When hunting for treasures at estate sales, a black light can be incredibly useful to have. Yup, the ultraviolet light you had in your college dorm is good for more than just illuminating your Grateful Dead poster and reminding you about the mustard stain that didn’t come out in the wash. It can also help you identify different glassware. Most notably, it can help you identify glass containing uranium.
This sounds much scarier than it is, and precisely as cool. Uranium glass is a popular collectors’ item, and with good reason. This magical glass can come in a variety of shapes and forms—from dinnerware to decorative vases. It is black light reactant, glowing a bright green when near the proper lighting. And while it does emit low-level radiation, it’s generally believed that it’s not enough to cause bodily harm, or to turn you into an X-Man. With the exception of some early 20th century pieces, most uranium glass contains no more than 2% uranium oxide—often much less. That’s certainly not enough to get Jean Grey powers—heck, that's not even enough for Dazzler.
It’s understandable why uranium glass would capture curiosity of collectors. Its backstory makes it a great conversation piece, and there's enough variety—plain or painted, hobnail or smooth—that anyone interested can find something to suit their tastes.
So let’s talk a bit about some of the different types of uranium glass.
Originally called “canary glass,” these pressed glass pieces quickly took on the name “Vaseline” because its yellow hue was reminiscent of the medicine cabinet staple (and let’s face it, “petroleum jelly glass” just doesn’t have quite the same ring.)
Vaseline / canary glass refers specifically to the transparent yellow or yellow-green glass that glows bright green under black light. It’s not uncommon for any green depression glass to be misidentified as Vaseline—the uninitiated vendor may not know there’s a difference. Or they might see Vaseline as a hotter seller than yellow or green depression glass.
And Chris Cope, a Vaseline glass collector and a board member for Vaseline Glass Collectors, Inc. says it’s not uncommon for new collectors to misidentify the glass. “Normally, if they find anything that’s green and glows, they say it’s Vaseline glass.”
But secrets come out in the black light. The truth, like the Green Lantern’s ring, glows green with righteousness. Without uranium content, the glass won’t fluoresce.
Vaseline glass tchotchkes are a plentiful lot, having been manufactured since the early 1800s, with a brief haitus around World War II when uranium supplies were limited. And it’s still being made today, most often in the form of beads and marbles, and less so in the form of art glass.
“That’s what I think is most unique about Vaseline glass—it’s really one of the only glasses I know of that crosses nearly every single area of glass. It goes back as far as the 1840s, all the way to modern times, almost every major country and every major glass manufacturer used Vaseline glass at some point. And I don’t think any other glass that people collect, really, have that feature—crossing decades and every manufacturer,” Cope said.
Custard glass was originally marketed by Sowerby as “Queen’s Ivory Ware,” but just like Vaseline glass, it was given its more colloquial name based on it’s appearance—smooth, opaque pressed glass in creamy yellow hues, just like the puddingy dessert.
And just like Vaseline glass, it contains uranium, and will glow green under black light. But if you’re looking for early-era custard glass, the best way to confirm that you’re not falling prey to a reproduction is to look for the “ring of fire” that comes along with the vintage glass. Hold the glassware up to the light, and look for a red ring around the rim of the glass, just like you would for milk glass. Modern custard glass lacks the opalescence, and therefore, the ring.
Yet another style of opaque uranium glass, this art glass transitions from yellow to pink (or vice versa). The yellow, as you would expect, is due to the uranium oxide, but the pink hue is from the addition of gold tincture. Once the glass is blown, re-heating (aka striking) specific areas of the glass will change its color.
So although much of any piece of Burmese glass is pink, the entire piece contains uranium, including the pink part, which was created through by adding gold and higher temperatures to the glass.
Reproductions can be spotted by holding the glass to the light—modern Burmese glass often has swirls and streaks within the glass. Original Burmese art glass is unlikely to have such internal perfections.
Burmese glass isn’t the only uranium glass to feature colors beyond yellow and green. It’s all in the additional additives the glassmakers used. “There’s a red art glass called rubina verde,” Cope said, as well as pieces of blue and Vaseline and orange and Vaseline. All will glow green from the uranium. “But the hardest to find,” Cope said, “is purple and Vaseline.”
So what to do with this fabulous glass once you’ve started collecting? The display possibilities are limitless. With the right lighting, a single vase can be a striking conversation piece, or you can let multiple pieces light up a whole room. And, of course, if you have the dishware, you can allow them to serve a more practical purpose—dinner parties! “I did go so far as to put together a complete table setting and was going to have a party, I just haven’t done it yet,” Cope said. “It’s a good idea,” he said, “I just haven’t followed through.”
There are those that still believe Vaseline glass is unsafe for food uses. Others are comfortable using them, but avoid using them with acidic foods, which could potentially leach chemicals from the dishes. Others are unconcerned. “There’s no safety concerns. They’ve done extensive tests, the glass is completely safe,” Cope said. “There’s also speculation if the glass breaks, uranium would be released. It won’t. It’s not a capsule. It’s still in the glass.”
But regardless of whether you dare to dine off the dishes, or simply surround yourself with chartreuse tchotchkes, deigning to set them aglow only on special occasions, you’ll find a variety of uranium glass at estate sales.