If you're a serious collector of pottery or glass, you probably own a UV (ultra violet) tube, popularly called a "black light." This useful tool not only reveals hidden flaws and repairs, but it can also activate the tell-tale neon-green fluorescence that indicates the presence of uranium.
The use of uranium in glass was much more prevalent than most people realize. Not long after the discovery of uranium in 1789, glassmakers began experimenting with uranium compounds as colorants, and in the period between the 1830's and World War II, all manner of objects made of the glass - from everyday drinking glasses, cups, and dishes to decorative pieces and art glass - appeared on the market.
During the war, supplies of uranium were diverted to the development of the nuclear bomb. By the time the commercial production of uranium glass resumed in 1959, government restrictions and the negative connotations associated with radiation forced manufacturers to switch to depleted uranium, which is less radioactive. The relatively small quantities of uranium glass still being made today are of the decorative variety, such as the Burmese glass line made by Fenton Art Glass (USA).
But there is actually little to fear from pre-war pieces. With the exception of a few early 20th century specimens that were composed of up to 25% uranium by weight, the rest had around just 2% each and normally emit little radiation above what one would normally be exposed to naturally from the environment. The risks from exposure only increase if acidic liquids or foods are allowed to stay in contact with the glass, leeching minerals in the food, or if the glass is sanded or abraded, releasing particles into the air which could be inhaled.
Not all uranium glass looks alike. Vaseline glass - so named because it resembled the ointment at that time - was so popular between the 1880's and the 1920's that the term is sometimes used as a synonym for uranium glass. Purists define Vaseline glass as a transparent yellow/yellow-green glass that derives its color from its 2% uranium oxide content. It's identified by fluorescence, or as VGCI (Vaseline Glass Collectors, Inc.) members like to say, "If it doesn't turn green, it's not Vaseline!"
Other well-known versions of uranium glass include some Depression and Carnival. Many green Depression glass pieces, in particular, are considered less-valuable versions of Vaseline glass because lead has been added to deepen the color.
Burmese glass dates to the 1880's and is distinctive for the gradual shift from a canary-yellow bottom to a salmon-colored top. This is achieved, in part, through the addition of soda ash, lime, and gold. (Burmese is so-named because Queen Victoria, when presented with a gift of the glass, remarked that the colors reminded her of a Burmese sunset.)
Jade glass, also known as Jadite or Jadeite, is another particularly popular type of uranium glass. It was marketed by such companies as McKee and Jeannette Glass in the 1920's and '30's, but by the time Anchor-Hocking's Fire-King Jade-ite line appeared in 1942, uranium was no longer being added.
Prices for uranium glass vary widely depending upon rarity and condition, but most fall within the $10 to $300 range, so creating a collection is an affordable endeavor, especially if you recognize pieces at yard and estate sales that everyone else has overlooked. If you suspect a piece might be, for example, Vaseline, and you don't have your portable black light or Geiger counter with you, hold it up to bright sunlight. If it's genuine, the glass should take on a subtle greenish glow as the uranium fluoresces under the sun's ultraviolet rays.
Would you like to discover more about this popular collectible? Check out the resources listed below, and
The Big Book of Vaseline Glass, by Barrie W. Skelcher
Fenton Burmese Glass, by Debbie Coe
Pictorial Guide to Vaseline Glass, by Sue C. Davis
The Picture Book of Vaseline Glass, 2nd Revised and Expanded Edition, by Sue C. Davis and Bill McFarling
Vaseline Glass: Canary to Contemporary - The Comprehensive Guide to Yellow-Green Pattern Glass, Art Glass and Novelties from 1840 to the Present, by David A. Peterson
Vaseline Glassware: Fascinating Fluorescent Beauty, by Barrie W. Skelcher
1st Glass - British site's informative section on vaseline/uranium glass includes a large photo gallery.
The History of Burmese Glass - Explains how Burmese glass is made, with a focus on Fenton.
Radioactive Glassware in Your House? Could be! - Videos by Tom of Anti-Proton.com demonstrate use of Geiger counter and black light.
Uranium Glass Great article by Barrie Skelcher with an emphasis on uranium measurements.
Vaseline Glass Collectors, Inc. (VGCI) - Major site devoted to Vaseline glass includes definitions, Glass Manufacturers Gallery, UV Blacklight Fun Page, more. Organization also sponsors an annual convention.
Vaseline and Uranium Glass (ca. 1930s) - Authoritative article from Oak Ridge Associated Universities includes detailed assessment of radiation exposures.