Sometimes concerns are raised about the heat sources for pressure canners. The concerns can be summed up as follows:
Bottoms of canners
Pressure canners with concave bottoms (Mirro models) can’t be used on flat stop stoves because the heat won’t transfer effectively; you need a canner with a flat bottom resting on the flat stove top. “Mirro pressure cooker/canners are not designed to be used on a flat top (glass or ceramic) range because they have concave bottoms. On a flat top range, a large area of the bottom will be out of contact with the heat source, preventing the transfer of heat and the buildup of pressure.” [1] Marilyn A. Swanson. Using and caring for your pressure canner. Pacific Northwest Extension. July 2013. PNW .421. Accessed March 2015 at https://www.cals.uidaho.edu/edcomm/pdf/PNW/PNW0421.pdf
Heat source too high
Presto and Mirro canners can’t be used on heat sources over 12,000 BTUs because heat above that will damage the canner by warping the bottom.
Safety insert that comes packaged with Presto pressure canners
A safety insert that comes in the box with a Presto canner says not to use the canner with any outdoor burner. Wording in the manual, however, owing perhaps to some missing commas in the language, has caused some confusion: is the warning against any gas burner outdoors, or, just those with over 12,000 BTU’s? Many people interpret the precaution to be only if you can’t keep the outdoor burner under 12,000 BTU’s.
“Caution: Do not use pressure canner on an outdoor LP gas burner or gas range over 12,000 BTU’s. Doing so may result in damage to the pressure canner and/or property damage and personal injury.” [2] Presto 01781 23 Quart Model Manual. Form 72-719E. Accessed March 2015 at https://www.gopresto.com/downloads/instructions/01781.pdf
“Some stovetops or heat sources may be inappropriate for pressure canning. Both Presto and Mirro pressure cooker/canners are not designed to be used on an outdoor liquid propane burner or on a gas range over 12,000 BTUs because excessive heat will warp the canner bottom.” [3] Marilyn A. Swanson. Using and caring for your pressure canner. Pacific Northwest Extension. July 2013. PNW .421. Accessed March 2015 at https://www.cals.uidaho.edu/edcomm/pdf/PNW/PNW0421.pdf
Most everyone agrees to definitely avoid any “turkey fryer” propane heaters because of the high heat required to boil the oil to fry the turkey would damage many canners.
Some people say, however, that there are some safe outdoor heat sources — ones with adjustable temperature controls such as the Camp Chef line. “Only Camp Chef brand 2 burner stove on low is the only safe one we know of.” [4] Linda Lou. Extension Assistant Agent. 24 July 2013. Accessed March 2015 at https://forums.gardenweb.com/discussions/1951629/mirro-canning-help#7027693
Outdoors
Mirro says not to use their pressure canners outdoors at all: “Do not use the cooker outdoors.” [5] Mirro Pressure Cooker & Canners Instructions Manual & Recipe Book. Year Unknown. Page 2. Accessed March 2015 at https://www.hippressurecooking.com/mirro-pressure-cooker-and-canner-instruction-manual/
Flat / glass stove tops
As of spring 2015, only Presto and Fagor appear to make pressure canners that are safe to use on glass stove tops. (The only size Fagor offers is a 10 quart size, which will hold only 4 x 1 litre / US quart jars at a time.)
Even though it may be difficult to find information online about whether Mirro is glass-top safe or top, it actually does say right on the box at the store, “NOT compatible with ceramic or glass cooktops.” The concern with Mirro and glass stove tops seems to be the way the heat would be distributed on the glass.
The concern with All-American and glass stove tops seems to be the way the heat would be distributed on the glass, plus the weight.
Presto certifies its two contemporary canners, the 16 and 23 quart, for flat stove tops. Note that this doesn’t necessarily mean the reverse, however: that all flat-top stove makers certify their stove tops for canning. You have to check your stove’s manual or check with the manufacturer. The usual concerns are heat build-up, and weight.
Some people express concern about smooth top burners maintaining an even heat. “Many of these cooktops have automatic cut-offs on their burners when heat gets excessive. If that option is built in, and the burner under a canner shuts off during the process time, then the product will be underprocessed and cannot be salvaged as a canned food. The process time must be continuous at the intended temperature…” [6] Burning issue: Canning on smooth cooktops. National Center for Home Food Preservation. June 2011. https://nchfp.uga.edu/publications/nchfp/factsheets/smoothtops.html
Others point out that the emergency cut off of power to a burner being described above is very different from a burner cycling in normal operation to regulate itself to maintain a desired temperature. The pressure is the temperature, and as long as your weight or gauge is indicating the correct pressure, then you have the correct temperature inside the canner. The Maytag Gemini stove manual says, “The surface cooking area will glow red when an element is on. Some parts of the surface cooking area may not glow red when an element is on. This is normal operation. It may cycle on and off to maintain the selected heat level.” [7] Smooth Top Double Oven Range Manual. W10345638A 2010. Page 7.
The Maytag Gemini stove manual also gives this advice for its glass stove top: “Do not place canner on 2 surface cooking areas, elements or surface burners at the same time.” (i.e. don’t try to “bridge” between two burners.) ” [8]Ibid, page 8 And, “When canning for long periods, alternate the use of surface cooking areas, elements or surface burners between batches. This allows time for the most recently used areas to cool.” [9]Ibid, page 8
Pressure Canners on Induction Burners
If you have an induction stove top (note: not just flat glass stove top, but induction in addition to that), then you can’t use aluminum on it: it just won’t heat up, the heat won’t transfer to the aluminum. But you can get a “converter plate” you slide in between the induction burner and the aluminum pot that does the heat transfer.
Mirro, and All American make their pressure canners out of aluminum and therefore would require such a converter plate to work on an induction burner (as of 2020).
In 2019, Presto released a pressure canner that will work on induction stove tops. Any Presto models other than their induction compatible model requires a converter plate.
Further reading
Alternatives to Smooth Top Ranges. Accessed March 2015 at https://www.clemson.edu/extension/food_nutrition/canning/tips/19smooth_top_alternatives.html
Burning Issue: Canning on Portable Burners. Can I can on portable gas or electric burners? National Center for Home Food Preservation . 7 November 2014 https://nchfp.uga.edu/publications/nchfp/factsheets/canning_portable.html
Burning issue: Canning on smooth cooktops. National Center for Home Food Preservation. June 2011. https://nchfp.uga.edu/publications/nchfp/factsheets/smoothtops.html
References
CHRISTINE Kuba
We are canning at a church with an All American canner. Can we use it on the commercial stove?