Yellow to yellow-green glass that turns florescent bright green (under UV light) is the only true verification of
Vaseline Glass!  This link shows various pieces under a blacklight:

UV BLACKLIGHT FUN PAGE!

How do I become a member?
CLICK HERE
for a membership application!

Vaseline Glass collectors primarily collect yellow or yellow-green glass. (A controversy will probably go on forever regarding Green Depression glass, as Jay Glickman included some examples of green glass in his reference book). Individual collectors each have their own preference as the the exact color of Vaseline Glass collected. Most people primarily collect the glass that is more toward the yellow end of the spectrum, but some collect anything that 'Glows'. (Other glass that glows includes some green depression glass; Burmese glass - both old and new; and custard glass, ranging from the pale off-white to the bright green. Each one of these types 'Glow' due to the addition of Uranium Dioxide to the glass formula.)
DEFINITIONS CAN BE CONFUSING:
Members of the VGCI consider vaseline glass to be yellow or yellow-green (depending on if it is in room light or daylight).  A glass dish can look yellow under incandescent lighting, but when it is taken outdoors, the UV of the sun will tickle the atoms, making the same piece look yellow-green.  Also, when a flash camera is used on vaseline glass, it will make it appear more green than the eyes do, because the intense flash also 'tickles' the uranium atoms.  Vaseline glass (in the USA) is defined by the VGCI to be yellow first and glow green under a blacklight second.  Other countries have their own definition for vaseline glass.  For instance, people in Australia use the words, 'vaseline glass' for any type of glass that has an opalescent rim.  What we consider (in the USA) to be vaseline glass, they call citron or uranium glass.  The British in the United Kingdom refer to glass that has a whispy opalescent treatment to be vaseline glass.  What they call 'Primrose Pearline' (a trade name from Geo. Davidson & Son) is what the US collectors call 'vaseline glass'.  In Germany, they did not differentiate and call all of it 'uranglas' and it can be yellow or green, as long as it has uranium in it and glows under a blacklight.  Many sellers on eBay will list green depression glass under the 'vaseline glass' heading, knowing that vaseline glass brings more money than green depression glass.  True vaseline glass does not have iron oxide added to the formula, which makes green depression glass a separate formula, and thus, is not considered to be vaseline glass.

Vaseline Glass is not harmful, as the emissions from the glass are just slightly stronger than
normal background radiation that we are all exposed to on a daily basis.

Vaseline Glass was primarily made from 1840, up to just before WWII,  and then was continued from 1959 to the present.  Current manufacturers include: Fenton Glass and Mosser Glass, as well as some small independent shops such as Gibson Glass and Jack Loranger (HotGlass.cc). Vaseline Glass was in its' heyday during the Victorian period from the 1880's to the 1920's. The yellow-green glass did not sell as well as other colors of glass, so during the depression years, glass manufacturers started adding more iron oxide (commonly known as RUST) to the glass mixture (but still included the Uranium Dioxide) and this had the effect of making the glass more green. Because of this, most green depression glass will glow.  The government confiscated all supplies of uranium during WWII and halted all production of Vaseline Glass from approximately 1943 until the ban was lifted in Nov. 1958.

Only after years of testing by the various regulatory departments of the government were glass companies once again allowed to make this glass.  In Victorian times, glassblowers who made Vaseline Glass usually died at a relatively young age of lung cancer, and the 'stories' have persisted for years that this was due to their exposure to molten Vaseline Glass. However, when this information was discussed with different experts on radiation (from University of Missouri and University of Oklahoma), they felt that there may have been other reasons for their early demise, as radiation tends to affect the thyroid glands the most.  I guess this will also be a subject for long debate.

Due to the tight regulations on Uranium Dioxide and the expense of this ingredient, only very limited quantities are being produced today. Due to this, most collectors are aware of the limited nature of its' production and this is reflected in the marketplace.
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