Most of the DISCUS-tubes were made with a greenish glass, sometimes shaded (most of the tubular glass surface), sometimes not.

Those greenish tubes are glowing under UV light and we believe they are made with Uranium glass. Wikipedia: "Uranium glass is glass which has had uranium, usually in oxide diuranate form, added to a glass mix prior to melting. The proportion usually varies from trace levels to about 2% by weight uranium, although some 19th-century pieces were made with up to 25% uranium. ... The normal color of uranium glass ranges from yellow to green depending on the oxidation state and concentration of the metal ions, although this may be altered by the addition of other elements as glass colorants. Uranium glass also fluoresces bright green under ultraviolet light and can register above background radiation on a sufficiently sensitive geiger counter, although most pieces of uranium glass are considered to be harmless and only negligibly radioactive.

The most typical color of uranium glass is pale yellowish-green, which in the 1920s led to the nickname vaseline glass based on a perceived resemblance to the appearance of petroleum jelly as formulated and commercially sold at that time. Specialized collectors still define "vaseline glass" as transparent or semitransparent uranium glass in this specific color.

"Vaseline glass" is now frequently used as a synonym for any uranium glass, especially in the United States, but this usage is not universal. The term is sometimes carelessly applied to other types of glass based on certain aspects of their superficial appearance in normal light, regardless of actual uranium content which requires a blacklight test to verify the characteristic green fluorescence.

In the United Kingdom and Australia, the term "vaseline glass" can be used to refer to any type of translucent glass. Even within the United States, the "vaseline" description is sometimes applied to any type of translucent glass with a greasy surface lustre."