Early x ray tubes, including many in my own collection, when powered the electrons bombarding the glass would cause them to fluoresce a bright lime green during operation. Even after these tubes were turned off, they would continue to phosphoresce green for up to an hour or more.

Becquerel, the discoverer of radioactivity, believed the emission of x-rays from these tubes was a direct result of this green fluorescence, as the early x ray tubes had no metal target for the x-rays to emanate from, but were emitted directly from the glowing green glass.

Deciding that x-ray radiation was a phenomena of fluorescence, Becquerel started analyzing other known fluorescing compounds known at the time. Of these, uranium salts which fluoresced green were among the first he tried and on leaving them on a covered photographic plate, he found upon development, that the plate was fogged from radiation emitted by the uranium sample.

Also, as mentioned earlier, the early fluoroscopic x ray viewers would glow green upon exposure to x Ray radiation or any other kind of radiation including that from radioactive compounds. Indeed it was once wasses at the turn of the century where by looking through a lens, one could see the green scintillations, or flashes of light, as individual radioactive particles from a small sample of radium struck the zinc sulfide screen contained within.

I believe this all added to the color green as being forever identified with radioactivity. Even today at my local movie theater I’m reminded of radioactive green whenever I look at the glowing green exit signs, each filled with 5-10 curies (equivalent to 5-10 grams of radium) worth of a radioactive hydrogen isotope to cause the inner fluorescent coating of the glass tubes to light up, exactly as they would under high voltage electricity as a normal fluorescent light would, except these will run power-free for 20 years.

        cnocspeireag said:

My Dad passed on a WWII watch to me as a very young kid in the 1950s. It was so luminous that I could use it to read by late at night after ‘lights out’. That produced a green light. As it was behind a steel and glass case I suppose no alpha escaped. I don’t know what happened to it but I expect nowadays it should have been classified as radioactive waste.

Yeah, those were cool. Even if you knew where it was, it almost surely does not glow anymore. The radium is still plenty good, because it has a long halflife, but the florescent compounds in the paint degrade.

http://www.google.com/imgres?imgurl=http://z.about.com/d/chemistry/1/5/p/9/1/uranium-glass-fluorescence.jpg&imgrefurl=http://chemistry.about.com/b/2010/03/15/uranium-glass-see-the-glow.htm&usg=__tSsF1ke6RLKFjdmmUMT0aSiTTu0=&h=300&w=400&sz=45&hl=en&start=1&um=1&itbs=1&tbnid=xnVCmk_KbUunbM:&tbnh=93&tbnw=124&prev=/images%3Fq%3Dgreen%2Buranium%2Bglass%26um%3D1%26hl%3Den%26safe%3Doff%26client%3Dfirefox-a%26hs%3DAWk%26sa%3DN%26rls%3Dorg.mozilla:en-US:official%26tbs%3Disch:1

Graphite, when it becomes hot enough, begins to emit sufficient blackbody radiation in the visible spectrum to be seen by the naked eye. That is, if you heat it hot enough, it will glow red, just like other materials do, such as iron or steel. Heat the graphite to even higher temperatures, and it will begin to glow white hot.

The red glow that was seen at Chernobyl was simply red-hot graphite, which was heated to such high temperatures by the decay heat of the fission products in the core.

        Daniel said:

The green color of radioactive material that suggests “radioactivity” is grounded in reality, but has nothing to do with “radioactivity” and everything with uranium: There was a time when uranium ores were used in the process of glass making (no joke). And the color of this uranium glass is a spectrum from lightish yellow to intensive “radioactive” green. The glass is not radioactive (ok, a little bit, but the natural radiation from the sun etc. is far more intensive) but when the right light shines on it, it looks really nice (just google for images).

Yes I have a small collection of marbles, acquired in my youth that are made of uranium glass. Transparent in ordinary light, they do glow green under UV. Some are milk-white and glow yellow when exposed to ultraviolet. EBay is awash with uranium glass marbles and beads, some made within the last few years.

Uranium glass has utilitarian as well as decorative applications. Its coefficient of thermal expansion happens to make it suitable for graded seals and glass-to-metal seals in glass apparatus, such as vacuum tubes and vacuum capacitors.