Even if it seems hard to believe, in the not too distant past there were people who were exposed to high levels of radiation to make uranium glass, a fluorescent glass that shines in shades of green when exposed to ultraviolet light.
Although the production of this material was stopped after the Second World War, some collectors of antiques still keep uranium glass objects in their homes.
As the name suggests, uranium glass is a special glass made of uranium oxide, which gives it a yellow or yellow-green hue when exposed to ultraviolet rays but also makes it radioactive.
The concentration of uranium in this type of glass is usually around 2%, although in porcelain manufactured in the early twentieth century the concentration was up to 25%.
Interestingly, the fluorescence of glass is not related to the radioactivity of uranium. The higher the concentration of uranium in the glass, the lower the fluorescence. For this reason, objects with a uranium oxide content of more than 25% completely lose their lustre. Uranium glass is generally considered safe, but with one condition: not to be used constantly.
Glasses and other objects made of this material can occasionally be touched, but keeping food and drink (especially acidic ones) in these containers are dangerous because they tend to release uranium.
Collectors are also advised not to spend more than two hours a day manoeuvring uranium glass objects to avoid radiation.
This stuff is not a recent invention, as one might think. A mosaic discovered in a Roman villa in Naples, Italy, which contained pieces of uranium glass with a uranium concentration of 1%, proves that this material has been used since ancient times.
Counting collector's trends, Uranium glass value is rising.
But no matter how popular uranium glass was, the danger it posed primarily to those working in production could not be ignored for long. Repeated contact with uranium oxides has caused serious health problems for workers.
At the beginning of World War I, as knowledge about the danger posed by uranium spread, this substance became heavily regulated, and after World War II the production of uranium glass was gradually stopped.