- 1 Pressure Canning Procedures
- 1.1 1. Check the pressure required
- 1.2 2. Check the processing times required
- 1.3 4. Load the jars
- 1.4 5. Go ahead and vent
- 1.5 6. Bring the machine up to pressure
- 1.6 7. Adjust the heat
- 1.7 8. Maintain the right pressure — not under and not over
- 1.8 9. Processing time is over!
- 1.9 10. Let the canner cool on its own, with no monkey business from you
- 1.10 11. That means, absolutely no forced cooling….
- 1.11 11. How do you know you’re back to Zero pressure?
- 1.12 12. Now that we’re at Zero pressure, how long do you wait before removing the canner lid?
- 1.13 13. Removing the lid
- 1.14 14. Remove the jars
- 1.15 15. Finish the jars
- 2 Big Debate: Move the pressure canner or not when processing is finished and you have turned off the heat?
- 3 Further reading
Pressure Canning Procedures
Here’s a step-by-step guide to how to use a pressure canner.
If you’re looking for information on the “why” — as in, what’s the theory and the reasons behind all these steps, see our page on Pressure Canning Principles. Understanding why can make you better at the how.
But let’s get started with the actual practice.
1. Check the pressure required
Before you start a recipe or a set of directions, look at the pressure that it requires. Make adjustments in your head based on your altitude because “… altitude increases ….[the] pressure required for pressure canning.” 1
Here is a chart of Pressure Canner Altitude Adjustments.
2. Check the processing times required
“Always double and triple check your processing times, making sure you’re using the right time for your packing method and jar size.” 2
Make sure that you will have enough free time to be around for all the time that the processing will take! Don’t forget to allow for about 30 to 40 total minutes of cooling time after the processing time.
3. Check how much water your canner needs
For the modern Presto 16 and 23 US quart canners, it is 3 litres (US quarts.) Other makes and models and sizes will be different.
And don’t forget to add a few tablespoons or squirts of vinegar to the water so that your jars and canner stay sparkling clean!
4. Load the jars
- Put the jars in upright. (Don’t be tempted to try to cheat and lay the jars on their sides — if you do, instead of expelling air, the jars may expel contents!);
- Don’t have the water boiling when you put the jars in;
- For hot pack, have your water simmering already (around 80 C / 180 F if you have a candy thermometer);
- For raw pack, have the water starting to steam but not simmering, around 60 C (140 F). This lower temperature helps avoid heat shock to the somewhat colder jars.
(Note that the temperature of the water in the pot at this stage has nothing to do with food safety: it’s about avoiding thermal shock that could crack the jars.)
5. Go ahead and vent
Have a good vent; you deserve it!
- Lock and load — put the lid on and lock it down;
- If you have a modern canner, leave the weighted gauge off at first. In an older canner, have the petcock open;
- Crank up the heat and get the water boiling in the canner;
- Be patient, let it keep boiling and wait about 10 to 20 minutes depending on your canner size until you start to see steam;
- Once you see steam coming out in a good steady stream either from a vent pipe or air vent/ cover lock, set a timer and allow that steam to vent steadily for 10 minutes.
Should the seal ever reveal itself to be faulty during the venting period (which is usually when it does), turn off the heat, remove the lid when it’s safe to do so heat-wise being careful of sudden steam, replace the seal if you have a spare to hand (this is a good reason to), and start all over again, including the full 10 minute vent.
NOTE: The venting time required can be longer if you are pressure canning fish or seafood. Follow those venting procedures from your tested recipe.
6. Bring the machine up to pressure
With the venting done, close the vent pipe or pet cock to start trapping the steam inside and start building pressure towards the required amount for your altitude.
You can have the stove burner up high to help the canner get up to pressure faster.
Some people argue, though, that it’s best to try to rise up to pressure gradually rather than superfast, because they feel that trying to rise up to pressure really fast can result in some liquid loss and seal failures with the jars. This may be particularly important when using Tattler lids to prevent liquid loss.
Presto in fact advises to lower the heat a bit in advance before reaching pressure. They write,
Helpful Hint: To more easily maintain pressure, it may be beneficial to reduce the heat when the dial gauge registers 1½ to 2 pounds less than the desired pressure. However, do not begin the processing countdown until correct pressure is reached.”3
You only start timing the actual processing time when the actual required pressure is achieved.
