Vaseline glass can be identified by shining a black light, or ultraviolet light, on the glass, which will glow florescent green. This process adds colour to the glass. Pamela Wiggins. The rise of pressed glass made it possible to mass-produce glassware, leading to the creation of some of the most recognizable styles including carnival glass, elegant glass, milk glass, crystal glass, and Depression glass. Photo via Dave Peterson at VaselineGlass.org Top: The relationship between a piece of glass’s propensity to glow and its uranium content is often not predictable. The term 'Mary Gregory' indicates a style of glass rather than a manufacturer.It originates from the myth that a lady in USA named Mary Gregory painted scenes of children on thousands of items of glassware. Vaseline glass is a type of Uranium glass – glass with trace amounts of uranium added to color the glass. 1930-1950s. Mary Gregory Glass Identification Guide + Gallery. Above: Flower vases made at the Thomas Webb & Sons factory in England. This is Vaseline glass and is made by adding 2 percent uranium dioxide to the glass ingredients. Either red/orange fluorescence or blue/greenish-blue fluorescence means NOT vaseline glass.. 6) Opaque pink uranium glass (Burmese glass) Left hand cat looks pink with slightly green under sun light. The leading company was Northwood but custard was also made by Heisey, Tarentum, Dithridge, U.S. Glass… Usually, the trace levels of uranium are at around 2%, but in some glass pieces from the 20th century, up to 25% of the material is made up of uranium. I have avoided the term "Vaseline Glass" because there are conflicting interpretations of what it means. Old Burmese glass fluoresces a similar yellow-green color. Uranium glass is a type of glass that has uranium, usually in the form of oxide diuranate, added to the mixture before melting. Also, we like to oooh and aaah over glowy glass! The piece at left contains no uranium at all, while the dark piece at bottom-center contains the most of the group. Both green Depression glass and Vaseline glass will glow under a black light due to the uranium oxide content in the glass. While uranium is radioactive, it isn’t actually bad to drink or enjoy food in the glassware that uses this. The fluorescence of vaseline (uranium) glass is always green. Watch for glass that is yellow-green in appearance and looks slightly iridescent. Confusing Custard Glass. This is called Burmese glass, because its color reminds the sunset of Burma country. This practice dates back to the early 1800’s, and reached its height of popularity from the mid to late 1800’s up until the beginning of World War II. The vases rest on a Vaseline glass base. A community developed to share information on uranium glass - what it is and what it looks like, as well as how to hunt it, identify it, photograph it, and display it. Back to Glass Encyclopedia Home. 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