- 1 Summary
- 2 What is steam canning?
- 3 Is steam canning authorized?
- 4 What is a steam canner?
- 5 What are the time and energy savings with steam canning?
- 6 What is the downside of steam canning versus water-bath processing?
- 7 What heat surfaces can steam canners be used on?
- 8 What can a steam canner be used for?
- 9 Is there a time limit for how long I can steam can process something?
- 10 What jar sizes can be used?
- 11 What are the usage guidelines for steam canning?
- 12 Altitude adjustments for steam canning
- 13 Monitoring the temperature for steam canning
- 14 Doesn’t steam get hotter than water?
- 15 Can you double-deck when steam canning?
- 16 Steam canning processing steps
- 17 The history of steam canning
- 18 Further Reading
- 19 Shopping
Steam-canning is approved as an equivalent to water-bath processing under the following provisos:
- It is used with tested high-acid recipes for water-bath processing from reputable sources;
- You process for the same times as called for water-bathing;
- For any processing times over 45 minutes, you can’t steam-can and have to switch back to water-bathing instead.
High-acid foods are items such as jams, jellies, most fruits, pickles, relishes, chutneys, salsas, and tomato products with added acid.
Note: much of the background safety theory behind water-bath canning applies to steam canning. See particularly: “The reason why water-bath canning is done.” All those reasons apply to steam canning.
For a review of some actual models, see: Victorio Steam Canners.
What is steam canning?
Steam canning is a method in home canning in which filled jars are processed in an enclosed pot using the heat of steam to do the processing.
The pure steam environment gets to 100 C (212 F), thus having the same sterilizing heat as boiling water.
In the past, it’s also been referred to as “atmospheric steam canning” in order to clarify that it’s happening at a normal atmosphere (pressure), as opposed to under induced, artificial pressure (e.g. pressure canning.)
Compared to water bath canning, steam canning saves both time and energy costs, and your water bill.
Respected home canning author Linda Ziedrich writes:
Steam canners save water, energy, and time, and they don’t boil over.” 1
Steam canning is now “authorized” as of June 2015. See: Using an Atmospheric Steam Canner by Barb Ingham at the University of Wisconsin.
From about the 1960s to 2015, steam canning was recommended against by the canning authorities because comprehensive research wasn’t in place for them to be able to confidently say “yes, it’s 110% safe.” (Which is the kind of level of assurance they need in their jobs, understandably.)
The University of Wisconsin Extension received a grant around 2011 to research steam canning under Barb Ingham. In June 2015, they published the results of their research saying that steam canning can be used in place of water bathing when certain guidelines are followed. More about that in a quick moment, but first, what is a steam canner?
What is a steam canner?
A steam canner is a large-capacity pot designed to trap steam in it, and slowly release any excess steam in a controlled way. The first models were of the type with the shallow pot accompanied by a tall cover; in the past few years, large tall pots with flat lid models (called “multi-canners” because they can be used for water-bathing as well) have come on the market. You put your jars in on a rack, along with a bit of water, then put the cover on, then bring the water to a boil in order to produce steam, and then process the jars with the steam trapped inside by the cover.
Elizabeth Andress, project director at the National Center for Home Food Preservation, says:
Atmospheric steam canning actually means that you are surrounding your jars in a steam environment and not in water at all. A steam canner is kind of an upside down boiling water canning situation, where you put a little bit of water in a shallow bottom tray and bring it to a boil but your jars sit on a rack above the boiling water and are surrounded by steam and that’s what we mean by atmospheric steam canning.” 2
Basic steam canners are inexpensive (around 40 bucks at Walmart as of January 2015), and the benefits are appealing: a steam canner “uses less water than conventional water bath canners, which reduces your preheating time significantly.” 3 The time savings of course result in fuel cost savings.
Slightly more expensive models come with a very handy gauge built into the top to assure you that your steam is indeed maintaining the correct processing temperature.
If yours comes with a rack that makes the jars seated on it unstable (some users complain their steam canner came with a wire rack that the jars could not sit steady on), the Presto pressure canner rack fits into many models.
Some of the slightly more-expensive models, labelled as “multi-canners, can in some instances allow an extra jar to be fit in.
What are the time and energy savings with steam canning?
To recap, any high-acid tested recipe that calls for water-bathing can be steam canned in a steam canner instead.