7. Adjust the heat
Once the canner hits pressure, lower the heat down to the bare minimum required to maintain pressure without going under the required pressure. “Regulate the heat under the canner to maintain a steady pressure at or slightly above the correct gauge pressure.” 4
8. Maintain the right pressure — not under and not over
You don’t want run at underpressure but nor do you want overpressure, and nor do you want up and down pressure, even if the up and down stays above the safety range for your product.
“Quick and large pressure variations during processing may cause jars to lose liquid.” 5
Overpressure won’t help you, it will hinder you:
- It won’t help provide extra safety. If you are following USDA guidelines there are already wide safety margins built-in up the wazoo;
- It could affect food quality and seal of jar;
- You run the risk of running out of water, and damaging the canner, and ruining your load of food.
If you are using a weighted canner, you don’t want furious rocking and water spewing out: you want just the gentle rocking appropriate for your canner’s rocker The rocking experience is different by brand:
- With an All American, it is 1 to 4 times a minute.
- With a Mirro, 3 to 4 times a minute.
- With a Presto, it is a constant slow steady rocking — don’t try to get it down to just a few jiggles a minute or you will lose pressure.
“Generally, weighted gauges on Mirro canners should jiggle about two or three times per minute. On Presto canners, the weighted gauge should rock slowly throughout the process.” 6
All American gives this advice for their machines:
When the correct pressure has been reached, the Pressure Regulator Weight will jiggle and sputter. Possibly a few drops of water will trickle from the Pressure Regulator Weight. You now begin counting the processing/cooking time from this moment. Reduce the heat so that the Pressure Regulator Weight will jiggle only about one to four times a minute. Do not permit constant jiggling, for this will cause excessive loss of moisture. The occasional jiggle and the hissing sound indicate that you are maintaining the correct pressure. If the steam escapes in a steady stream after you’ve reduced the heat, nudge the control to set pressure Regulator Weight properly.” 7
If the pressure drops during processing, you must bring it back up to pressure and start the processing timing all over again. Not the preliminary venting time, but the called-for processing time. “The correct gauge pressure must be maintained for the entire processing time. If the pressure drops below the target pressure, reset your timer and process for the entire recommended processing time.” 8
“If, for any reason, the pressure should drop during processing, the processing time must be recounted from the beginning.” 9
“Drop in pressure during processing means the sterilizing value of the process will be decreased == Underprocessing. Foodborne illness (botulism) and/or spoilage could result. If pressure drops below target anytime during the process time, bring the canner back up to pressure and start timing the process over, from the beginning. 10
“To have a product that is safe, the heat treatment must be one long, continuous process at the correct pressure.” 11
9. Processing time is over!
At end of the required processing time, turn off the heat.
If you are able to lift the canner just enough to move it off the still-hot burner without scratching the stove or dislocating your shoulder or throwing your back out, you may do so. See debate about this at the end of this page.
But otherwise, that’s all you can do as far as reducing heat now goes.
Here are some estimated cooling times: “Heavy-walled older canners: 30 min full of pint jars, 45 min full of quarts. Thinner wall, newer canners: 20 to 30 minutes.” 12
10. Let the canner cool on its own, with no monkey business from you
You must let the pressure drop naturally, with the weights and gauges still fully closed, for all kinds of reasons.
This natural pressure drop and cooling is vital for safety. During this cool down time, sterilization that the USDA is counting on is still happening. In a pressure canner, the heat-up and cool-down time is counted as heat penetration / sterilization time so don’t try to rush the cool down. See our page on Pressure Canning Principles.
“When process time is complete, turn off the heat. Allow the pressure to drop naturally to 0. Rushing this step can result in product loss from jars and insufficient processing.” 13
The natural cooling is also vital for quality of your canned product.
“Do not force cool the canner. Forced cooling may result in food spoilage. Cooling the canner with cold running water or opening the vent port before the canner is fully depressurized are types of forced cooling. They will also cause loss of liquid from jars and seal failures. Force cooling may also warp the canner lid.” 14
11. That means, absolutely no forced cooling….
Forced cooling refers to cooling the canner by running cold water over it or opening the vent port before the canner pressure drops to 0 psig. Other methods that are sometimes used to force cool include covering the canner with wet towels, wet sheets or wet pillows or bags of ice or frozen peas, or placing the canner in cold air drafts or in a pile of snow outside the back door.
We’ve all been there at times — desperate for the canner to open so we can get the next load started. But don’t do it.
Forced cooling may result in spoilage. Cooling the canner with cold running water or opening the vent port before the canner is fully depressurized may cause jars to lose liquid and to fail to seal. Forced cooling may also warp the lids of older-model canners, causing steam leaks.” 15
Force cooling is just nasty. It may result in 16 :
- Food spoilage;
- Foodborne illness;
- Loss of liquid from jars;
- Seal failures;
- Warping the canner lid.
