.