Let’s look at a jar of jam (jams count as high-acid) that calls for 10 minutes of processing time in a water-bath canner vs steam canner:
Water bath times, for comparison:
In water-bath canning, most people optimistically forget just how long your stove burner has to be on high going full blast just to get a pot of water boiling.
- 15 to 20 to 30 minutes to bring to boil (depending on amount of water in pot);
- Add jars;
- 10 minutes to come back to a boil;
- Processing time;
- Then 5 minute cool-down at the end.
But remember, water bath processing times have to be increased as your altitude increases above sea level, anywhere from 5 to 20 extra minutes. So if you live about 300 metres (1000 feet) you have to keep that pot boiling even longer.
10 minutes processing time at sea level can end up being a minimum of 55 minutes. 50 minutes of that is active energy usage time
Steam canning times for comparison:
- 10 minutes to bring to boil (depending on hot your burner);
- Processing time;
- Then 5 minute cool-down at the end.
Remember: you have to increase processing times above 300 metres (1000 feet) just as you do for water-bath processing.
10 minute processing time at sea level can end up being a minimum of 25 minutes. 20 minutes of that is active energy usage time.
You have saved 30 minutes of time. If you have another load to process, that’s hugely important.
What’s more, you have also reduced your cooking fuel bill by 30 minutes. That’s huge, especially because we are talking about a burner being high enough to maintain a vigorous boil. You have saved money, and reduced your carbon footprint.
For the second half of the 1900s, cooking fuel was relatively cheap in North America. That is changing now, though, and fast. A steam canner will pay for itself quickly in fuel saving costs, and in the meantime, you get to enjoy the time savings.
By the way, if you are thinking a pressure canner for your pickles would be even faster, nope.
Reminder: the water-bath and steam canning options are only available for high-acid foods: jams, jellies, most fruits, pickles, relishes, chutneys, salsas, tomato products with added acid, etc.
What is the downside of steam canning versus water-bath processing?
The experts who studied the process at the University of Wisconsin and the National Center for Home Food Preservation identified no downside.
We suppose the only downside is that steam canning does require a pot specially adapted for it, whereas water bathing could be done in any pot that you can jerry rig a bottom rack for.
What heat surfaces can steam canners be used on?
Steam canners are safe on and work with all gas and regular coil electric stoves.
The issue can be with smooth top stoves. Many steam canners have “wavy” bottoms. Any cooking vessel with a “wavy” bottom struggles to work satisfactorily on smooth stove tops because the heat transfer to those bottoms from flat tops is really inefficient. It means it’s going to take you three times longer to hit the desired temperature, three times more energy to maintain that temperature, and, you can’t count on that temperature staying stable, to boot. Consequently, makers of “wavy” bottom canners of any kind are adamant that they are not for smooth tops — they don’t want to assume the risk liabilities.
Smooth top / glass and induction stove tops
To date, the only steam canner that we know of that will work on and is certified for glass top and induction stoves is the Victorio stainless steel multi-use steam canner. (Note: the stainless steel model, not the aluminum model.) It has a flat bottom, which makes it smooth-top stove friendly, and is made of steel, which enables it to work with induction.
No aluminum canner (or pot for that matter) will work on induction burners without the use of an adapter plate. If you are given an aluminum steam canner and have an induction stove, you could debate trying one of those adapter plates.
What can a steam canner be used for?
A steam canner can be used for processing any home canned food product that a water bath canner could be used for.
That is to say, it must be high acid, which means a pH of 4.6 or under (preferably under.)
Low acid foods must be processed in a pressure canner because a steam canner will never, ever get hot enough to kill off enough nasties for low acid foods. (See below: Doesn’t steam get hotter than water.)
Appropriate foods for steam canner processing therefore include jams, chutneys, pickles, relishes, acidified tomatoes, fruits, etc — the same list of candidates that exists for water-bath canning.
Is there a time limit for how long I can steam can process something?
45 minutes is the maximum time limit for which you can steam can process something.
The time limit exists for a pure and simple technical reason: steam canners can’t hold enough water to generate the needed steam for longer than 45 minutes.
So if a recipe’s processing time would require longer than 45 minutes, you are looking at water bath processing instead (or for plain tomato and plain fruit products, you could consider pressure canning instead.)
What jar sizes can be used?
1/4 litre, 1/2 litre and 1 litre ( 1/2 US pint, 1 US pint, 1 US quart.)
