[Leica] OT: Fixing radioactive lenses

[len-1 at comcast.net (Leonard Taupier)]

I have an old Pentax 50/1.4 Super Takumar that has, over time,  
yellowed due to one of the elements containing Thorium, a mildly  
radioactive element. The addition of thorium makes a very high  
refractive index glass, and a very good lens. This lens is probably  
one of the most famous lenses with this element but I'm sure there  
were more.

The fix for removing the yellow cast to the lens is to expose it to a  
UV source like sunlight or a UV light for a week or more. I have been  
putting the lens in a window during the day and exposed to a black  
light at night.

My question is concerning the glass used in my windows. They are made  
of high E glass and have an air space between the double panes. I  
know high E glass is supposed to suppress  Infra Red but I see no  
info on if it passes Ultra Violet which is at the opposite end of the  
light spectrum. Does anybody know?

Thanks,
Len