Why do I need to Use a Canner?
and How to Choose a Canner

People occasionally ask, "why use a water bath method or a pressure canner. My grandmother used and she never got ill!" That may be true, just as there are occasionally smokers who live to 100 or people who cross the street without looking and don't get hit by a car.  But no rational person would recommend these either...

The US Department of Agriculture and many major universities (Clemson, University of Georgia, University of Illinois, University of Wisconsin, University of Minnesota, to name a few; click here for links to the references, at the bottom of this page) l have each extensively studied food safety and home canning.  To summarize their findings; all of them state that if you are canning at home, including making jams and jellies, you must use a water bath or pressure canner, if you want to avoid food poisoning.  By food poisoning they are referring to varieties of bacteria, such as botulism, that grow in a sealed environment.  Without hyperbole, death is one of the outcomes of such poisoning.  See this page for detailed information about botulism food poisoning.

Some recipes, particularly old family recipes and many floating around on the internet don't call for processing.  The food is cooked in an ordinary pot or kettle, then packed into hot jars and sealed without processing (this is called the "open kettle method").. The temperatures obtained in open kettle canning are not high enough to destroy all spoilage and food poisoning organisms that may be in the food. Also, microorganisms can enter the food when it is transferred from the kettle to jar and cause spoilage. These are obsolete and may be dangerous.  According to the USDA;

"Canning recipes prior to 1990 should not be used. Many old recipes do not include instructions for processing foods. The foods are canned by the open kettle method, sealed and stored. This method for canning, the open kettle method, is not recommended for it presents a serious food safety hazard. All high acid foods should be processed in a water bath canner and all low acid foods in a pressure canner. "

Grandma says I don't need to use a water bath, just fill and seal the jars! Explain it to me, again, slowly...

Were he alive, Louis Pasteur would tell you that at the time you sealed the jars, the temperature of the contents had already dropped way below 212 F.  Meanwhile, the jars were exposed to the air (temp 70f to 90 F) which is not a sterile environment and does contain floating spores of Clostidium Botulism and other harmful bacteria. Therefore, the sealed jars now contain small amounts of live lethal bacteria.

Also, microorganisms can enter the food when it is transferred from the kettle to jar and cause spoilage. (Surprisingly to some, the air in your kitchen is not sterile).

Over time, those spores would grow. Typically, some bacteria grow that consume remaining oxygen and create an environment ideal for Clostidium Botulism to then grow as a secondary bloom. How fast and to what extent, is subject to many variables, but how many of us want to play Russian roulette with our health and food?

Water bath processing would kill the vast majority of those spores, creating a sealed sterile environment. Does this help explain it in terms that even Grandma would grasp? :)

OK, I need a canner?  Why types are there?

Equipment for heat-processing home-canned food is of two main types--boiling-water canners and pressure canners. There are many other types which are NOT recommended by the authorities (see this page for more about obsolete and unsafe canning methods)

Most are designed to hold seven quart jars or eight to nine pints. Small pressure canners hold four quart jars; some large pressure canners hold 18 pint jars in two layers, but hold only seven quart jars. Pressure saucepans with smaller volume capacities are not recommended for use in canning. Small capacity pressure canners are treated in a similar manner as standard larger canners, and should be vented using the typical venting procedures.

Low-acid foods must be processed in a pressure canner to be free of botulism risksThis is because botulism-producing bacteria produce spores that can survive boiling water temperatures, but are destroyed using a pressure canner with the appropriate time and pressure, which reaches temperatures between 240 and 250 degrees F.  Low-acid foods include meats, dairy, sea food, poultry, all vegetables (except tomatoes) and many fruits (notably figs).  Be sure to see this page for a detailed list of the  Acid content of common fruits and vegetables.

Higher acid foods (and those which have been acidified and tested) that may be safely canned in a boiling water bath canner include jams, jellies, pickles, applesauce, apple butter, peaches, peach butter, pears, pear butter, spaghetti sauce without meat, tomatoes, ketchup and tomatoes.

Temperatures and Food Safety

Temperatures for Food Preservation

Temperature(s) Water Bath Home Pressure Canner Effect
Above 250F
(under pressure)
Can't do it Can't do it Canning temperatures for very low acid or non acidic vegetables,  dairy, oils, pesto, pumpkin puree, pumpkin butter, etc.  These can not be safely canned at home, and require the higher temperatures of commercial equipment.
240 to 250F
(under pressure)
Can't do it OK Canning temperatures for low acid vegetables (like green beans, corn), meat, and poultry in a pressure canner. You can also can borderline and high acid foods like tomato products.
(full rolling boil)
OK OK Temperature water boils at sea level. Canning temperature for acid fruits, tomatoes (with added lemon juice), pickles, and jellied products in a boiling-water canner.
180 to 212F
(simmering boil)
OK OK Canning temperatures are used to destroy many common bacteria, yeasts, and molds in acid foods. Time required to kill these decreases as temperatures increase.
140 to 165F     Warming temperatures prevent active growth, but may allow survival of some microorganisms.
40 to 140F     DANGER ZONE. Temperatures between 40F - 140F allow rapid growth of bacteria, yeast, and molds.
95F     Maximum storage temperature for canned foods.
50 to 70F     Best storage temperatures for canned and dried foods.
32F     Temperature at which water freezes.
32 to 40F     Cold temperatures permit slow growth of some bacteria, yeasts, and molds.
-10 to 32F     Freezing temperatures stop growth of microorganisms, but may allow some to survive.
0 to -10F     Best storage temperatures for frozen foods.


