Collectors Guide to Mason Jars

Mason jars were used in home canning to preserve food. While these jars are still manufactured today, collectible and antique examples date back to the mid 17th century. Once a very popular way to store and preserve food, home canning fell out of favor when commercially canned foods became widely available after World War II. However, the humble mason jar has become a desirable vintage collectible.

These jars take their name from John Landis Mason. Mason was a young inventor who came up with the concept of a metal screw-on lid in 1858. The threaded neck on glass jars that we take for granted today was once a major innovation. Mason's developments made preserving food at home much easier and made the jars reusable. Despite the fact that Mason sold five of his glass canning jar patents in 1859, his name had staying power. The mason jar is the common name for glass home canning jars to this day.

Mason canning jars come in a variety of sizes from the large half gallon size to the tiny one cup size. The quart size mason jar is the most common, but the pint sized jar is popular as well. Jars may be standard or wide mouthed and were once made in a variety of colors, although modern mason jars are manufactured using clear glass. Colors include emerald green, rare cobalt blue, amber, milk glass and aqua. The thinking behind producing jars in various colors was that the colors would help to protect food from spoiling. Closures vary as well and include screw on metal lids or E-Z seals. E-Z seals were glass lids with rubber gaskets and a metal sealing device attached to the jar. Companies that manufactured mason jars included Jarden Home, Atlas, Kerr, Ball and Mason.

While many jars carry an embossed date of 1858, most do not date back that far. Jars that carry this date may have actually been manufactured as late as 1920. Before 1915 mason jars were made from blown rather than molded glass. Blown glass jars have a round raised area, or pontil scar, on the bottom while molded glass exhibits telltale mold seams. Blown glass jars are more valuable than molded ones. Values of collectible mason jars may range from around $6 to $10 all the way up to hundreds or even thousands of dollars. Having the original lid with the jar can increase the value by as much as 50 percent. The best way to determine value of an individual jar is to consult a collecting reference such as "The Redbook of Fruit Jars" by Doug Leybourne.

Reproductions of some of the most valuable mason jars date back almost 40 years. The base mold numbers on these jars often read 1171, 851 or 971. These fakes were created as poor impersonations of some of the more valuable mason jars in colors such as cobalt blue, lime green and milk glass. Ironically, many of these reproductions have become popular with collectors and may sell for $70 or more. Potential buyers should be aware that the technology of altering the color of glass through irradiation has allowed unscrupulous sellers to change the appearance of mason jars that were originally clear glass.