How to Heat Process Mason Jars to Seal

by Jodi Thornton O'Connell

Canning in mason jars is a great way to keep food preserved without refrigeration. While canning is not extremely complicated, it is very important that you use the correct method for the type of food you are preserving to make sure your canned goods do not expire prematurely. The most common methods of canning are water bath canning, which involves heating and sealing your canned goods on the stovetop with a large pot of hot water, and pressure canning, which requires the use of a pressure canner and more thoroughly heats the canned food.

Tips

  • Acidic foods like pickles and fruits can be heat-processed in a boiling water bath to seal them in mason jars. More alkaline foods like plain vegetables, meat and stews can be safely processed only in a pressure canner that raises the temperature to 240 degrees Fahrenheit to kill bacteria that can cause spoilage.

Get Prepared

Before you start canning it is important that you gather the needed tools and disinfect them properly. Besides your jars, bands and lids you will need a way to handle the hot jars such as tongs or a jar lifter, a wooden spoon and a funnel for filling the jars. Wash out your jars, lids and bands with hot soapy water and rinse them out well. Store your jars in hot--but not boiling--water until you fill them to prevent the jars from breaking after contact with the hot food. Inspect your lids to make sure there are no cracks, chips or sharp edges as this could prevent the jars from sealing properly.

Warnings

  • If you remember Grandma boiling or heating her lids, don't be tempted to do so. The Jarden company changed its lids in 2014 so they can be used at room temperature. Boiling or overheating lids can actually result in damage that will prevent a complete seal.

Tips

  • Check the instructions on the box of lids you plan to use. Those manufactured prior to 2014 will instruct you how to heat the lids if necessary.

Water Bath Canning Technique

Water bath canning is ideal for acidic foods such as fruits, salsa, pickles and chutneys as the acid in the food kills bacteria, negating the need for the high heat of the pressure canner. It is important that you do not can foods with low acidity this way as bacteria could spread in the finished product and cause your food to spoil. You will need a large pot with an inside rack and lid that is deep enough to cover the jars with water.

Step 1

To begin, fill your large pot with rack halfway with water and bring to a simmer.

Step 2

Remove the jars from the hot water with your tongs or jar lifter.

Step 3

Fill them with the acidic food you are canning using the funnel. Be sure to clean off the threads of the jar with a damp clean cloth.

Step 4

Seal your jars and place them in the hot water bath and raise the heat. When the bath is at a rolling boil let the jars process for the time specified in your canning recipe.

Step 5

When your jars have finished the water bath portion of the process remove them from the bath with your tongs or jar lifter and place them upright on a towel (in case any of the jars break from temperature change) and let them rest for 24 hours.

Step 6

Do not retighten the bands while the jars are cooling as this could break the seal on the lids.

Step 7

After your jars have rested check all of the seals to make sure they are airtight and none of the lids have popped up. If your jars are all sealed they can be labeled and stored. Any jars that have not sealed properly can either be refrigerated for immediate use or reprocessed.

Pressure Canning Method

Pressure canning is the preferred method for preserving vegetables, meats and anything that is low in acid content. Use a pressure canner for this method.

Step 1

Heat 2 to 3 inches of water in the pressure canner over medium-high heat and keep it at a simmer until the jars are filled and placed inside. When using a pressure canner, follow the instructions included with your unit as they can vary greatly.

Step 2

Lock the lid of the pressure canner and allow steam to release through the vent pipe for 10 minutes to ensure there is only steam left inside the canner. Close the vent and adjust the heat to the recommended amount of pressure in the manufacturer instructions.

Step 3

Remove the jars from the unit with your tongs or jar lifter after the pressure releases. Set your jars upright on a towel and allow to rest for 24 hours. Check your jar seals, label and store.

Tips

  • Before processing: Leave the amount of headspace recommended by your canning recipe and remove air bubbles with a rubber spatula to release trapped air. Clean the rim of the jar to remove any food that could interfere with a proper seal.

Warnings

  • If you have a glass stove, check with your stove's manufacturer to make sure it is safe for canning. Only use a smooth, stainless steel pot that doesn't extend more than 1 inch beyond the burner's surface.

About the Author

Indulging her passion for vacation vagary through the written word on a full-time basis since 2010, travel funster Jodi Thornton-O'Connell guides readers to the unexpected, quirky, and awe-inspiring.