Both green Depression glass and Vaseline glass will glow under a black light due ​to the uranium oxide content in the glass. Old Burmese glass fluoresces a similar yellow-green color. American colorless pressed glass made before 1930 is said to fluoresce yellow, while reproductions generally do not.

How do you make Depression glass glow?

The small amount of uranium dioxide not only gives the glass its color, but it also makes it glow. When you place a piece of glass you believe to be vaseline in a dark area and illuminate it with a blacklight, it should fluoresce bright green.

How can you tell if Depression glass is uranium?

Perhaps the most reliable way to identify the presence of uranium in the glass is to expose it in the dark to a source of ultraviolet light (e.g., a black light). If the glass glows a rich green color, it contains uranium.