Way before its radioactive properties were discovered and exploited for both good (think nuclear power) and bad (think nuclear war), way before it officially was granted its place among the elements of the periodic table, the rare metal uranium was used by ancient Romans to color glass.
Back in 79 C.E. or so, radioactivity — or uranium — meant nothing to the Romans. To anyone. The concept, the reality, simply didn't exist. Neither did Uranus, the planet for which uranium is named, for that matter.
Yes, the Romans used uranium in their glass, and modern versions of the stuff still exists. It goes by a few different names and is even still being produced in some quantities in Europe. But it's more of a curio now than anything, found in the form of pitchers and bowls and other glassware in flea markets, dusty attics, museums and among glass collectors, all reminders that at one time it was something desirable.
"It is kind of attractive because it has that iridescent glow to it under certain lighting conditions. It really looks kind of special," says Paul Frame, a retired health physicist at Tennessee's Oak Ridge Associated Universities, a consortium of schools founded after World War II as the Oak Ridge Institute of Nuclear Studies. For years, Frame was also the curator at ORAU's Health Physics Historical Instrumentation Museum, also known as the Museum of Radiation and Radioactivity, which chronicles "the scientific and commercial history of radioactivity and radiation." The collection is located in Oak Ridge, Tennessee.
"There are many different types of collectors that would be interested in this sort of item," Frame says of the glass. "There are some people out there that are particularly interested in it because it's radioactive. And there are other people who just collect glassware; the styles and so forth.
But there's so much of this damn stuff out there that, despite the fact that there's a variety of people that are interested in it, it really doesn't have a lot of value unless it's a particularly unique piece of glassware ... size, design, artistry, that kind of thing."
In a word, yes: Uranium glass — Vaseline glass, sometimes called depression glass — is indeed radioactive.
That said, there's no need to run for the hills or the latest bomb shelter.
"It's absolutely true," Frame says. "What we're dealing with, with Vaseline glass, is something that is radioactive — just like everything else. And it is more radioactive than the majority of things, in that you can detect the radioactivity of Vaseline, or uranium glass, with a handheld meter [like a Geiger counter]."
"Marie Curie got these ore residues from the Czech Republic back in the day, and she extracted the uranium but discovered what was left behind was even more radioactive than the uranium itself. The material that made the residues most radioactive turned out to be radium, not the uranium," he says. "So in uranium ore, you have this whole host of radioactive stuff, and the key player there is really radium. Radium 226. The uranium itself is not all that radioactive."
Still, Frame will admit, there may be some small, infinitesimal risk involved with uranium glass, even though uranium is nowhere close to being as radioactive as, say, radium, another uranium byproduct.
"It's basically a theoretical risk. The radioactive exposures you get from flying in an airplane, or inhaling air in your home, which has radon in it, they're so much greater than any dose that anyone's going to get from uranium or Vaseline glass," Frame says. "There is, for all practical purposes, no risk. Zero risk."
Which, for collectors and admirers, is good news. Because glass that glows is just pretty cool.