Mason jar

A Mason jar, also known as a canning jar, preserves jar or fruit jar, is a glass jar used in home canning to preserve food. It was named after American tinsmith John Landis Mason, who patented it in 1858. The jar's mouth has a screw thread on its outer perimeter to accept a metal ring, or band. The band, when screwed down, presses a separate stamped steel disc-shaped lid against the jar's rim.

After Mason's patent expired, numerous other companies began manufacturing similar jars. Over the years, the brand name Mason became the genericized trademark for this style of glass home canning jar, and the word Mason can be seen on many Ball and Kerr brand jars. Such jars are occasionally referred to using common brand names such as in Ball jar (in the eastern US) and Kerr jar (in the western US), regardless of their actual brands.

Glass canning jars provided a safe, reliable, and economical way to preserve all sorts of foodstuffs for later use and became an essential part of farming culture and home food storage, and preserved foods were displayed at county fairs for judging and awards. The peak use of Mason jars came during World War II, when the U.S. government rationed food, encouraging the public to grow their own. As migration to cities occurred, along with the rise of electrical refrigeration, the more efficient transport of goods made fruit and vegetables available year-round, reducing the need for home canning.

On August 15, 2017, the registrar at National Day Calendar proclaimed National Mason Jar Day, to be observed annually as a national holiday on November 30, beginning in 2017.