Collectors Weekly, is glass with uranium oxide added to produce a yellow-green color. Glass that is of this color but not clear is not considered vaseline, or uranium, glass. Some makers also added iron oxide to give a brighter green and less yellow appearance to the glass.
But many pieces of old glass may have a faint green glow even if uranium was not used in the making.
These pieces, for example:
Just a faint green glow around the edges
of this Melrose compote made around 1887 by Dugan Glass (and found by me for $3!):
The green color of this tri-corner bowl glows only faintly
and its color suggests the addition of something to tone down the yellow:
A surprise was the quick, rich glow on these,
two candleholders that I believe are Heisey, but have not been able to verify. They are my usual ones on the table--I love the way they catch light. Right now they're waiting to be put away, as soon as I clean up that china closet:
Another older piece I have not yet identified as to year or maker is this bud vase, modestly glowing (and dusty) in its corner:
Glassmakers prior to about 1916 (some say 1914) also sometimes added manganese to the glass to get rid of the "coke bottle green" appearance of their clear glassware. Such glass can also glow in a black light. Glass with manganese is also subject to "sun purpling," as it will turn various shades of lavender or purple if left too long exposed to sunlight. Some dealers today are "cooking" old glass to turn it a deep purple, a practice frowned on by many collectors (myself included) who believe this process spoils the original beauty and authenticity of the glass. I do have some pieces of sun-purpled glass but it happened naturally and probably years before I got them.
Later on, manufacturers also added iron oxide or other chemicals to produce a softer green like the sherbets below, which were made during the Depression years, I believe by Hazel Atlas. Some argue that this is not true vaseline glass, but I don't have a dog in that fight. And they certainly do glow, instantly and brightly!
All this is probably more than you ever wanted to know, but it's only the tip of the iceberg! I am a real novice in this area, learning literally as I type, so check out the links for more information--and for a scientific explanation, try this website that will ease any fears you might have about possible radiation dangers from this glass.
I initially tried checking my glass with a lamp that had a black light bulb but for some reason it did not work at all. But the little flashlight really makes the glass pop with color--and it also lights up the old glass too.
You can have fun yourself seeing how old your glass is by getting a UV flashlight and shining it into your own cabinets. See what's lurking in the corners at your house! (Just don't shine it on your white shirt or you might be dismayed by all the spots and stains it finds!).
Here's the one I bought, and here's a link to where I got it.
Copyright Susanna Holstein. All rights reserved. No Republication or Redistribution Allowed without attribution to Susanna Holstein.