The leading company was Northwood but custard was also made by Heisey, Tarentum, Dithridge, U.S. Glass… American colorless pressed glass made before 1930 is said to fluoresce yellow, while reproductions generally do not.. 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. Old Burmese glass fluoresces a similar yellow-green color. Due to the presence of uranium oxide in the glass, the glass will glow a bright green color when put under a black light- this is the best way to identify it. 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. Pamela Wiggins. I have avoided the term "Vaseline Glass" because there are conflicting interpretations of what it means. Above: Two green uranium glass vases by Sowerby of Gateshead, made in the 1930's. Watch for glass that is yellow-green in appearance and looks slightly iridescent. Uranium, fluorescent and Vaseline Glass. The vases rest on a Vaseline glass base. In this article Fluorescent Glass and Uranium Glass are defined very simply as any kind of glass which has uranium in it. 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. 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. Both green Depression glass and Vaseline glass will glow under a black light due to the uranium oxide content in the glass. Also, we like to oooh and aaah over glowy glass! 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. The fluorescence of vaseline (uranium) glass is always green. This is Vaseline glass and is made by adding 2 percent uranium dioxide to the glass ingredients. Back to Glass Encyclopedia Home. 1930-1950s. This is called Burmese glass, because its color reminds the sunset of Burma country. While uranium is radioactive, it isn’t actually bad to drink or enjoy food in the glassware that uses this. Mary Gregory Glass Identification Guide + Gallery. 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. 1895-1910 then again as kitchen glassware, ca. Above: Flower vases made at the Thomas Webb & Sons factory in England. Uranium glass is a type of glass that has uranium, usually in the form of oxide diuranate, added to the mixture before melting. Custard glass is a creamy pale yellow opaque glass (mostly pressed) made primarily in America, ca. 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