Canning Jar Preparation

These guidelines must be followed for the safe handling and use of home canning jars.

Selection and Cleaning

All jars must be visually checked for nicks, cracks, uneven rims and other damage or defects. Once you have determined the jars will be using are in good condition, wash all -- new and previously used -- jars in hot, soapy water. A dishwasher may be used for washing the jars. Do not use brushes with wire components, steel wool, or abrasive materials or cleaner; they are likely to damage or weaken the glass.

Some jars accumulate a white film on the exterior surface. Film build-up can be caused by mineral deposits and may be easily removed by washing or soaking the jars in a solution of 1 cup vinegar to 1 gallon of water. Rinse jars thoroughly. Add 1/4 cup to 1/2 cup vinegar to the canner when processing jars to help prevent film build-up. If the film is not removed with the vinegar wash, it may have been caused by an etching of the glass. Etching results from friction on the surface of the jar which occurs with repeated cleaning and processing. Etching cannot be removed.


The heating methods described below are the only methods recommended for heating jars before filling.

Jars must be heated for 10 minutes before filling to prevent jar breakage. Submerge jars in enough water to cover. Bring water to a simmer (180°F), keeping jars in simmering water until ready for use. Remove jars one at a time as they are needed for filling. Jars can be heated in a saucepot on a cooktop or in a slow-cooker that has a temperature control that can maintain 180°F.

A dishwasher may also be used for heating jars. Jars should be washed and dried using a complete regular cycle. Keep jars in the closed dishwasher removing one at a time as needed.

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