Tomato Canners: Should You Use a Pressure Canner or Hot Water Bath?

There are two types of tomato canners most commonly used in processing tomatoes from the home garden: pressure canner and boiling water bath canner (also called hot water bath canners). There are advantages to each.

A tale of two tomato canners

Here’s a brief description of both tomato canners and how they work.

Pressure canner. A pressure canner is a heavy pot with metal flanges on both the top pot rim and lid rim (for a tight seal), a pressure vent on the lid, and a pressure gauge. The pressure canner’s rack sits in its interior bottom and holds filled jars sitting in 2-3 inches of water. The lid flanges are lined up with canner flanges and turned to create a tight seal. When heated, the water becomes steam. Pressure builds. The vent is closed, sealing the pot. Steam expands, making both pressure and temperature rise to process tomatoes. Note: a pressure canner is different than a pressure cooker.

Water bath canner. A hot water bath canner is a deep, tightly covered metal pot with a rack or basket in the bottom. The canner is deep enough to hold quart jars plus an inch or two of water to cover them and a couple of excess inches above that for boiling water. Filled jars are placed in the canner. Water is brought to a boil over jars to process tomatoes.

The problem with canning tomatoes and tomato canners

Tomatoes face two potential dangers when canned at home: bacteria, specifically Clostridium botulinum (which can live in improperly preserved foods and causes botulism) and other molds, yeasts, and enzymes which can cause tomatoes to decompose and lose flavor.

Clostridium botulinum bacteria do not flourish in high acid foods – those foods have a pH below 4.6. The problem is that tomatoes are a borderline acid food.

Some varieties are more acidic than others. You can fix your problem of acidity easily by simply adding add 2 tablespoons of bottled lemon juice or 1/2 teaspoon of citric acid per quart of tomatoes when you can.

So when you decide between tomato canners, you need to decide whether or not you need to add lemon juice or citric acid to the tomatoes when using a boiling water bath canner, or avoid that step altogether and use a pressure canner.

Both canners work safely

Tomatoes can be processed safely using either type of canner. The boiling water bath method is safe because boiling water (212º F) inactivates enzymes, and in adding citric acid or lemon juice is an insurance policy in making tomatoes a high-acid food. A pressure canner can be used for both low-acid and high-acid tomatoes because it processes foods at high temperatures.

Advantages to each kind of canner

Pressure canner advantages

Versatility. Pressure canners can be used to process both high-acid and low-acid foods. Water in a pressure canner can be heated to a temperature of 240º F, which foils any tomato issues with bacteria, mold, yeast, and enzymes. You don’t need to add citric acid or lemon juice to lower tomatoes’ acidity. While the pressure itself does not destroy the organisms, the heat does.

(Find a selection of pressure canners here.)

Hot water bath advantages

  • Easy to use. Boil water. That’s pretty much it … no worries about checking pressure or venting the canner.
  • Cost. Boiling water bath canners are less expensive than pressure canners.
  • Versatility. Some cooks use any kind of large pot, with a rack, as a hot water bath canner.
(Find a selection of hot water bath canners here.)

Disadvantages of each kind of canner

Pressure canner disadvantages

  • Cost. Pressure canners can be more expensive than hot water bath canners.
  • Venting. You need to be careful to vent the canner for 10 minutes before processing time begins. Trapped air lowers the canner’s internal temperature, since canners cannot vent during processing. Lower temperatures will not safely process products. Internal canner temperatures are lower at higher altitudes, too, so you need to be careful to monitor venting carefully.

Hot water bath canner disadvantages

  • Limited use. Can only be used for high-acid foods, or you need to adjust the foods’ acidity.
  • Extra ingredients. Since tomatoes are borderline acidity, you need to add lemon juice or citric acid before processing them in a boiling water bath.
  • Size. Some hot water bath canners (or pots that substitute for one) do not have a flat bottom or are excessively wide. When used in the home on an electric range, a water bath canner or pot requires a flat bottom. Its circumference should not exceed 4 inches beyond the heating element.


Get more tips on our Canning Tomatoes Pinterest board.


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