Canning jars are one of the most important pieces of equipment in canning. When choosing jars the Mason-type, threaded, home-canning jars with self-sealing lids are the best choice. These types of jars can come in a variety of sizes including:
- Jelly (4 ounces, 118 mL)
- ½ pint (8 ounces, 236 mL)
- Pint (16 ounces, 473 mL)
- 1-½ pint (24 ounces, 710 mL)
- Quart (32 ounces, 946 mL)
- ½ gallon (64 ounces, 1,892 mL)
There are two different opening diameters to glass home-canning jars. One is known as standard and one as wide mouth. The standard mouth jars have an opening about 2-⅜ inches wide. The wide mouth jars have an opening about 3 inches wide which makes them easier to be filled and emptied.
When jars are handled properly they can be reused many times with new lids. Proper handling includes appropriate cleaning, sterilizing, packing and cooling.
Cleaning and Sterilizing Jars
Before each canning, all empty jars should be washed in a dishwasher or by hand. If washing by hand make sure to rinse thoroughly as remaining detergent residue can cause unnatural flavors and colors. If your jar has a white film, aka mineral deposits, create a soaking solution from 1 cup vinegar (5 percent acidity) per gallon of water and soak the jars for several hours, then wash in your dishwasher or by hand.
Some food products, such as jams, jellies, and pickled foods processed less than 10 minutes, must be packed into sterilized jars. To sterilize empty jars submerge them right-side-up in a boiling-water canner with the rack in the bottom. Fill the canner with enough warm water so the water level is 1 inch above the tops of the jars. Bring the water to a boil and boil for 10 minutes. Reduce the heat in the canner but leave the jars in the hot water until it is time to fill them. When ready to pack jars, remove and drain sterilized jars one at a time with a jar lifter, saving the hot water in the canner for processing the jars once they are packed.
If you did not sterilize your jars before packing, submerge them in enough water to cover the jars and then simmer the water until it is time to pack them with food. A dishwasher may also be used for cleaning and preheating the jars if they are washed and dried on a complete regular cycle- make sure to leave the jars in the closed dishwasher until you are ready to pack them with food. Proper cleaning, sterilization (when appropriate), and packing can ensure a long life for your jars.
Cooling Jars
After processing the jars they will be hot when you remove them from the canner. Use a jar lifter to pull the jar from the canner and place on a towel or a rack to cool without causing damage to your countertops. The jars should remain cooling at room temperature for 12 to 24 hours. When you remove the hot jars from the canner do not retighten their lids. If you attempt to retighten the lids the gasket could end up damaged, causing seal failures and spoiled food. If you raw-packed the food you will likely see a lower liquid level after the jar cools; during processing the jars will vent air and the food will shrink. Resist the urge to open the jar and add more liquid; this breaks the seal and will end in spoiled food if placed in storage. If cooled properly these jars can be used many times without fear of weakening or breakage.
Jars Not Recommended for Use
Although attractive, jars with wire bails do not make secure canning jars. Mayonnaise or salad dressing jars that come in pint and quart-sizes used with two-piece lids often have more seal failures and jar breakage. This is due to narrower sealing surfaces and the jars being less tempered than Mason jars. These types of jars may be weakened by repeated contact with metal spoons or knives used in dispensing mayonnaise or salad dressing. Scratches caused by these metal utensils could cause cracking and breaking while processing the jars in a canner. These types of jars are especially not recommended for use in a pressure canner due to 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.