Uranium glass is any glass that contains uranium oxide as a coloring agent, typically producing shades of yellow or green. The uranium content usually ranges from trace amounts up to about 2% by weight in modern pieces, though some antique items contain significantly more. What makes it famous is its vivid green fluorescence under ultraviolet (UV) light, a party trick that has turned it into one of the most collectible types of vintage glassware.
Why It Glows Under UV Light
The signature green glow comes from uranyl ions embedded in the glass matrix. When UV light hits the glass, those ions absorb the energy and re-emit it as visible green light, a process called fluorescence. The emission peaks in the green part of the spectrum, around 520 to 530 nanometers, which is why the glow looks so intensely neon-green in a dark room. This isn’t a faint shimmer. Under a good UV flashlight, a piece of uranium glass lights up like a highlighter.
Most uranium glass fluoresces brightly under a standard 395nm UV flashlight, the kind you can buy for under $15 online. A small number of pieces only respond well to shorter-wavelength 365nm UV light. If you’re testing glass you suspect contains uranium, try both wavelengths before ruling it out.
How to Tell It Apart From Other Glowing Glass
Uranium glass isn’t the only glassware that reacts to UV light, and the differences trip up a lot of collectors. Manganese, which was commonly used as a decolorizer in old glass, also fluoresces green under 365nm light and gets mistaken for uranium regularly. The key difference: manganese glass generally does not glow under 395nm UV, while nearly all uranium glass does. Testing with a 395nm light first is the fastest way to sort them out.
Selenium glass, found in pink, red, and ruby-colored pieces, can glow an intense pink under UV but is noticeably dimmer than uranium glass. Lead crystal fluoresces under shortwave 254nm UV light but not under the longwave lights most people use for uranium glass hunting. If your piece glows vivid green under a 395nm flashlight, you almost certainly have uranium glass.
Types and Terminology
The language around uranium glass can be confusing because collectors use several overlapping terms. “Vaseline glass” refers specifically to transparent or semi-transparent uranium glass with a yellow-green color resembling petroleum jelly. “Custard glass” is an opaque, creamy yellow variety that also contains uranium. Some green Depression-era glass contains uranium as well, though not all green Depression glass does. The umbrella term “uranium glass” covers all of them.
Colors range from pale yellow to deep emerald green, depending on the concentration of uranium oxide and other minerals in the recipe. Even some glass that doesn’t look green or yellow in daylight will reveal its uranium content under UV light.
A Brief History
Uranium has been used to color glass far longer than most people expect. A yellow glass mosaic containing about 1% uranium oxide was found in a Roman villa near Naples, Italy, dating to around 79 AD. Intentional, large-scale production began in the 1830s in Bohemia (modern Czech Republic), and uranium glass quickly became fashionable across Europe and the United States through the rest of the 19th century and into the early 20th.
Production stopped during World War II when governments seized uranium supplies for the Manhattan Project and nuclear weapons development. The pause lasted about 15 years. When production resumed around 1959, manufacturers switched from natural uranium to depleted uranium, a byproduct of nuclear fuel processing that has most of its more radioactive isotopes removed. Some artisan glassmakers still produce uranium glass today, though the most sought-after pieces among collectors date to the pre-war era.
Is It Radioactive?
Yes, uranium glass is mildly radioactive. The uranium in the glass emits low levels of alpha, beta, and gamma radiation. But “mildly” is the important word here. A uranium drinking glass at a distance of one foot produces roughly 9 microsieverts per hour of gamma radiation. At three feet, that drops to about 1 microsievert per hour. For context, the average person absorbs about 0.06 microsieverts per hour just from normal background radiation, so a uranium glass piece on a shelf across the room adds very little to your daily exposure.
The radiation drops off sharply with distance and is blocked easily by other materials. Displaying uranium glass in a cabinet poses negligible risk. Holding a piece occasionally, such as when examining it or showing it off, exposes you to a fraction of what you’d receive during a cross-country flight.
Is It Safe to Eat or Drink From?
This is the more practical concern, and it comes down to leaching. A study that tested 33 glass items found that the maximum amount of uranium that leached from uranium-bearing glass into liquid was about 30 micrograms per liter under realistic conditions. That’s a very small amount. For comparison, uranium-glazed ceramic items in the same study leached up to 300,000 micrograms per liter, roughly 10,000 times more. The glass matrix locks uranium in place far more effectively than a ceramic glaze does.
Most collectors treat uranium glass as display pieces rather than everyday dinnerware, which is a reasonable approach. Occasional use for serving food is unlikely to produce meaningful exposure, but regularly drinking acidic beverages (wine, citrus juice, vinegar-based dressings) from uranium glass could increase leaching over time. Chipped or damaged pieces expose more surface area and should be kept out of food contact.
Legal Status and Regulations
Uranium glass is completely legal to buy, sell, own, and collect in the United States. The Nuclear Regulatory Commission specifically exempts glassware containing up to 2% uranium by weight from licensing requirements. For glassware manufactured before August 27, 2013, that threshold is even higher at 10% by weight, covering virtually all antique pieces. You don’t need any permit or special handling to purchase uranium glass at an antique store, estate sale, or online.
The one restriction worth noting: manufacturing new uranium glass products for sale requires a license under NRC rules. The exemption covers possession and transfer of finished products, not production. This is why new uranium glass comes from a relatively small number of licensed artisans rather than mass-market manufacturers.
How Collectors Find It
The most reliable method is carrying a small UV flashlight to antique shops, flea markets, and estate sales. A compact 395nm flashlight fits on a keychain and instantly reveals uranium content in any glass you test. Thrift stores and secondhand shops are popular hunting grounds because uranium glass often gets mixed in with ordinary glassware and priced accordingly.
Common finds include Depression-era serving dishes, candy dishes, vases, juice glasses, and decorative figurines. Bohemian and American pieces from the 1880s through 1930s are especially prized. Prices range from a few dollars for small, common items to several hundred for rare patterns or large pieces in perfect condition. The combination of radioactivity, history, and that unmistakable glow has made uranium glass one of the more active niches in the antique glass collecting world.