11. How do you know you’re back to Zero pressure?
Different canners indicate 0 pressure in different ways; it is often a plug or piece of metal dropping. After you think you know that pressure is at 0, wait a further 2 minutes (that’s just to make totally sure, to totally avoid any depressurization of jars.) “Wait about 1-2 minutes after pressure drops to 0 psig to make sure all pressure is gone. For some canners, check that locks in handles are released.” 17
Canners with vent-lock pistons are normally depressurized when their pistons drop to a normal position. “These canners are depressurized when their vent lock pistons drop to a normal position.” 18 But occasionally there will still be just a bit of pressure in them after that even.
If you are weighted-gauge, do a trial lift of the weight by just a few millimetres. At the first, slightest sound of hissing, drop the weight like a hot potato back down and wait a bit longer.
12. Now that we’re at Zero pressure, how long do you wait before removing the canner lid?
Summary: Now wait ten minutes before removing the canner lid.
That’s what Elizabeth Andress, head of the National Center for Home Food Preservation, says:
“Remove weight or open petcock. Wait 10 min.” 19
Details, if you are curious:
Advice on how long to wait before removing the lid appears to be evolving. Note that none of the varying advice constitutes a safety matter; it’s just procedural opinion.
The advice in the past 10 years or so has been: when you are sure the pressure is dropped, remove weight or open petcock and wait a further 10 minutes before opening the canner.
Note that this matter is not a food safety issue: it’s a quality issue, largely to avoid liquid surging in jars and seals being compromised.
The University of Nebraska-Lincoln says,
“Pressure Canner Wait Time: 10 Minutes: … in 2006, pressure canning directions were updated advising consumers to “Wait 10 minutes, unfasten the lid, and remove it carefully” to be consistent with a major U.S. pressure canner manufacturer’s advice, as well the advice from the major U.S. canning lid manufacturer. (When using a pressure canner: ‘After the canner is completely depressurized, remove the weight from the vent port or open the petcock. Wait 10 minutes; then unfasten the lid and remove it carefully.'” 20
Pacific Northwest Extension Services says,
After the canner has lost pressure, remove the weight from the vent port or open the petcock. Wait 10 minutes, unfasten the lid, and remove it carefully.” 21.
The purpose of this is to let the jars rest; research has shown it helps with sealing success. An extension agent writes,
The 10 minutes lets the jars rest a bit before they are lifted. It also helps protect them from super extreme thermal shock from the temperature difference of the air.” 22
Elizabeth Andress says in more detail:
For Dial Gauge: Watch needle on dial. After it reads 0 psig, carefully remove the (counter) weight. If there are piston locks in the lid or handle, see that they have also opened. Wait 10 minutes, then open lid. Remove jars from canner. 23
Bernardin, in both the Bernardin Guide (2013, page 7) and Ball / Bernardin Complete (2015, page 383), say to only wait 2 minutes after zero pressure to remove the pressure canner lid:
When the pressure has returned to zero, wait 2 additional minutes, then remove the weight from the lid. Unlock and remove lid….”24
In 2013, the Ball company in its 36th Blue Book said, “After the processing period is complete, turn off heat. Allow the canner to cool naturally. Do not remove the weighted gauge or open the petcock until the canner has depressurized and returned to zero pressure. Remove gauge or open petcock. Let canner cool 10 minutes before removing lid. Unlock lid and lift it off the canner base, being careful that steam escapes away from you. Let canner cool 10 minutes before removing jars.” 25
As of 2015, Ball’s advice appears to have changed. Or gotten mixed up. The 2015 37th Blue Book (actually dated 2014, but released spring 2015) advises variously 0, 5, or 10 minutes wait before removing the cover.
Here’s a 0 minute recommendation on page 13 of the 37th Blue Book: “After the canner has depressurized and returned to zero pressure, remove the gauge. Unlock lid and lift it off the canner base so that the steam escapes away from you. Let canner cool 10 minutes before removing jars. ”26
Here’s a 5 minute recommendation on page 98 of the 37th Blue Book: “Turn heat off, cool canner to zero pressure. After 5 minutes, remove lid. Let jars cool 10 minutes.”27
Here’s a 10 minute recommendation on page 118 of the 37th Blue Book: “Remove the weighted gauge after the canner is depressurized — at zero pressure. Let the canner cool 10 minutes before removing the lid…..Allow the jars to remain in the canner for 10 minutes to adjust to the lower room temperature.” 28
Most individual recipes in the 37th 2015 Blue Book call for the 5 minute wait before removing the cover.