You could of course also use the very small 125 ml (1/2 cup) sampler size jelly jars as well.
What are the usage guidelines for steam canning?
Source: Ingham, Barb. Using an Atmospheric Steam Canner. University of Wisconsin Extension Blog Posting. 24 June 2015.
- Only use recipes which have previously been approved by trusted authorities for water-bath canning. Do not use recipes in booklets that come with the steam canners.
- Heat the jars prior to filling. Fill them with hot liquid (if the food isn’t hot already), and don’t let the jars cool much prior to getting the steam canner going.
- Always use the bottom rack that comes with the steam canner to keep the jars away from direct heat at the bottom of the canner.
- Place recommended amount of water in canner, put jars in and cover on, and turn on burner heat.
- Let the steamer heat up and then vent steam until you see a solid, unbroken column of steam that is 15 to 20 cm (6 to 8 inches) tall coming out.
- When you are sure that you are getting that solid column of steam, then start counting your processing time using the same processing time as recommended by your tested water-bath recipe (with time adjusted for altitude, see below).
- Make sure that column of steam is maintained unbroken for the entire processing time required. Never lift the lid off.
- Regulate the heat to maintain that column of steam. Too low a heat and you may lose your steam; too high a heat and the canner could boil dry in 20 minutes.
- If you lose your column of steam for whatever reason, you have to bring it back up to steam and begin processing time counting all over again.
- Wisconsin doesn’t detail how to end the process, so until then consider perhaps doing the same as for water-bath canning: at the end of processing time, turn the burner off, and remove the cover with oven mitts on and being cautious of steam. Let stand 5 minutes undisturbed, then, remove jars from the canner and place away from drafts on a towel or insulated surface and let stand undisturbed for 12 to 24 hours. Then check seals, wash jars, label and store.
- Do not muck with the cool-down process of the jars once they are removed from the canner. Don’t try to slow the cool-down down by covering them with towels, and above all, don’t try to rush the cool down process. A lot of the lethality of the nasties actually occurs during the natural cool-down process.
Altitude adjustments for steam canning
You can use Google maps to find your altitude. You can enter your entire address in: e.g 123 Queen Street, Upper Lower Bottom, Wisconsin, USA.
You need to modify your steam canner processing time for altitude. “Processing time must be modified for elevation as required by a tested recipe….” 4
You increase the processing time required in the exact same 5 minute increments that you do for water-bath processing.
There’s just one small catch: if after altitude adjustments the processing time that would be required is over 45 minutes, then you can’t use a steam canner for that food product in that size jar and need to either:
- see if reduced processing times are given for smaller jar sizes which will work out for you after altitude adjustments; OR
- water-bath your food product instead.
The reason is that steam canners just don’t hold enough water to steam for longer than 45 minutes; it’s a physical limitation.
“Processing time must be limited to 45 minutes or less, including any modification for elevation.” 5
Because 1 litre (US quart) sized jars of plain tomatoes require 45 minutes water-bathing / steam canning at sea level (300 metres / 1000 feet and below), that would mean that those size jars of tomatoes cannot be steam canned above that altitude. You would need to water bath them (and adjust time for altitude), or, pressure can them (and adjust pressure for altitude), OR switch to the smaller 1/2 litre (US pint) jars.
Monitoring the temperature for steam canning
To be completely sure that you are maintaining a 100 degree (212 F) environment inside the canner, Wisconsin says ideally you could try to place a thermometer (presumably a meat thermometer, but they don’t say whether they mean a regular in-oven one, or an instant read one — or for that matter, a candy thermometer) in the vent hole.
Steam canners that are slightly more expensive, but still affordable, come with a temperature gauge in the top that appears to be worth it to assure you that you are always processing at the correct temperature:
Ideally, temperature should be monitored with a thermometer placed in the vent port, but the placement of jars in the canner may make this difficult. Some appliances come with a built-in temperature sensor in the dome lid and these appear to be accurate.” 6
This is the steam gauge at the top of the Victorio brand steam canner:
Many people say that having a gauge does away with the constant worry of second-guessing yourself as to whether your column of steam is high-enough or solid enough.
Doesn’t steam get hotter than water?
The answer is complicated, but basically no, at regular atmospheric pressure, the maximum heat of both steam and boiling water is 100 degrees (212 F).
Steam will feel hotter, and can scald faster and worse, than boiling water, but that’s because the heat energy in it is more readily and quickly transferred to a hand or arm in the wrong place at the wrong time.
