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Here’s how, why and where to test your canning equipment for food preservation season [Extension column, Q&A] | Food

Home food preservation season is beginning, with gardens starting to bloom.

Planning is an important step in the preservation process. To ensure safety, home canning supplies and equipment need to be inventoried and checked before preparing to preserve any food.

To understand a little bit more about why preparing for home food preservation season is so important, especially when it comes to canning low acid foods, I interviewed Martha Zepp to help understand the importance of proper pressure canning and testing pressure canner dial gauges.

Zepp is the home food preservation consultant at Penn State Extension in Lancaster County. She holds a bachelor’s degree in home economics education and a master’s degree in family economics from Penn State University.

Zepp brings a lifetime of experience of canning and freezing foods, and incorporates the scientific knowledge of Penn State University into home food preservation.

Here are my questions and her answers.

How often should dial gauges be tested on pressure canners and why?

Martha Zepp: Testing pressure gauges on dial gauge pressure canners for accuracy should be a routine step done annually in preparing for each new canning season. Over time, as the canner lid is handled, bumped or just used, the calibration of a dial gauge can become inaccurate. If it is off just a little bit, you may not notice the inaccuracy, but it could affect the safety of the canned product.

What is the cost of the test?

The test is free.

Should a dial gauge on a new pressure canner be tested?

Yes, even gauges on new pressure canners and replacement gauges should be tested before use.

What do I need to bring with me to pressure canner gauge testing?

Only the lid is needed for testing. If the gauge has been removed from the canner lid, it can still be tested. While canners should be clean when brought for testing, be careful to avoid getting water into the gauge pipe as the water can affect the test results.

Does a weighted gauge canner need testing?

Pressure canners with a weighted gauge do not need to be tested for accuracy, as the weight cannot go out of calibration. Some pressure canners have both a dial gauge and a weighted gauge. If you have this type of canner, go by the weight when processing. The dial gauge is used to help you know when the canner is near pressure and when it has cooled.

If I have a pressure canner with both a weighted gauge and a dial gauge, can I have my gauge tested?

Yes, we can still test these dial gauges, but you should follow the manufacturer’s instructions for processing using the weight. Use the dial gauge only as a guide on these models. We can still test the gauge. We do not need the weight brought to the testing for these models.

Why should I use a research-tested recipe when canning?

Research-tested recipes for pressure-canned foods are based on set temperatures and the time needed to kill harmful bacteria. Use research-tested recipes from 1994 or more recently. Remember: Sweet corn and snap beans are low-acid foods. All low-acid vegetables, meats and combination foods such as soups need to be pressure canned to eliminate the risk of botulism.

If the pressure is lower than that recommended for processing, the internal temperature of the food will not be adequate to kill all the Clostridium botulinum bacteria and spores. Spores that survive can produce harmful toxins that can cause illness or death. Although a jar may seal if processed at a lower temperature, it does not mean that the food inside the jar is safe. Processing foods at too low a pressure is a safety issue.

Where can I find up-to-date research tested recipes?

Safe and reliable research tested recipes for canning can be found in our Penn State Extension “Let’s Preserve” series handouts, which can be found at; on the National Center for Home Food Preservation website,; in the book “So Easy to Preserve” from the University of Georgia, and in the “USDA Complete Guide to Home Canning” or other university/Extension publications.

“The Ball Blue Book” also contains research-tested recipes; use one published after 1994.

What could happen if I do not test my gauge and if the gauge is not accurate?

There could be safety and quality issues. If a dial gauge reads higher than the actual pressure, the processing temperature is lower than recommended; this is a safety issue. However, if the gauge registers lower than the actual pressure, the processing temperature is higher than recommended and the food inside the jar may be overcooked and softer in texture than desired. This is not a safety issue but is a quality issue, especially when canning tender fruit.

When I get my dial gauge tested what do the test results mean?

If the dial gauge tests off by less than two pounds, you will need to adjust the pounds (of) pressure you use when processing the foods. If a gauge tests off by more than two pounds, the dial gauge should be replaced. Also, a gauge should be replaced if it is cracked or the glass cover is missing. At the same time that your dial gauge is being tested, the condition of the gasket, pressure plug, and safety lock will be examined.

If I do need to replace a part on my pressure canner what do I need to have to make sure I purchase the correct part?

Before shopping for replacement parts, make certain that you have the model number of your canner. The model number will be found on the bottom of the canner, on the handle, or on the lid. Replacement parts may not be available for very old canners.

Question: Where can I get my pressure canner gauge tested?

Penn State Extension will be testing dial gauges this summer. Due to COVID-19 risks, clean gauges or lids can be dropped off at a Good’s Store location, listed below, for testing. The clean gauge or lid will be tested, and customers will pick the gauge or lid up on a separate date. Testing this year will be completed over a two-week period in June.

Dropoffs and testing will be completed, at no cost, as follows:

• Drop off June 14-16 to Good’s Stores in Schaefferstown or Quarryville. Pick up on or after June 18.

• Drop off June 14-17 to Good’s Stores in East Earl or Ephrata. Pick up on or after June 19.

• Drop off June 21-23 to Good’s Stores in Schaefferstown or Quarryville. Pick up on or after June 25.

• Drop off June 21-24 to Good’s Stores in East Earl or Ephrata. Pick up on or after June 26.

If you miss these test dates, you may call the Lancaster County Penn State Extension office at 717-394-6851 to speak with Stacy Reed to schedule to have your gauge tested at a time convenient for the both of you.

Have a safe and bountiful home food preservation season.

Stacy Reed is an educator with Penn State Extension in Lancaster, specializing in food safety and nutrition.