Identifying Depression Glass is best approached by learning the seven main glass companies that produced it and the patterns and colors produced. Also be aware that there are reproductions out there, but they are made using a different production method which leaves different identifying marks. They are also usually produced in different colors than the original production set. The original Depression glass was cheaply made and has flaws and marks from the molds and cooling process.
The glass of this period is broken down into two different types, Depression glass and Elegant glass. Depression glass and Elegant glass differ in that Elegant glass had hand-finishing work done to it after it was removed from the mold. This included removing mold marks, grinding the bottom for flattening, and etching or engraving the piece. Elegant glass was made by a smaller number of companies because the hand finishing decreased profit margins. Depression glass is further broken down into 'known patterns' and 'generic glass.' Known patterns have been well documented. Generic glass was made during the Depression glass period but it does not fit into a named pattern designation.
There were seven main companies producing glass during the period from about 1923 through the mid 1940s. These were Federal Glass Company, Hazel-Atlas Glass Company, Hocking Glass Company, Indiana Glass Company, Jeanette Glass Company, MacBeth-Evans Glass Company and U.S. Glass. These companies usually did not put any identifying marks on the glass such as a logo stamp. The only way to identify the maker is know which company made the pattern you are interested in. Occasionally the smaller companies who made Elegant glass would use a logo stamp, but it was not common.
There are 92 different patterns that have been well documented for the Depression glass collector. These include Adam, American Sweetheart, Block Optic, Cherry Blossom, Dogwood, Floral, Georgian, Hobnail, Lake Como, Manhattan, Starlight, and Windsor as a brief sampling. The best way to identify these patterns is find pictures of them so you know what they look like. Some of the names are fairly self-explanatory, such as Cherry Blossom, but most are not.
The most popular colors of glassware were amber, blue, green, pink, and yellow. There were also pieces produced in amethyst, black, cobalt, crystal, cremax, custard, delphite, iridescent, frosted and dark green, ivory, and jadeite.
The best way to determine a genuine piece of Depression glass is to learn the pattern, dates of manufacture, colors the pattern was produced in, and any other known identifying marks. They do not usually have the manufacturer mark stamped on them. One example is the Cherry Blossom pattern by the Jeannette Glass Company. This was introduced in 1930 and produced until 1939. There were 43 pieces in the set and it was made in seven different colors: green, pink, crystal, yellow, ruby, jadeite and dark green. This is one of the most popular collector sets and there are reproductions circulating to watch out for.
Identifying fakes is a matter of knowing exactly what pieces were made for that particular set, and what colors were used. If you know the colors and pieces the pattern was originally produced in, you can identify a reproduction when it does not fit the known data. Cherry Blossom reproductions were first made starting in 1973 with a child's-size butter dish. This was not a piece made by Jeannette Glass Company, as documented by Hazel Marie Weatherman, so it was recognized as a fake.