Glass that will glow in a UV light; Under the Hammer.
VASELINE Glass was primarily made before WWII and one of the primary ingredients was uranium.
Under an ultra-violet lamp, vaseline glass will glow. The high energy emissions of electrons from the UV light cause the uranium oxide particles in the vaseline glass to become unstable, causing this fluorescence.
We like to describe the effect as causing the vaseline glass to look like it has exploded in flames.
No other transparent antigue glass will glow, thus making vaseline glass uniguein the antigue world as it can always be verified to be true vaseline by using a black light. There is no other compound added to glass which will cause this effect except uranium. The yellow green glow is characteristic of uranium-bearing glass and will also occur with custard glass. The latter, however, is easily distinguished from vaseline glass as not transparent.
Vaseline glass can be difficult to detect by the human eye alone and even the best expert can be fooled. Only by testing with the UV light will a piece be identifiable.
Vaseline glass can be yellow, yellow green or green. Individual collectors each have their own preference as to the exact colour of vaseline glass collected. However, as glassmakers of the 1920s-30s added iron to their urnanium oxide dyes to put a green tint intotheirglass and although these pieces will fluoresce under UV light, it is our opinion that green vaseline glass (with no trace of yellow) is only a forerunner of depression glass rather than true vaseline glass.
The government confiscated all supplies of uranium during WWII and halted all production of vaseline glass. Only in lateryears after nuclear testing etc was banned did the government ease restrictions and allow a very small supply of uranium to glass companies to resume production of vaseline glass.
As uranium supplies are closely monitored by the government and tightly distributed between various glass companies, even more recent pieces of vaseline glass are highly sought after by collectors as each is of a very limited production.
How safe is vaseline glass?
Firstly, the colouring agent is not the unstable and radioactive uranium but the more stable uranium dioxide.
Secondly, it is only 1% to 2% per volume of theglass.
Finally, and most importantly, glass, being a solid, is a barrier to radiation and there is an insignificant amount of radiation anyway from vaseline glass, roughly egual to standing in sunshine.