A boiling water canner is a kitchen device that allows you to safely sterilize canned or preserved foods so that you can be assured of their ability to keep well without refrigeration. There are a couple of types. Some boiling water canner styles feature a pot and a wire or metal rack that can hold several mason or glass jars. Others merely refer to the metal rack, which can be place in any large pot to boil and thus kill any bacteria that might be present on the jars or their lids.

When jars have been filled with any type of food you wish to can, like jam, pickles or sauerkraut, the jars are place in the rack, and then in the pot. Water is poured into the boiling water canner and should cover the jars by at least an inch (2.54 cm). Each type of canned food will have different recommendations for the necessary boiling time. You can check updated cookbooks with recipes for canning for the safest recommendations.

Once the boiling water canner sterilizes the exterior of the jars, they are removed, and allowed to cool before being stored. Many people also use the boiling water canner to sterilize jars prior to filling them with food they want to preserve. This is an excellent idea, since bacteria in the jars can lead to deterioration of foods even if they are boiled in the boiling water canner after being sealed.

It’s important to note what kind of stove you have when choosing the right boiling water canner for your home. First, electric burner stoves must use pots with flat bottoms so that water heats evenly. Second the pot’s diameter shouldn’t be any more than four inches (10.16 cm) larger than the diameter of your cooking surface or burner, either electric or gas. Again the jars in the boiling water canner may not evenly heat and you won't be able to guarantee the safety of your canned food.

In addition to buying a boiling water canner, you may also need to purchase a jar lifter, a device that will remove the rack from the pot once the jars have been boiled for the appropriate time. Jar lifters sometimes are sold with the boiling water canner, but may need to be purchased separately. Having one is an important step in personal safety, since you’ll be removing jars from very hot water.

Some boiling water canner styles are versions of pressure cookers and must be used with due caution. What is most important is waiting to remove the jars, and release pressure per the instructions for your canner. Many of the newer models take less waiting time. If you’re using an older pressure cooker as a boiling water canner, you should wait 30 to 45 minutest to depressurize.

Some people might ask why you can’t just set jars in a pot to boil and sterilize them. It’s true that you might get away with this method. Yet the great thing about the rack in the boiling water canner is that it keeps the jars off the bottom of the pot so that boiling water can circulate underneath them, and it keeps the jars separated from each other so that they don’t come together and accidentally break. Using a boiling water canner is therefore safer, more effective, and less likely to result in losing the very food you wish to preserve.