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Canning Tomatoes, Step by Step

Home-canned tomatoes have flavor that simply can't be found with store-bought canned tomatoes. Canning tomatoes is easy, and you put a little bit of summer in every jar.

Canning high-acid vegetables, like tomatoes, using the hot water bath method is easy, fast, and very safe.

Early autumn is a time of year that my wife JoAnn and I look forward to canning time.  JoAnn loves to can peaches, pears, peppers, and especially tomatoes.  Those bright red harbingers of great sauces fill our garden baskets for a few precious weeks and a flurry of canning makes winter a bit easier to face; we have summer in jars.

First, of course, you’ll need to make the sauce, and you probably already have a favorite recipe. If you’re in search of one, try this Fresh Tomato Purée (video).

Preparing the jars

Start the process by checking the jars for any chips around the top edge of the rim where the jar and lid meet.  Anything less than a smooth rim will cause the seal to fail.  Wash the jars with dish soap and water.  Be sure to rinse the jars thoroughly.

Bring a canner full of water to a rapid boil then dip the jars into the water for about 10 seconds to sterilize the jars.  Place the hot jars inverted on a clean cotton dishtowel.

We sterilize as many jars as we plan to use during the canning session.  Once the water in the canner has been used for sealing the jars it isn’t clean enough to use for sterilizing jars.

Washing the jars Sterilizing jars Sterilized jars stored inverted
1. Wash the jars thoroughly before you start. With canning, cleanliness is critical. 2. Sterilize the jars by submerging them in a canner full of boiling water for about 10 seconds. A canning jar lifter with PVC-coated jaws makes the process easy and safe. 3. Place the jars inverted on a clean cotton towel to keep any contaminants out.

Filling the jars

Working quickly is the key to good canning results. Heating the sauce before filling the jars will make the process go quicker and lessens the chance of the jars’ heat-cracking when lowered into the hot water bath. We try to start filling the jars while they’re still warm from the sterilizing process.  We use a canning funnel that has a fill mark molded into the neck.  About a 1/4in. to 1/2in. headspace (empty space between the top of the sauce and the rim of the jar) is necessary to keep the sauce from expanding out of the jar during the hot water bath, ruining the seal.

Filling the jars Funnel showing fill line
4. Heat the sauce before filling the jars.  JoAnn is using a canning funnel for speed and accuracy. 5. The raised rib just above the sauce is the fill mark.

Lids and rings

Sterilize the lids by tossing them into a pan of boiling water for a minute.  Make sure you have enough rings handy. If they’ve been used before check the inside edge of the ring, where it meets the lid, for dents or corrosion that could compromise a good seal.

Before placing the lid on the jar, wipe the rim of the jar clean with a wet paper towel, sauce on the rim will result in a failed seal between the lid and jar.

Sterilizing lids Cleaning jar rim
6. One minute in boiling water will sterilize the lids. 7. A wet paper towel will wipe any sauce cleanly off the rim assuring a good seal with the lid.
REtrieving sterilized lids Installing lid and ring
8. A pair of tongs make retrieving the lids easy.  Magnetic lifters are available. 9. Place the lid on the jar first, then carefully place a ring over the lid and tighten firmly.

The water bath

Water bath canners are inexpensive, long-lasting, and easy to use.  A jar rack makes the process much safer and a whole lot easier.  The rack will hold seven-quart jars above the water for easy loading, and the handles make it easy to lower the jars into and out of the hot water.

Jar rack Jar rack on canner rim
10. The jar rack makes loading the canner easy. 11. Place the rack in its high position in the canner. The water should be just shy of boiling hot.
Loading jar rack Loaded rack
12. Load the jars in pairs, loading in opposing positions to balance the rack and keep it from inadvertently tipping. 13. The loaded rack is ready to be lowered into the hot water.
Immersing rack Water-covered jars
14. Slowly lower the jars into the water. 15. The jars should be covered with at least one inch of water.
Cover the canner 16. Cover the canner, turn up the heat, and when the water starts boiling set the timer for 30 minutes.  Adjust the burner heat to keep the water at a low boil.

Finishing up

When the timer sounds turn off the burner and lift the jar rack to the high position. It’s a good idea to get the jars out of the canner immediately.  Use the jar lifter to remove the jars placing them on a cloth.  I also immediately wipe the standing water off the lid. As the jars, cool vacuum forms under the lid pulling the center of the lid down causing an audible click or snap, a good sound as this assures a good seal has formed. After the jars have cooled check to make sure the lids have sealed.  The lid will be depressed in the center and a light tap will result in a dull thud.  If the lid isn’t sealed you can simply put the jar in the fridge and either use it in the next few weeks or add it to the next batch of canning tomato sauce.

I use a fine point marker to date the jars on the lid making it easy to keep track of my pantry inventory; the oldest dates are used first.

Store your canned goods in a dry, cool, dark place.  Properly stored tomatoes will keep for at least a couple of years and I’ve had some that got lost in the pantry that was still fine after several years.

Lifting rack after processing Removing jars
17. Lift the jar rack to its high position, this makes taking the jars out easier and safer. 18. Lift the jars out of the water with the jar lifter placed below the jar’s lid rim.
Canned tomatoes Checking seal by tapping lids
19. Fresh from the canner.  As the jars cool the lids will seal with an audible click or snap.  Don’t worry, that’s the sound you want to hear. 20. Tap the lids to make sure they are sealed.  A dull-sounding tap means a good seal.
Previous: A Quick Canning Method for Preserving Tomatoes Next: Shelving Common Canning Myths
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