I bought a blacklight yesterday and was curious to see if it would make any of my bottles glow in the dark. As it turns out, a lot of them do glow yellow-green. Does anyone know what is in the glass that makes them glow? Uranium makes glass glow, but it wouldn't be that, would it? Most of the bottles I have that glow are clear, and date anywhere between 1820 and 1910. Some of my aqua, sun-colored amethyst, and peacock blue bottles also glow. Have any of you tried a blacklight on your bottles?