What Is a Canning Water Bath?

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  • Written By: Christina Edwards
  • Edited By: W. Everett
  • Images By: Natalyka, Jeff Wilson, Chantals, Us Cpsc
  • Last Modified Date: 24 October 2019
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A canning water bath is used in home canning for preserving foods that are highly acidic. This process involves boiling canning jars containing food that is to be preserved. The high water temperature kills bacteria and helps create a seal on the jars. Before being placed into the canning bath, canning jars should be sterilized, checked over for blemishes, and filled with food.

When preserving foods at home, most cooks use a canning water bath. A large pot with a lid and a rack that fits on the bottom of the pot are needed for this. Water is boiled in the pot, and canning jars are placed in it. The rack helps keep the canning jars off of the bottom of the pot, which enables the boiling water to circulate around the jar.

Usually only highly acidic foods can be preserved using a canning water bath. These types of foods, such as berries and apples, have the ability to stop the growth of Clostridium botulinum spores. This bacteria can cause a type of food poisoning that can be fatal. Foods with low levels of acid, such as beans and corn, usually need to be preserved using a pressure canner, which produces higher temperatures needed to kill this bacteria.


Boiling canned food in a canning water bath helps kill other types of dangerous bacteria that can grow in canned food. High water temperatures also help suck oxygen out of the canning jars. This creates a vacuum, which causes the lids on the canning jars to seal. Properly sealed jars will typically keep longer, and they are less likely to allow bacteria into the jars.

To use a hot water canning bath, water should be brought to a boil in the large pot. Enough water should be used, so that the canning jars are covered with a couple of inches (5 centimeters) of water. During the canning process, the water should boil continuously. Since some of the water will evaporate during a canning water bath, an extra pan or teapot of water should also be boiling along with the main pot. This enables cooks to add boiling water to the main pot, if necessary.

Before preserving foods with canning jars, the jars should be sterilized. This can be done by submerging them in hot water, or running them through the sterilization cycle in a dishwasher. They should also be kept hot until they are ready to use, to prevent them from breaking from an extreme temperature change. The rims of the jars should also no have any chips or nicks, since these can prevent the lids from sealing properly.



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