HeathlyCanning.com for now still follows the USDA / NCHFP recommendation: when pressure is at absolute 0, remove weight or open pet cock and wait 10 minutes before removing cover.
13. Removing the lid
Even though the pressure is at 0, and you’ve waited a bit longer even, know that the temperature inside the canner will still be extreme.
Wear oven gloves. Just do it. The time you don’t will be when something goes wrong and you wish you had.
With oven gloves on, remove the lid, using the lid as a shield in front of you to direct steam away from your face, because there will surely be a blast of super-heated steam.
Pacific Northwest Extension Services says,
Lift the lid away from you so that the steam does not burn your face.”29
Elizabeth Andress, of the National Center for Home Food Preservation, says
In pressure canning, turn heat off at end of process and let jars cool in canner until pressure is gone. When the canner lid is opened, tilt it so the steam is pushed away from your face. The steam, water and jars in the canner will still be very hot, even bubbling or boiling.” 30
14. Remove the jars
Summary: We’re going to go with Ball and Bernardin and say wait a further 10 minutes after removing the pressure canner lid before removing the jars.
After the lid has been removed, advice about how long to wait before removing the jars ranges from 0 minutes to 10 minutes. Note that none of the varying advice constitutes a safety matter; it’s just procedural opinion.
The USDA and So Easy to Preserve say that once you’ve removed the pressure canner lid, you’re done: remove the jars. So, zero additional waiting time.
Elizabeth Andress, co-author of So Easy to Preserve, says:
Open canner. (Be careful of steam!) Remove jars to padded surface or rack. Cool jars 12 to 24 hours, undisturbed. Check that jars have sealed.” 31
Ball and Bernardin differ from that. They both say to leave the jars in the freshly-uncovered pot for an additional 10 minutes.
Unlock and remove lid…. Let jars sit in the canner for 10 minutes to adjust to the lower temperature in the room.” (( Ball / Bernardin Complete 2015, page 383 ))
The Ball Blue Book 37th Edition (2014), however inconsistent it is about wait time before removing the lid, is consistent in saying that once the lid is off, wait a further 10 minutes before removing the jars.
At any event, the jars need to be removed shortly after the lid is off. Do not leave them in the canner for a while or over night, with or without the lid on, or you may develop flat sour and ruin all your work.
Pacific Northwest Extension Services says,
Remove jars with a lifter, and place them on a towel or cooling rack. Allow the jars to cool undisturbed at room temperature for 12 to 24 hours.” 32
Set the jars on a towel or wire rack; never directly on a countertop, or the jars may encounter thermal shock and crack.
When canner is cool enough to safely lift, tip out the canning water into the sink. Rinse out the canner, and the lid, being careful not to get any gauge wet. Set aside to dry.
15. Finish the jars
Let jars cool for 12 to 24 hours [Ed: uncovered with towels etc, and not near open windows with icy drafts.] Remove screw-on rings (or clamps if you used Weck or Vacola.) If any rings are stuck on the jars, stand jars upside down in enough warm water to cover the rings for a few minutes, then remove rings. Gently and cautiously lift each jar up a bit by the actual lid. If it stays on, you have a seal. Wipe the jar down. Set aside to dry. Then label with food product, month and year, and batch # if appropriate. Store. Let jar rings air dry then store separately.
If any jars didn’t seal, put in fridge and use up within a few days, or freeze if appropriate for that food product, or reprocess (after wiping rims and with a fresh lid) if you have another similarly timed batch coming up very soon.
Big Debate: Move the pressure canner or not when processing is finished and you have turned off the heat?
The experts disagree about whether you should move the pressure canner off the burner when the processing time is finished. HealthyCanning.com presents the conflicting advice to let you decide.
What are the University Extension Agents saying?
The University of California says,
It is best not to move the canner while it is cooling. If you do move the canner, do not place it on a cold surface.” 33
Clemson University says,
When the processing time is up, turn off the burner. (If you are using a coal or wood stove, remove the canner from heat.)” 34
The University of Alaska says,
At the end of the processing time, slide the canner away from the heat so it can cool.” 35
Pacific Northwest Extension Services says,
When the timed process is over, turn off the heat, remove the canner from the heat if possible…” 36
What do the canner manufacturers and the USDA say?
