How Does Water Bath Canning Work


Water bath canning is a simple process. It works like this: the high heat of the water drives out the air that is within the tissue of the foods as well as the air that was trapped during the packing process. This creates a vacuum within the jar, which makes the rubberized flange on the lid suck down onto the jar rim and creates a seal. The rim of the jar must be clean before placing the lid on. If you are making a recipe with oil in it you need to clean the rim with a paper towel  that has some vinegar on it to cut the oil. If you are making a recipe without oil you can clean the rim with paper towel that has hot water on it. Once the processing time is complete and the jars are ready to be removed from the canner, using a jar lifter, stand jars upright on a dry towel or cutting board. Space the jars 1 to 2 inches apart so they will cool at an even rate. Allow them to cool 12 to 24 hours. Prevent exposure to extreme drafts or temperature changes that could cause jar breakage.  After you remove jars from the water bath and allow them to cool, you will hear popping noises (this is like music to a canner’s ears)! That’s the sound of the suck and seal. The cooling part of the water bath process is important: the rubber seal will be soft coming out of the water bath and needs to stiffen up to complete the process. The seal process can take up to twenty four hours. If for some reason the jar does not seal, put it in the refrigerator and eat that jar’s contents first. If many jars have not sealed, you can open all of the jars and start over by washing and sterilizing the jars, re-heating the food and following the recipe process time in the water bath again.

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Half Full


I received another great question from a student. Their question was, “When I’m canning and I only have enough food left to fill half of a jar, do I process that jar that is only filled up half way?” The answer is no. Every recipe has a head space recommendation which needs to be carefully followed. As a general rule, leave 1 inch of head space for low-acid foods like vegetables and meats (when you are pressure canning); leave 1/2 inch head space for high-acid foods like fruits, tomatoes, pickles, and relishes; 1/4 inch head space for jams and jellies. Care must be taken when filling jars to the correct head space. To much air can turn food a dark color and may cause it to begin to mold. To much food in a jar can cause the jar to break in the water bath during processing. If you have a jar that is only half full, put it in the refrigerator and eat it first.

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