Occasionally steam can get briefly hotter than boiling water, such as when a volcano explodes and produces a flash wave of super-heated steam.
To produce steam hotter than boiling water, you need to do it under pressure.
That’s a very simplistic answer leaving out lots of important details but it will do for a quick layman’s explanation. To really dig into the matter, you need to go to forums where physicists or engineers hang out, such as this discussion at the Physics Forums.
Can you double-deck when steam canning?
Yes, you can, with low-profile jars provided you follow some guidelines.
Steam canning processing steps
- Put the required amount of water in the steam canner, as recommended by the manufacturer;
- Add a few squirts of vinegar to prevent jar outsides becoming cloudy;
- Put the rack into the canner, and turn the burner on to get it started heating. You may put the lid on the pot if you wish to be more energy efficient;
- Put the food in the jars;
- Put the lids on;
- Put the jars upright on the rack. (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!)
- Put the lid on the pot;
- You start timing only from when the steam reaches full temperature. If you have a gauged lid and the lid happened to show it was at a full head of steam when you took the lid off to put the jars in, then wait: the gauge will quickly fall, then climb back up to show when the new head of steam has been reached. The time needed to re-reach the head of steam does not count as part of processing time!
- You may adjust the stove burner heat lower, provided you maintain the full head of steam. In fact, you probably should: you are not trying to power the Flying Scotsman steam engine here and you don’t want it to super heat. Over time, you will learn the right setting for your stove burners;
- Let the canner steam for the prescribed time. Do not lift the lid off for any reason, or you will have to let it re-build a fresh head of steam and start timing all over again.
- When the time is up, turn off the heat, and remove the canner lid. (You can leave the canner where it is, or move it if you are able to safely move it and need the burner);
- Leave the jars as they are in the canner;
- Set a timer for 5 minutes;
- At the end of 5 minutes, remove the jars and place them on a towel or a wire rack somewhere away from cold drafts;
- Do not cover jars; do not touch rings (unless you are using Tattler lids); do not tilt jars or turn them upside down or try to clean or dry them now. Any water on them will quickly evaporate;
- Let jars sit untouched for 12 to 24 hours;
- Remove screw bands; check for proper seal of the flat lid;
- Put any that didn’t seal in the fridge and treat as opened;
- Wipe the jars down; label and date jars, store in a cool dark place with the screw bands off.
If you follow the steps above, your steam-canned food products will be 120% safe and of superb, long-lasting quality. The process is founded on research-based science with loads of margin for error built in to cover the variables of daily life.
The history of steam canning
The main concern about steam canning was that there were no confirmed, thorough, research-based and documented studies showing processing time required to kill off very real nasties such as E. coli, Salmonella and Listeria that could be present in jars of food. There were just “guesses” that using the same processing times as for water bath canning times “might” be sufficient.
Steam canner manufacturers just said use the same processing times as for tested recipes that call for boiling water processing. “The manufacturer ….. recommends identical processing times as those required for boiling-water bath treatments.”7 The issue of course is that the testing and certification of those recipes was for heat penetration at boiling water time durations — not steam.
Here is a 1914 ad for a steam canner. This steam canner was actually quite versatile: you could also use it as two roasting pans as well.
In the first decades of the 1900s, there was some confusion about the difference between the steam in a steam canner, and the steam in a pressure canner.
Initially, this newcomer was referred to as an ‘atmospheric steam canner,’ so that it would NEVER be confused with the Pressure Canner. The canner was called ‘atmospheric’ because the kettle is not sealed, and therefore the saturated steam inside it—not being under significantly more pressure per square inch than the air in the room outside—cannot get hotter than the boiling point of water in a utensil with an unsecured cover. Today, this piece of equipment is simply called a ‘steam canner.’ ” 8
In 1944, Virginia Cooperative Extension attempted to both clarify the difference, and ensure that people used them only for high-acid foods. The Extension also recommended extending boiling water processing times by one-third when translated to a steam canner:
A steamer should never be confused with a steam pressure canner. Most steamers have shelves for holding jars and a small amount of water in the bottom produces steam for processing. The time must be 1/3 longer in a steamer than in a boiling water bath. This method of processing is recommended for only fruits and tomatoes.” 9
From the 1950s onwards, interest in steam canning faded along with interest in canning generally.
