Description

A Mason jar, named after John Landis Mason who first invented and patented it in 1858, is a molded glass jar used in home canning to preserve food. 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 aluminium disc-shaped lid against the jar’s rim. An integral rubber ring on the underside of the lid creates a hermetic seal. The bands and lids usually come with new jars, but they are also sold separately. While the bands are reusable, the lids are intended for single use when canning. Largely supplanted by other products and methods for commercial canning, such as tin cans and plastic containers, glass jars and metal lids are still commonly used in home canning. Mason jars are also called Ball jars, in reference to the Ball Corporation, an early and prolific manufacturer of glass canning jars; fruit jars for a common content; and glass canning jars a generic term reflecting their material and purpose. Lightning fruit jars, another type of Mason jar, was not as common as the screw-thread version, but they were popular for home canning in the late nineteenth and early twentieth centuries.