Jars and Lids

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Title: Jars and Lids
Categories: Canning, Information
Yield: 1 guide


Food may be canned in glass jars or metal containers. Metal containers
can be used only once. They require special sealing equipment and are
much more costly than jars.

Regular and wide-mouth Mason-type, threaded, home-canning jars with
self-sealing lids are the best choice (Plate 1). They are available in
1/2 pint, pint, 1-1/2 pint, quart, and 1/2 gallon sizes. The standard
jar mouth opening is about 2-3/8 inches. Wide-mouth jars have openings
of about 3 inches, making them more easily filled and emptied.
Half-gallon jars may be used for canning very acid juices. Regular-mouth
decorator jelly jars are available in 8 and 12 ounce sizes. With careful
use and handling, Mason jars may be reused many times, requiring only
new lids each time. When jars and lids are used properly, jar seals and
vacuums are excellent and jar breakage is rare.

Most commercial pint- and quart-size mayonnaise or salad dressing jars
may be used with new two-piece lids for canning acid foods. However, you
should expect more seal failures and jar breakage. These jars have a
narrower sealing surface and are tempered less than Mason jars, and may
be weakened by repeated contact with metal spoons or knives used in
dispensing mayonnaise or salad dressing. Seemingly insignificant
scratches in glass may cause cracking and breakage while processing jars
in a canner. Mayonnaise-type jars are not recommended for use with foods
to be processed in a pressure canner because of excessive jar breakage.
Other commercial jars with mouths that cannot be sealed with two-piece
canning lids are not recommended for use in canning any food at home.

JAR CLEANING:
Before every use, wash empty jars in hot water with detergent and rinse
well by hand, or wash in a dishwasher. Unrinsed detergents may cause
unnatural flavors and colors. These washing methods do not sterilize
jars. Scale or hard-water films on jars are easily removed by soaking
jars several hours in a solution containing 1 cup of vinegar (5 percent
acidity) per gallon of water.

STERILIZATION OF EMPTY JARS:
All jams, jellies, and pickled products processed less than 10 minutes
should be filled into sterile empty jars. To sterilize empty jars, put
them right side up on the rack in a boiling-water canner. Fill the
canner and jars with hot (not boiling) water to 1 inch above the tops of
the jars. Boil 10 minutes at altitudes of less than 1,000 ft. At higher
elevations, boil 1 additional minute for each additional 1,000 ft.
elevation. Remove and drain hot sterilized jars one at a time. Save the
hot water for processing filled jars. Fill jars with food, add lids, and
tighten screw bands.

Empty jars used for vegetables, meats, and fruits to be processed in a
pressure canner need not be presterilized. It is also unnecessary to
presterilize jars for fruits, tomatoes, and pickled or fermented foods
that will be processed 10 minutes or longer in a boiling-water canner.

LID SELECTION, PREPARATION, AND USE:
The common self-sealing lid consists of a flat metal lid held in place
by a metal screw band during processing. The flat lid is crimped
around its bottom edge to form a trough, which is filled with a colored
gasket compound. When jars are processed, the lid gasket softens and
flows slightly to cover the jar-sealing surface, yet allows air to
escape from the jar. The gasket then forms an airtight seal as the jar
cools. Gaskets in unused lids work well for at least 5 years from date
of manufacture. The gasket compound in older unused lids may fail to
seal on jars.

Buy only the quantity of lids you will use in a year To ensure a good
seal, carefully follow the manufacturer's directions in preparing lids
for use. Examine all metal lids carefully. Do not use old, dented, or
deformed lids, or lids with gaps or other defects in the sealing gasket.

After filling jars with food, release air bubbles by inserting a flat
plastic (not metal) spatula between the food and the jar. Slowly turn
the jar and move the spatula up and down to allow air bubbles to escape.
Adjust the headspace and then clean the jar rim (sealing surface) with a
dampened paper towel. Place the lid, gasket down, onto the cleaned
jar-sealing surface. Uncleaned jar-sealing surfaces may cause seal
failures.

Then fit the metal screw band over the flat lid. Follow the
manufacturer's guidelines enclosed with or on the box for tightening the
jar lids properly.

Do not retighten lids after processing jars. As jars cool, the contents
in the jar contract, pulling the self-sealing lid firmly against the jar
to form a high vacuum.

* If rings are too loose, liquid may escape from jars during processing,
and seals may fail.

* If rings are too tight, air cannot vent during processing, and food
will discolor during storage. Overtightening also may cause lids to
buckle and jars to break, especially with raw-packed, pressure-processed
food.

Screw bands are not needed on stored jars. They can be removed easily
after jars are cooled. When removed, washed, dried, and stored in a dry
area, screw bands may be used many times. If left on stored jars, they
become difficult to remove, often rust, and may not work properly again.

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* USDA Agriculture Information Bulletin No. 539 (rev. 1994) MM by km

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