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How to Value a Glass With No Marks

Before 1675, drinking glasses were relatively rare. Glasses from this era were made from "soda glass," a blend of soda and silica, which had two disadvantages -- it broke easily and it had a cloudy appearance. But in 1674, an Englishman called George Ravenscroft, patented "lead glass." This was very tough, much more transparent and it could be decorated in a variety of ways. Most drinking glasses carry no identifying marks whatsoever, so they have to be valued according to signs of handcraftsmanship, age and decorative appeal.

Instructions

- 1
  Look to see whether a glass has been hand-blown -- that is, made individually by a craftsman -- or press-molded by machine. A hand-blown glass will have a small blemish in the middle of the base known as a "pontil mark." This is where the glass-blower's rod was originally attached to the molten glass. You can identify press-molded glass by looking for seams, a rolled-bottom edge and impressed serial numbers. A press-molded glass with have little or no value. A glass that is hand-blown will have a chance of being valuable, but only if it has other features as well.
- 2
  Assess the age of the piece by looking at its design. On older drinking glasses -- whether for wine or other beverages -- the foot tends to be much wider than the bowl. There are collectors of antique drinking glasses, so this is a positive sign of value.
- 3
  Check the item for decorative appeal. The bowls of the finest antique drinking glasses would be hand-engraved with pictorial vignettes. Look particularly for a vignette that is dated with a year, or one that commemorates some particular historical event or personality -- these add greatly to the value of a piece. Also check the stem for what is known as a "spiral twist." This is a lattice of opaque glass running up the inside of the stem. Glasses with this feature are highly collectible.

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