Uranium glass

The normal colour of uranium glass ranges from yellow to green depending on the oxidation state and concentration of the metal ions, although this may be altered by the addition of other elements as glass colorants. Uranium glass also fluoresces bright green under ultraviolet light. File:Uranium glass beads, black background.jpg|Modern uranium glass beads File:Uranium glass beads, UV light.jpg|The same items under UV light Vaseline glass The most common color of uranium glass is pale yellowish-green, which in the 1930s led to the nickname "Vaseline glass", based on a perceived resemblance to the appearance of Vaseline-brand petroleum jelly as formulated at that time. Specialized collectors still define Vaseline glass as transparent or semi-transparent uranium glass in this specific color. Vaseline glass is sometimes used as a synonym for any uranium glass, especially in the United States, but this usage is frowned upon, since Vaseline-brand petroleum jelly was only yellow, not other colors. The term is sometimes applied to other types of glass based on certain aspects of their superficial appearance in normal light, regardless of actual uranium content which requires a blacklight test to verify the characteristic green fluorescence. In the United Kingdom and Australia, the term Vaseline glass can be used to refer to any type of translucent glass. Other colors Several other common subtypes of uranium glass have their own nicknames: • Custard glass (opaque or semiopaque pale yellow) • Jadite glass (opaque or semi-opaque pale green; initially, the name was trademarked as "Jadite", although this is sometimes over-corrected in modern usage to "jadeite") • Depression glass (transparent or semitransparent pale green). • Burmese glass (opaque glass that shades from pink to yellow) Like "Vaseline", the terms "custard" and "jad(e)ite" are often applied on the basis of superficial appearance rather than uranium content. Conversely, "Depression glass" is a general description for any piece of glassware manufactured during the Great Depression regardless of appearance or formula. ==Usage==

Ancient usage The use of uranium glass dates back to at least 79 AD, the date of a mosaic containing yellow glass with 1% uranium oxide, which was found in a Roman villa on Cape Posillipo in the Bay of Naples, Italy, in 1912. Medieval usage Starting in the late Middle Ages, pitchblende was extracted from the Habsburg silver mines in Joachimsthal, Bohemia (now Jáchymov in the Czech Republic), and was used as a coloring agent in the local glassmaking industry. By the 1840s, many other European glassworks began to produce uranium glass items and developed new varieties of uranium glass. The Baccarat glassworks in France created an opaque green uranium glass which they named chrysoprase from its similarity to the green form of chalcedony of the same name. File:Fluorescent Uranium Depression Glass.jpg|Fluorescent uranium Depression glass Image:U glass above.jpg|A uranium glass cakeplate glowing under UV light. Image:U glass with black light.jpg|Uranium glass glowing under UV light File:Uranium-glass-necklace.jpg|Uranium glass necklace, circa 1930. At the end of the 19th century, glassmakers discovered that uranium glass with certain mineral additions could be tempered at high temperatures, inducing varying degrees of micro-crystallization. This produced a range of increasingly opaque glasses from the traditional transparent yellow or yellow-green to an opaque white. During the Depression years, more iron oxide was added to the mixture to match popular preferences for a greener glass. This material, technically a glass-ceramic, acquired the name "vaseline glass" because of its supposedly similar appearance to petroleum jelly. , a few manufacturers continue the vaseline glass tradition: Fenton Glass, Mosser Glass, Gibson Glass and Jack Loranger. U.S. production of uranium glasses ceased in the middle years of World War II because of the government's confiscation of uranium supplies for the Manhattan Project from 1942 to 1958. After the restrictions in the United States were eased, several firms resumed production of uranium glass, including Fenton and Mosser; though uranium was still regulated as a strategic material. Following the Cold War, restrictions on uranium glass were completely lifted. During this time many older pieces entered the free market and new pieces continued to be produced in small quantities into the 2000s. Riihimäki Glass produced uranium glass designer pieces after World War II. Uranium glass is used as one of several intermediate glasses in what is known to scientific glass blowers as a 'graded seal'. This is typically used in glass-to-metal seals such as tungsten and molybdenum or nickel based alloys such as Kovar, as an intermediary glass between the metal sealing glass and lower expansion borosilicate glass. == Health concerns ==

Uranium glass can register above background radiation on a sufficiently sensitive Geiger counter, although most pieces of uranium glass are considered to be harmless and only negligibly radioactive. ==See also==