Vaseline glass is a type of transparent yellow to yellow-green glass that contains uranium oxide as its coloring agent. The name comes from its resemblance to petroleum jelly: held up to normal light, it has that same greasy, translucent yellow-green look. What makes it famous, though, is what happens under ultraviolet light. Hit it with a black light and it fluoresces a vivid, almost electric green.
Why It Glows Under Black Light
The glow comes from the uranium oxide mixed into the glass during manufacturing. When UV light at around 365 nanometers strikes the glass, the uranium atoms absorb that energy and re-emit it as visible green light. This fluorescence is the single most reliable way to identify a genuine piece. Under normal lighting, vaseline glass can look pale green or yellowish and be easy to confuse with other vintage glassware. Under a black light, there’s no mistaking it.
The uranium content in most vaseline glass runs about 2% by weight, though some pieces from the early 1900s contained as much as 25%. A longer UV wavelength won’t trigger the fluorescence, so collectors typically use a 365 nm black light for testing.
How It Was Made
Glassmakers added uranium oxide directly to the molten glass mixture, where it served as both a coloring agent and a source of that signature fluorescence. Uranium oxide was first used this way in the 1830s, and the technique spread across Europe through the 1840s. By experimenting with different additives alongside uranium, manufacturers could produce a range of colors, not just the classic yellow-green.
During the Great Depression, some makers added iron oxide to intensify the green glow. Collecting purists consider these pieces a separate category from “true” vaseline glass, which should be transparent and yellow-green without the iron boost.
A Brief History of Production
Vaseline glass hit its peak popularity between the 1880s and 1920s, when manufacturers like Fenton, Cambridge, Northwood, and Boyd produced large quantities in a range of patterns. Geometric shapes, hobnail textures, and intricate floral designs were especially common during this era.
Production came to an abrupt halt in the United States during World War II, when the government confiscated civilian uranium supplies for the Manhattan Project. A few companies resumed making it after the war, but on a much smaller scale. Today, very little vaseline glass is produced because of tighter government restrictions on uranium dioxide. That wartime gap in production is a big reason pre-1940s pieces are so sought after by collectors.
Vaseline Glass vs. Uranium Glass
The terms “vaseline glass” and “uranium glass” are often used interchangeably, but collectors draw a distinction. Uranium glass is the broader category: any glass colored with uranium oxide, regardless of its final appearance. Vaseline glass is a specific subset, referring only to the transparent yellow to yellow-green variety that looks like petroleum jelly under normal light. A piece of red or opaque green glass could still contain uranium and fluoresce under UV, but it wouldn’t be called vaseline glass.
Custard glass, another related category, is opaque and creamy yellow. It sometimes contains uranium and will glow under a black light, but its opacity and color set it apart from vaseline glass visually.
Is It Safe to Handle and Display?
Vaseline glass is mildly radioactive. Gamma and beta radiation measured at 1 centimeter from the surface of uranium-glazed items ranges between about 3.1 and 9.2 milliroentgens per hour. That sounds alarming, but the exposure drops off sharply with distance. Sitting on a shelf across the room, a piece of vaseline glass contributes a negligible amount of radiation to your daily life, well within the range of normal background exposure.
The U.S. Nuclear Regulatory Commission exempts glassware containing up to 10% uranium by weight from licensing requirements, which covers the vast majority of vaseline glass on the market. Owning, displaying, and handling it is perfectly legal and considered safe for casual use.
Using It for Food and Drink
This is where a bit more caution is warranted. A 1992 study that leached uranium glass sequentially with water, dilute acetic acid, and stronger acid solutions found that uranium-bearing glass released up to about 30 micrograms per liter of uranium into liquid. That’s a relatively small amount, especially compared to uranium-glazed ceramics, which leached up to 300,000 micrograms per liter in the same study. Still, most collectors treat vaseline glass as decorative rather than functional. If you want to admire it on a shelf, there’s essentially no risk. Using it daily for acidic drinks like orange juice or wine is a different conversation.
What Collectors Look For
Vaseline glass spans a wide price range. Simple, common pieces sell for $10 to $50, while rare items from well-known manufacturers can reach several hundred or even thousands of dollars. The factors that drive value are similar to other antique glass: age, maker, condition, pattern, and scarcity.
Flipping a piece over to check for a maker’s mark on the bottom is the first step. Logos from Fenton, Boyd, Cambridge, or Northwood carry extra weight with collectors. Pre-war pieces (made before the 1940s uranium confiscation) are generally more desirable because that production gap made them scarcer. Beyond the maker, look for the complexity of the pattern, the intensity of the fluorescence under UV light, and whether the piece has any chips, cracks, or repairs. A pristine hobnail bowl from a known manufacturer will always outprice an unmarked, chipped tumbler.
For anyone just starting out, a cheap 365 nm black light is the single most useful tool. It lets you quickly confirm whether a piece at a flea market or estate sale actually contains uranium, or whether it’s just regular yellow-green glass hoping to ride the vaseline glass hype.