Word of the Week: Vaseline Glass

 A Northwood, Carnival glass vaseline Heart & Flowers plateAs I’ve discussed here before, terms commonly get conflated and misused, only to end up with a much wider application than is accurate. “Vaseline glass” is yet another example of this. More properly termed uranium glass, this glass has had uranium added to the mixture that is then melted down, colored and formed into glassware. Most pieces have only trace amounts, definitely less than 2% by weight, of uranium, although some pieces were nearly 25% uranium by weight. Uranium glass normally appears on the yellow-green spectrum, depending on the influences of the uranium and other colorants used, but regardless of the color in natural light, it fluoresces in a vibrant green shade when placed under ultraviolet (“black”) light.

The “Vaseline” part was originally applied to a particular pale yellowish-green transparent/semi-transparent shade of uranium glass as it was thought to look like the 1920s version of Vaseline and other petroleum jelly, but over time, it’s come to be used, particularly in the US, for uranium glass in general and sometimes, particularly sloppily, even for any glass in that same yellow-green color range, regardless of whether or not it fluoresces. Properly, it is simply a subtype of uranium glass, as are custard (pale yellow), jadite (pale green) and Depression glass (which is also pale green but transparent/semitransparent vs opaque/semi-opaque). (Depression glass is, clearly, another one of those terms, as it often is applied to any glassware, particularly any colored glassware, produced during the years of the Depression.)

There’s nothing new about uranium glass, as archaeology dates it back to 79 AD and it was also used in European glass production for centuries, but it really began to boom in the 1800s, reaching its peak during the late 19th century and early 20th. Uranium glass production, table- and housewares, had slowed considerably by the start of World War II, but when the use and availability of uranium was heavily restricted and controlled during the end of the war and throughout the Cold War, the manufacturing of uranium glass took a dip that it never really recovered from, although there are still those today who work with uranium glass.

As with all glass, color, condition, maker, pattern, and form all play a role in the value uranium or vaseline glass brings at auction.