Mirro is silent on the topic; page 35 of the manual just says, “turn off heat. Let canner cool.” The All-American manual, page 9, says, “Turn off the heat… Do not move the pressure cooker until the pressure is completely reduced.”
Here’s what Presto advises for their pressure canners, and what the USDA in fact advises for all pressure canners — they both seem to want it off the burner when processing time is up:
At the end of processing time, turn burner to ‘off’ and remove canner from heat source. Note: Lift pressure canner to remove it from burner. Sliding cookware can leave scratches on stovetops.” 37
The USDA says,
When the timed process is completed, turn off the heat, remove the canner from heat if possible, and let the canner depressurize.” 38
Note the USDA says “if possible.” It could be that’s your out for not giving yourself a week in hospital with a hernia, if the canner is just too heavy.
So Easy to Preserve has perhaps the most practical, detailed advice of all,
When the timed process is completed, turn off the heat, remove the canner from the heat (electric burner) if possible, and let the canner cool down naturally. If the canner is too heavy or you are using a gas burner, simply turn off the heat.” (( Andress, Elizabeth L. and Judy A. Harrison. So Easy to Preserve. University of Georgia Cooperative Extension. Bulletin 989. Sixth Edition. 2014. Page 31. ))
But whatever you do, whether you move it or not, note that the weights, vents, petcocks, etc, are all to be still fully in place at this point.
Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” Webinar. 27 February 2013.
Andress, Elizabeth. Preserving Food: Using Pressure Canners. University of Georgia Extension Service. June 2011.
Swanson, Marilyn A. Using and caring for your pressure canner. Pacific Northwest Extension Publication. PNW 421. July 2010 revision.
University of Minnesota: online pressure canning tutorial.
Pressure Canning Step-By-Step Pictorial. University of Nebraska video. 2009. (note that Ball has since said that heating lids is no longer necessary.)
Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” Webinar. 27 February 2013. Accessed January 2015. ↩
Pemmons, Skip (2014-09-14). Next Generation Home Canning: Contemporary and Fun Recipes for Beginners . Kindle Edition. ↩
Presto Pressure Canner and Cooker, 23 quart model, #72-719F. 2014. p 6. ↩
Marilyn A. Swanson. Using and caring for your pressure canner. Pacific Northwest Extension. July 2013. PNW .421. Accessed March 2015 at http://www.cals.uidaho.edu/edcomm/pdf/PNW/PNW0421.pdf ↩
Cooking & Canning with the All-American Pressure Cooker / Canner Manual. 2008. Accessed March 2015. Page 19. ↩
Dinstel, Roxie Rodgers. Food Preservation. Back to Basics, Lesson 1. University of Alaska Fairbanks Cooperative Extension Service. FNH-00562A. Revised March 2013. ↩
National Center for Home Food Preservation Self Study Course. Module 4. Canning Low Acid Foods: Problems in Pressure Processing. Accessed March 2015. ↩
National Center for Home Food Preservation Self Study Course. Module 2. General Canning: Pressure Canner Processing. Accessed March 2015. ↩
National Center for Home Food Preservation Self Study Course. Module 4. Canning Low Acid Foods: Dial Gauge Canners. Accessed March 2015. )
The Ball company says that if the pressure drops too quickly, your metal sealing lids will buckle:
If you are pressure canning, and you bring the pressure back down to zero too quickly, that can cause the lids to buckle, too much pressure, the pressure change, the lids are actually designed to buckle when the pressure gets too great versus the glass breaking… so that’s a good thing, you want it to buckle, because now you know that there is something wrong in your process, and when your lids do buckle, you actually have to reprocess, you have two hours to reprocess.” (( Jessica Piper. Video: Canning Lids 101. (20:20) Accessed March 2015. ↩
National Center for Home Food Preservation Self Study Course. Module 4. Canning Low Acid Foods: Problems in Pressure Processing . Accessed March 2015. ↩
Ball / Bernardin Complete 2015, page 383 ↩
Ball Blue Book Guide to Preserving. Daleville, Indiana: Hearthmark LLC. Edition 36. 2013. Page 12. ↩
Ball Blue Book. Muncie, Indiana: Healthmark LLC / Jarden Home Brands. Edition 37. 2014. Page 13. ↩
Ibid., Chopped Meat Recipe, Page 98. ↩
Ibid., Page 118. ↩
Harris, Linda J. Safe Methods of Canning Vegetables. University of California, Division of Agriculture and Natural Resources. ANR Publication 8072. 2002. Page 4. ↩
United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-22. ↩