The jar is then allowed to cool to room temperature.
The cooling of the contents creates a vacuum in the head space, pulling the lid into tight contact with the jar rim to create a hermetic seal.
Once cooled, the band is removed to prevent residual water between the jar threads and the lid from rusting the band.
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. brands of Mason jars are Ball, Kerr, and Golden Harvest.
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. They are also produced in a variety of volumes, including cup (half-pint), pint, quart, and half-gallon. Jarden Corporation, based in Boca Raton, Florida, In home canning, food is packed into the jar, leaving some empty "head space" between the level of food and the top of the jar.
The lid is placed on top of the jar with the integral rubber seal resting on the rim.
A band is screwed loosely over the lid, allowing air and steam to escape.The jar is heat sterilized in boiling water or steam and the lid is secured.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 steel disc-shaped lid against the jar's rim.An integral rubber ring on the underside of the lid creates a hermetic seal.