Pressure Canning 101

Just the thought of firing up this potentially explosive stove-top appliance sends many of us running for cover! Whistling petcocks, clouds of scalding steam, and slippery jars all compound to create nightmarish visions of 3rd degree burns and spaghetti sauce dripping from the ceiling. It’s true, pressure canners are potentially dangerous, but they are perfectly safe when the manufacturer’s directions are carefully followed. Never use a pressure canner that does not have an accompanying instruction manual.

Heat is the weapon the home canner wields in the battle against decay and toxins. High acid foods like most fruits and pickles can be safely processed at 212 F–the boiling point of water. Low acid foods which include vegetables, meats, and fish must be processed at 240 F to ensure that harmful, heat tolerant bacteria are destroyed. Thus, these foods require the use of a pressure canner which is capable of reaching and sustaining temperatures above the boiling point. So, if your tomato crop is huge or you’ve recently caught a giant salmon it’s time to make peace with and get to know your friendly stove top pressure canner.

Read through and follow these simple steps for pressure-free pressure canning:

[Editor’s note: read through the entire manual before using the pressure canner.  Check all parts to make sure they are in working order.]

• Place the pressure canner, containing its wire basket, on a cold stovetop element.

• Refer to your manual to determine how much water to add to the canner to begin. [Editor’s note: heat the water according to your manual’s directions]

• Place filled jars, tops screwed on, in the wire basket.

• Tightly secure the lid on the pressure canner according to instructions.

• Check the petcock valves with a toothpick or fine wire to determine that they are clear.

• Turn on the heat beneath the canner and watch for steam. Once steam begins to flow from the valve, begin timing and maintain a steady flow for 10 minutes. This exhausting or venting of the canner is air leaving the jars and canner. If the canner isn’t properly exhausted, the air will cause the reading on the gauge to be inaccurate, and your canning temperatures may be too low to be safe.

• After the canner has exhausted for 10 minutes, close the vent or place the weight control over the steam valve.

• Watch for the pressure gauge to reach the correct pressure (this is the time to make altitude adjustments). Then set your timer and begin the designated processing time. Adjust the heat source so the gauge stays at the correct pressure called for in your recipe. Half-pint jars and smaller are processed in the same way as pints.

• When jars have been processed for the correct amount of time, move the pressure canner off the heat and let it cool completely. Caution: the canner will be very hot; protect yourself with oven mitts and pot holders. [Editor’s note: it is probably a better idea to turn off the heat and let the canner cool on the burner.  Moving a heavy pressure canner can damage the jars inside]

• The steam and heat inside even a “cool” canner can be dangerous. Wait until the pressure gauge has gone down to zero or until you can no longer see steam coming from the vent. On average it takes 45-60 minutes for the pressure to go all the way down.

• Open the petcock slowly or remove the weighted gauge (remember, it’s hot!). Unlock the canner lid and slide it across the top of the canner toward you, letting any remaining hot steam escape from the far side of the canner. Allow the canner to sit without its lid for 10 minutes before removing the jars to a countertop that has been insulated with dishtowels or newspaper to avoid breakage due to a temperature contrast between the hot jars and a cool surface.

[Editor’s Note:  You may also want to read Using Pressure Canners from the National Center for Home Food Preservation site.]

CAA Contributor Lorene Edwards Forkner is a freelance writer, garden designer, and food enthusiast in the Pacific Northwest. She is the co-author of Canning & Preserving Your Own Harvest. Both books are based on material original to The Encyclopedia of Country Living, by Carla Emery.

Comments (2)

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    Great resource for beginners!

    Lorene - I appreciate your Pressure Canning tutorial but there are a few changes I would add to the article that I think that a home user will need to know.

    1st they should heat the water in the canner before they put it in their jars. This allows the canner to get to temperature faster once they close the lid so that the jars are not cooling down in the water while the canner heats up internally.

    2nd they should check the petcock valve and all of the equipment before they start. They can check to see that the hole is clear by looking through and seeing light. They should also check to make sure the gasket is in properly before they put the lid on the machine.

    3rd the exhausting of the canner is not the air leaving the jars. The venting of the canner is to make sure that the internal temperature and steam produced will account for an accurate read on the gauge.

    4th Never move the canner off the heat. If you have ever lifter a double stacked 23 qt pressure canner it is way too heavy and the damage you could do to the jars inside could be a disaster. You could have to siphon problems, cracked jars, not to mention burns if you are not careful. If you are cooking on an electrical element that takes time to cool down you will have to do some adjusting of time but never move a full canner once it’s in place.

    5th You may not see steam and some canner will have a “lid lock” which once a dial gauge returns to zero and the lid lock button goes down you can open the canner safely. The same goes for the weight gauge. Do not knock the gauge off just to see if there is any steam left. It will cause a change in pressure and you will have a loss of liquid in your jars.

    6th The other reason you will want to wait to take the jars out of the canner is there is a change in pressure from the canner to the counter. If you take them out right away it’s like a scuba diver if you don’t adjust for the change in pressure slowly you will have liquid spewing out the sides of the jar. Taking the 10 minutes allows the internal pressure of the canner to return to the external pressure.

    I know now from experience that canners who want to do low acid foods want more detail to be confident. Thank you for the post and more so thank you for allowing me to make additional comments.