Uranium glaze
A uranium glaze is a colored, uranium-containing glaze for ceramics . It was mainly used in the USA in the first half of the 20th century, but also in Germany and Austria, but has only played a subordinate role since then.
description
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Initially, pitchblende , sodium diuranate and uranium (V, VI) oxide , later also uranium (VI) fluoride, were used to produce the glazes . Depending on the chemical composition of the raw materials, the addition of other substances and the firing temperature, the color of the glaze ranges from lemon yellow and orange through red and green to brown and black. The green, brown and black shades are created under neutral or reducing firing conditions or by adding oxides of the elements cobalt , chromium , iron or manganese . The yellow, orange and red tones are created by oxidative firing conditions or by adding uranium to lead glazes . Cer (IV) oxide or cobalt (II, III) oxide as additives form a blue or transparent green color.
history
Uranium was used for the manufacture of ceramic glazes shortly after its discovery by Martin Heinrich Klaproth in 1789, but it wasn't until Adolf Patera improved the manufacturing process in the middle of the 19th century that it was rapidly spreading. Between 1900 and 1943, ceramics containing uranium were produced in large quantities in the USA , but also in Germany and Austria, which was also due to the fact that the yellow cake used as a raw material was very cheap. The low price was due to the fact that yellowcake was a waste product from the extraction of radium and vanadium . It is estimated that between 1924 and 1943, 50–150 tons of uranium (V, VI) oxide were used annually in the USA to make glazes containing uranium. In 1943 the US government imposed a ban on the civil use of substances containing uranium, which lasted until 1958.
From 1958 the US government, and from 1969 also the United States Atomic Energy Commission, sold depleted uranium in the form of uranium (VI) fluoride for civil use. In the 1950s and 1960s, uranium glaze mainly adorned tableware in the USA. A large producer of such dinnerware at that time was the Homer Laughlin China Company , which sold it under the brand name Fiesta . In Germany, ceramics were manufactured by the porcelain manufacturer Rosenthal , among others , and were available in stores until the early 1980s. Uranium was also used to glaze tiles. However, since alternative dyes for glazes were developed during the ban, some of which were cheaper and easier to obtain, uranium now only plays a very subordinate role as a starting material for glazes, including in the arts. Older ceramic objects with uranium glazes are valued by collectors and are often offered for sale at flea markets.
Health risk
Objects covered with glazes containing uranium show measurable alpha , beta and gamma radiation , which, however, is below the limit values and is therefore classified as too low to represent a health risk. Can on the surface of gamma rays - dose rates of up to 2000 nSv occur h /. Radon ( 222 Rn) formed by radioactive decay in the uranium-radium series is so firmly bound in the glaze that it cannot escape. If eating utensils come into contact with acidic foods such as fruits or vinegar, but also through mechanical abrasion, uranium compounds can loosen from the glaze and enter the body through food. It is therefore recommended that ceramics with uranium glaze only be used as collector's items and not for everyday use.
See also
literature
- Henning Philips Born, Rudolf Geipel: Uranium colors uranium glasses, uranium glazes, radiometric, technical, historical (= Series of the mining and industrial museum Eastern Bavaria . No. 46 ). Mining and Industry Museum East Bavaria, Kümmersbruck / Theuren 2005, ISBN 3-925690-55-7 .
- Rudolf Geipel, Henning von Philipsborn: Natural radionuclides in everyday objects using the example of uranium glasses and uranium glazes . In: Radiation Protection Practice . tape 1 , 2001, ISSN 0947-434X .
Web links
Individual evidence
- ↑ a b c d e Robert Josef Schwankner , Michael Eigenstetter, Rudolf Laubinger, Michael Schmidt: Radiant treasures: Uranium as a color body in glasses and glazes . In: Physics in Our Time . tape 36 , no. 4 . Wiley-VCH Verlag, 2005, ISSN 0031-9252 , p. 160-167 , doi : 10.1002 / piuz.200501073 .
- ↑ a b Angelika Sauerer: Radiant phenomena. In: www.mittelbayerische.de. Retrieved July 18, 2016 .
- ^ Daniel Rhodes: Clay and Glazes for the Potter . Martino Fine Books, 2015, ISBN 978-1-61427-799-6 .
- ↑ a b c National Academy of Science - National Academy of Engineering (Ed.): Trends in the Use of Depleted Uranium . Report of The Ad Hoc Panel on Depleted Uranium. Washington June 1971, p. 40-42 .
- ↑ a b Alan Boyle: Uranium hunter follows trail of tiles. In: www.nbcnews.com. Retrieved June 27, 2016 .