Re: Yellowing of radioactive lens elements....Re: [OM] 55/1.2

[Mark Marr-Lyon]

> There is an absence of any evidence that I have seen in all this thread
> which demonstrates ionizing radiation or radioactive decay to be the
> causative mechanism for the color change.  That rare earths change the
> color of glass is well known. 

True, but were the lenses yellow when made?  I wouldn't think so, since that wouldn't seem to be a big selling point.  If they weren't yellow originally, then presumably they don't yellow over the course of days or months, but take years or decades to really turn yellow.  What kind of delayed chemical reactions can take place to cause yellowing over such a time scale?  I guess I still would be extremely surprised if the yellowing was not caused by the radiation, even if indirectly like a daughter product or reaction with one.

> I would like to know the exact radiation 
> intensity per gram in this glass.  Would be surprised if it was within 
> an order of magnitude of the art glasses which used uranium, thorium, 
> etc. to effect coloration.

It's been a while, but I think that I measured the (beta and gamma) radioactivity of my 50/1.4 to be around 3000 to 4000 counts/min, or about 1000 times background, with the Geiger tube right next to the glass.  This was approximately the radioactivity level of some orange Fiestaware we had too.  The 55/1.2 was a bit higher, since there's 2 elements, and one is pretty large.

I'm not terribly optimistic about the UV cure working either, but I haven't tried it so it just might work. 

Mark