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PSA: Uranium Glass

Uranium glass under ultraviolet light, by Realfintogive, CC BY-SA 3.0 via Wikimedia Commons

Apparently collecting uranium glass is currently A Thing. In a discussion on Bluesky last week, someone offered up this Washington Post article from a year ago. It’s got some problems.

Uranium glass and older orange Fiestaware use uranium as a colorant. The glass fluoresces under ultraviolet light. They’re safe to keep in your china cabinet, as I do, but less so for eating from. The danger is not their radioactivity, but rather uranium’s properties as a heavy metal that will damage kidneys and other organs. Oh, and the fluorescence has nothing to do with uranium’s radioactivity.

The Washington Post article is a trove of misinformation from a person who clearly does not understand what she is writing about. It’s bad enough that I’m going to deconstruct it in detail.

The very first paragraph tells us to prepare for errors.

While roaming my favorite antique store outside Atlanta recently, I heard a “click click” sound and turned around to see a woman shining a black-light flashlight on a green plate. A few minutes later, a man joined her with a black box that began to hum when it got close to the plate. It was the unmistakable sound of a Geiger counter, a tool used to detect radioactivity. Like me, they were in search of a specific kind of vintage treasure: the green glow of uranium glass.

Generally, one would expect the black-light source to hum and the counter to click-click. There are some types of counter that hum, but I can’t think of a black-light source that clicks, except when you turn it on and off.

She gives a history of uranium glass and how it’s made that seems okay. I’m concerned about the safety aspects.

The style of glass waned in popularity during World War II and the postwar era, when uranium was highly regulated, because it was needed for the war effort. In 1958, though, it was deregulated. When they began producing the glass again, the uranium was depleted, meaning its radioactivity was significantly lower than natural uranium. [emphasis mine]

Depleted uranium is uranium from which most of the 235 isotope, the one useful in nuclear weapons, has been removed. It is slightly lower in radioactivity than natural uranium, but that is largely irrelevant. Natural uranium isn’t strongly radioactive.

Some items do emit small amounts of radiation, according to the Environmental Protection Agency. The level of radioactivity varies by piece, ranging from less than 1 percent to up to 25 percent by weight, but there is no recognized danger to handling or using uranium glass, according to the U.S. Nuclear Regulatory Commission

“The level of radioactivity” is not measured in percentage, so I clicked the two links in that sentence. From a publication called Collection Weekly, they appear to be major sources for the Washington Post article. “The level of radioactivity” is what the linked articles give as the weight percent of uranium in the glass.

Let’s start with the improbable: 25 weight percent uranium. Glass mixtures can vary over some wide ranges. Uranium oxide can melt into the standard glass mixtures, although it seems to me that 25% could be difficult to work with. Additionally, it’s a lot of the expensive component of the glass, where much less would provide color. It definitely will be a health risk, although NOT because of the radioactivity. There is some additional dithering that can be done around whether this is weight percent of uranium or of uranium oxide, but uranium is heavy enough to let that pass.

Uranium glass should not be used for food. The danger, as with lead glass, is that the heavy metal will leach into the food and damage kidneys and other internal organs. Acidic food particularly can leach the metals. Given the level of ignorance around this subject, I’m going to assume that the people asking these questions don’t know what an acidic food is. So just don’t use uranium glass for food. Decoration only.

This quote from a health physicist considers only the radioactivity and is correct as far as that goes, which isn’t far enough.

Eating off uranium glass poses minimal risks, according to Paul W. Frame, a senior health physicist at Oak Ridge Associated Universities, and no special treatment is required when disposing of it.

“You’re dealing with chemically purified uranium [in uranium glass],” Frame says. “Uranium that has been chemically purified is generally not that much of a risk. It’s not particularly radioactive.” 

And he gets the radioactivity part wrong. Radioactivity is a property of atoms. Uranium is radioactive, but it has a long half-life, which means that its atoms break up over a long period of time and thus present little radioactivity. He may be using “chemically purified” to mean “U-238 from the enrichment process,” but that goes back to the tiny difference between natural uranium and depleted uranium. Oak Ridge, where are you getting your health physicists?.

A health physicist should have said something about heavy metal poisoning. Maybe he did, and the writer decided to leave it out.

While reading the articles, I stumbled on something that wouldn’t have occurred to me: the idea that uranium compounds’ fluorescence has something to do with their radioactivity. It doesn’t. The uranium atoms absorb the higher-energy ultraviolet light and then emit it at lower wavelengths of visible light. Zinc sulfide and a number of other compounds that enliven the stars one can stick on the ceiling of a child’s bedroom do something similar, and they’re not radioactive. It’s a totally different process.

All of the editors involved in getting this article to print should be ashamed of themselves.

Cross-posted to Nuclear Diner

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