Which Type of Canner Should I Get

There are advantages and disadvantages of Pressure and Boiling Water Bath Canners.  Which is best for you depends upon what you want to can and your budget.

Water bath canners are faster for higher acid foods

Although pressure canners may also be used for processing higher acid foods, boiling-water canners are recommended for this purpose because they are faster. A pressure canner would require from 55 to 100 minutes to process a load of jars; while the total time for processing most acid foods in boiling water varies from 25 to 60 minutes. A boiling-water canner loaded with filled jars requires about 20 to 30 minutes of heating before its water begins to boil.

A loaded pressure canner requires about

  • 12 to 15 minutes of heating before it begins to vent;
  • another 10 minutes to vent the canner;
  • another 5 minutes to pressurize the canner;
  • another 8 to 10 minutes to process the acid food; and, finally,
  • another 20 to 60 minutes to cool the canner before removing jars.

But Water Bath Canners cannot be used for meats, dairy, sea food, poultry, vegetables and many fruits.

And the food quality and storage time is better with a pressure canner.  Because they get hotter (240F vs 180F-212F) pressure canners result in a better flavor and the ability for to store for a longer time.

A pressure canner can be used as a boiling water bath canner, just remove the gauge and weight.  That way you have 2 canners in one! 

Conclusion: Pressure canners cost more to buy, but ultimately, you can "can" more foods in them, store the foods longer, and use the same canner as a pressure canner or without sealing the lid, as a boiling water bath canner. 

See this page for a selection of pressure canners at excellent prices, and this link for boiling water bath canners

You can also find free information about canners from the USDA in this PDF file (it will take a while to load!) about selecting and using canners here!

Related Questions and Answers

Q. I have never been able to get a straight answer about whether adding lemon juice or vinegar is necessary if canning salsa in a pressure canner. It would seem to me that you would not need to add the vinegar or lemon juice because you would be bringing up the temperature and maintaining it at high points that would kill off any botulism spores. This would seem to me to be similar to what you do when you safely can your own tuna in a pressure cooker. Can you please provide an answer to this question?

A. Yes, it is necessary! It's more complicated than that!! No process, of any kind, kills ALL spores, so part of the equation is; to what extent is the population of spores diminished, and what will be the replication rate of those that survive? Pressure canning, using high temperatures destroys more spores than water bath canning, and commercial conning equipment destroys a far, far greater percentage of the resident spores than any home method. The addition of acid inhibits the remaining spores growth, keeping the levels of bacteria (which are always present) to a level that is effectively, undetectable and not a threat.  Of course, if you store ANY canned food (home or commercial) long enough, it WILL spoil!  That's why they're stamped with expiration dates!

See this page for more Answers to Common Questions About Home Canning, Freezing and Making Jams!

Who Invented the Canning Jar?  Does Ball still make jars? - See:

A Brief History of the Home Canning Jar: From Mason to Kerr to Ball and More

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  1. Iowa State University - Answer Line
  2. University of Tennessee Agricultural Extension Service - Methods of Canning (PDF)
  3. The "Complete Guide to Home Canning," Agriculture Information Bulletin No. 539, USDA (Revised 1994).


Free Resources About Storing

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Canning books

Canning & Preserving for Dummies
by Karen Ward
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The Ball Blue Book of Preserving

This is THE book on canning!  My grandmother used this book when I was a child.  It tells you in simple instructions how to can almost anything; complete with recipes for jam, jellies, pickles, sauces, canning vegetables, meats, etc.  If it can be canned, this book likely tells you how! Click on the link below for more information and / or to buy (no obligation to buy)

Price £8.95  

Home Canning Kits

This is the same type of  standard canner that my grandmother used to make everything from applesauce to jams and jellies to tomato and spaghetti sauce. This complete kit includes everything you need and lasts for years: the canner, jar rack, jar grabber tongs, lid lifting wand, a plastic funnel, labels, bubble freer, and the bible of canning, the Ball Blue Book. It's much cheaper than buying the items separately. You'll never need anything else except jars and lids (and the jars are reusable). To see more canners, of different styles, makes and prices, click here!

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