Uranium marbles (27/09/09)
Anyone who plays around with lasers and fluorescent materials simply has to have a set of uranium marbles! Nothing quite matches the wonderful green fluorescence they emit when excited with UV light.
Uranium glass (see the Wikipedia article) contains around 2% of uranium oxide and therefore emits a strong green fluorescence. It was quite widely used for tableware in the early 20th century, but the only way you can get it now is second hand. EBay has a wide selection of plates, dishes, cups, saucers and whatnot, and also the obligatory marbles. The set shown below cost around £8 and came with a free invisible-ink pen with a UV LED on the end, which was rather neat. Since the glass contains uranium, it is obviously slightly radioactive, but the levels are so low as to be insignificant.
