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Over the years, many types of jars with many varieties of seals have been used for home-canning. The most commonly used jars bear the names of Ball and Kerr and are commonly referred to as Mason jars. They use a two-piece cap to produce a vacuum seal in the jar after heat processing.

To ensure safe home-canning, use only jars that are approved for home-canning and made from tempered glass. Tempering is a treatment process for glass that allows the jars to withstand the high heat (212 degrees) of a water-bath canner, as well as the high temperature (240 degrees) of a pressure canner, without breaking.

Home-canning jars come in many sizes: 4-ounce, half-pint, 12-ounce, 1-pint, and 1-quart. They offer two widths of openings: regular-mouth (about 2½ inches in diameter) and wide-mouth (about 3⅛ inches in diameter); see Figure 2-10. Regular-mouth jars are used more frequently for jelly, jam, relish, or any other cooked food. Wide-mouth jars are mainly used for canning vegetables, pickles, and meats, because it’s easier to get the large pieces into the wide opening.

FIGURE 2-10: Varieties of canning jars: wide-mouth, regular-mouth, and jelly jars.

Some canning jar companies offer half-gallon jars, but they are not USDA or Cooperative Extension System approved for safe canning. However, these larger jars make excellent containers for dehydrated foods.