In one of our catalogs we made joking reference to some new beads made with "...glow in the dark, uranium glass...." They were a beautiful yellow-green color, and, of course, they didn't glow in the dark. But, it got us to thinking, so we asked around. This is a very old recipe and everyone assured us there was nothing to worry about (they laughed in fact). Nevertheless, before we sold any, we had those beads tested.
We gave a few grams of beads to a friend who works at an environmental testing lab. He tossed them on his desk and forgot about them for almost a week. It was just a bunch of glass beads, after all. Imagine his surprise, when the sample fogged all the film badges of everyone around his desk.
Our 30 gram sample at the testing lab was putting out about 12 microRads/hr as measured right at the surface of the sample. This isn't very much. In fact, you'd get more than this just riding a jet aircraft from coast to coast. Low background radiation (what you get just walking around everyday) is about 2-10 microRads/hr depending on where you live. A chest x-ray exposes you to about 30 microRads.
Our radiation therapist friends tell us it's nothing to be worried about, and we agree. The hazard is very, very slight. But, what if someone made a whole necklace out of these beads and then wore it right next to their thyroid, several days a week for a year or so? You get the idea...why even provide an opportunity for hazard? So, we aren't selling any of the beads. It is however a really beautiful color. (sob!)
Here's how you can recognize (and avoid, if you're concerned) this kind of glass. Uranium glass has a very distinctive YELLOW-GREEN fluorescent color. It actually absorbs incident light and then re-radiates or fluoresces at its own characteristic wavelength, that YELLOW-GREEN color. Ordinary glass merely reflects the incident light. Chrome green glass is a darker and greener color, and doesn't look like it's glowing by its own light like the uranium glass does.
Here's how we show people the difference. Go into any antique shop. Look at just the green glass. You'll immediately notice that some of the glass is distinctly more YELLOW-GREEN than the rest and that it almost seems fluorescent. It is! That's uranium glass. At least here on the West Coast, every antique store we've been in has had about equal amounts of chrome green (harmless) glass objects and uranium glass (radioactive) objects.
There's a lot of the stuff around, so if you're interested it's pretty easy to spot the difference. Another really good test is simply to illuminate the glass with a "black light" or ultraviolet source. The uranium glass will glow distinctively. Some stores even specify that an object glows under "black light" and charge more.
Again, the hazard is pretty low, and most everyone seems unaware or at least unconcerned. Just don't buy that beautiful YELLOW-GREEN antique crystal decanter with 6 matching glasses to keep your liquor in. On the other hand, if you only drink about as much as we do, and the liquor just sits in the decanter for about a year of so, it might be just the thing for serving to those "special" friends, you know, like the ex-spouse, who's still behind on child support, or that obnoxious relative who still sneers because you're "just" doing bead work.