Antique glass vases can be found in a plethora of styles, sizes, designs and colors. The actual type of glass used varies as well, and many of the techniques used to produce antique vases continue to be used by glassblowers and manufacturers today. If you need to identify a genuine antique glass vase, several factors, including markings, design, thickness, and other traits should be taken into consideration.
Study antique carnival glass vases. This inexpensive, iridescent glass, first popularized in the first few decades of the 20th century, was molded with a pattern, then covered with a metallic coating. Check for the name of the antique vase maker, either by looking for an identifying mark or comparing the piece to a similar item. Early carnival glassmakers include Northwood, Fostoria, Cambridge, Millersburg, and U.S. glass. Antique glass tends to be thicker than reproduction material, and the rainbow-type iridescence is evenly distributed throughout the piece.
Check out Depression-era glass vases. During the Great Depression, low-quality clear or see-through colored glass was manufactured by a handful of companies in the Midwest. Fakes tend to be heavier. Look at the patterns issued during this time, including Tulip, Bowknot, Hobnail and CherryBerry. Some patterns were produced by a particular company while others were produced by several companies. Check an antique glass reference book for details.
Search for marks on the glass. If you find a letter stamped on the bottom, check it against a reference book list of companies that produced antique vases. You may need to use a magnifying glass or place the vase under a bright light to find any marks, as they tend to be faint.
Find scratches on the glass. This indicates older glass when the scrapes line the bottom of the vase. If the pontil mark (the dip underneath the glass) appears polished, it proves that the vase was hand-blown by an artisan, not mass-produced by a machine.
Look for antique blown-glass vases. A deep blue vase, hand-blown by a glassmaker in one piece, with a rough pontil mark at the bottom, from late 1700s New England typifies this style. Sometimes designs were etched onto the glass, as in a thin Bohemian blown glass vase on top of a marble base, circa 1850.
Learn to recognize milk glass and other opaque antique vases. The dull coloring in early milk glass, caused by arsenic used in the mixture, differentiates it from fakes. The edges of early milk glass pieces sometimes have red or "fired" edges. Check for fake signatures--the McKee company signature has been faked on some items to trick people into thinking they're original. There's a long curvy "K" in the authentic signature; the replica "K" looks shorter.