One of the most reliable ways to identify Fostoria glassware is to expose it to black light, under which it glows a pale yellow. Other glassware that is commonly mistaken for Fostoria does not glow beneath black light.
There are many tests that can be used to help to identify Fostoria glassware. Fostoria is commonly mistaken for Whitehall glassware, so many of these tests focus on the differences between Fostoria and Whitehall glass. A key indicator of Fostoria glass is exceptional clarity. Fostoria fire-polished each piece, producing a clear, smooth surface. If the surface of the glass is rough or wavy, it is likely that the piece is Whitehall.
Other tests rely on the shape of the piece and its stylistic features in order to determine the manufacturer. Fostoria pieces with handles, for example, have handles which connect to the body of the piece at the very top edge. Whitehall pitchers and jugs have handles which connect an inch or so below the lip. Vertical pieces of Fostoria tend to curve more than pieces produced by other manufacturers. Fostoria usually flares out at the top, where Whitehall pieces tend to be more straight-sided. Generally, Whitehall is composed of simpler, straighter shapes.