Home canning

Though ceramic and glass containers had been used for storage for thousands of years, the technique of canning, which involves applying heat for preservation, was only invented in the first decade of the 1800s.

Home canning glass jars are annealed during manufacture to increase their ability to withstand temperature changes and mechanical shocks.

Water bath canning is appropriate for high-acid foods only, such as jam, jelly, most fruit, pickles, and tomato products with acid added.

The heat is turned off, pressure reduced, canner opened, and hot jars carefully lifted out and placed on an insulated surface (towels, wood cutting board, etc.)

[7] Safety measures must be taken when performing home canning, since ingestion of toxin in food produced by Clostridium botulinum can cause death.

[8] Because of the high risk of illness or death associated with improper canning techniques, the United States Department of Agriculture (USDA) considers it critical that consumers who intend to can at home obtain proper and current information from a reliable source.

The lid also incorporates a slightly dimpled shape, which acts as an indicator of the vacuum (or lack thereof) inside a sealed jar.

Another method that is no longer recommended was the use of layer of hot paraffin wax poured directly over the top of the food (especially jams and jellies) to seal it from air, thus reducing growth of aerobic microorganisms like mold.

This system uses glass jars, single use seals, metal lids, and a water bath canning sterilization process.