Green Glass

Do you remember at the turn of the last century, how green, almost luminescent "uranium glass" was really popular?   A uranium glass bead, say, from a necklace can actually fog a film badge (one of those things you wear when working around radioactive materials to determine you've had enough)

In fact, a single bead of uranium glass, about the size of a good pearl, can put out about 12 microRads/hr.  Grant it, that isn't that bad.   You get about 10 microRads of background radiation just living in civilization.

I started researching other things with a home-made geiger counter circuit..   the results were interesting.   Some very old lenses I had, actually registered about 50 microRads, much more than the uranium glass!

As it turns out, from the 40's to the 80's, some lenses were crafted with Thorium, a radioactive material.   Apparently my old Pentax lens isn't a bad example of a radioactive lens.   It isn't unheard of to find 1950's and 1960's camera equipment pushing out 100 microRads/hr.

..of course, these numbers are all obtained from an Edmund Scientific DIY Geiger Kit from the Mid 90's that has been in attic storage for years.   I'm not really sure how many years in your underwear in front of the leaking microwave 100 microRads equates to but it's still something to keep in mind the next time you put that 50 year old camera to your eye.

:)