Interest in steam canners was reborn in the 1970s, during America’s first energy crisis. To test the market, a few steam canners were advertised on the market again. Consequently, “in the 1970s there was some research into steam canning and low water level water baths (where the water didn’t cover the lids) because the first energy crisis had hit and there were concerns about how much energy pressure canning used, but the research was never completed.” 10
The research was never completed because the initial research wasn’t deemed reliable enough to be built upon: “In the 1970s (low-water water bath studies), they modified the typical situation enough in their data collection that thermal processing experts do not believe that the data they came up with would reflect what people would actually be doing at home and so they couldn’t endorse the recommendations from that study.” 11
In the 1980s, the University of Massachusetts also looked at steam canning. Here is the abstract from the paper that was published:
A comparison was made between steam canner and other conventional methods of home canning such as boiling water bath and pressure canner at 5 and 10 lb. of pressure. Several heat penetration studies were done and the processes were evaluated using sound thermobacteriological and mathematical basis. Only acid products such as tomato juice, tomatoes and apple sauce, were considered in this investigation. The final process times calculated for the three products and the come-up time needed for each equipment, indicates that steam canner method may be more efficient than other methods for home canning of acid-food products.” 12
Utah State found itself in the middle of controversy about the canning method:
There have been numerous questions concerning the safety of steam canning for more than 80 years. Unfortunately the issues still remain unresolved. Mostly due to the absence of definitive research. Utah State University has been placed in the middle of this imbroglio because a Salt Lake City steam canner manufacturer cites that its products and processes have been tested for safety by Utah State University’s Dr. Von Mendenhall. 13
In 2011, a joint effort began between the University of Wisconsin and the University of Georgia to produce a published, USDA recognized guide to home steam canning.
Dr. Barbara H. Ingham and Paola Flores at the University of Wisconsin-Madison are investigating the efficacy of steam canners. Through their work, they hope to resolve issues surrounding steam canners by developing safe steam canning processes and writing a consumer guide to steam canning. They anticipate publishing by the end of 2014…. For those consumers who still wish to use steam canners, regardless of recommendations to the contrary, we very strongly advise against steam canning any low acid foods…..” 14
This work was partly funded by a National Integrated Food Safety Initiative (NIFSI) grant awarded in December 2011. 15
In January 2015, Utah State University Extension quietly announced on its home page that it had tested steam canners and found them to be safe and adequate for jams, jellies and fruits if used according to instructions and safe canning procedures.
Note that Utah’s advice ended up being a bit more restrictive than the guidelines which were to end up being announced later that year in June. But perhaps because Utah State was already tainted by the controversy, their announcement didn’t seem to bear much weight, anyway.
The University of Wisconsin research with guidelines endorsing steam canning was released on 24 June 2015.
Ingham, Barb. Using an Atmospheric Steam Canner. University of Wisconsin Extension Blog Posting. 24 June 2015.
Steam Canning. In: Andress, Elizabeth L and Gerald Kuhn. Critical Review of Home Preservation Literature and Current Research. Athens, GA: University of Georgia, Cooperative Extension Service. 1983. http://nchfp.uga.edu/publications/usda/review/equip.htm#steam
Paola Willmore, Mark Etzel, Elizabeth Andress and Barbara Ingham. Home Processing of Acid Foods in Atmospheric Steam and Boiling Water Canners. Food Protection Trends, Vol 35, No. 3. May / June 2015. p. 150–160.
These links are just provided to help you plan the right steam canner that would work with your stove.
The “Back to Basics 400A 7-Quart Aluminum Home Steam Canner” has concentric rings (waves) on its bottom. Consequently it will not work with smooth stove tops.
The Victorio brand has three steam canners on offer, as of summer 2015.
All have temperature gauges. One complaint about the Victorio basic model VKP1054 was the wire rack that came with it; Victorio replaced that with a better flat rack sometime in 2014.
Victorio steam canner model VKP1054. Made of aluminum. Has concentric rings on bottom so cannot be used on any smooth top stoves.
Victorio steam canner multi-use model VKP1145. Made of aluminum. Has concentric rings on bottom so cannot be used on any smooth top stoves. Does both steam canning and water bath processing.
Victorio steam canner multi-use model VKP1130. Made of stainless steel, and has flat bottom so it can be used on glass and induction stove tops. Does both steam canning and water bath processing.
Ziedrich, Linda. The Joy of Pickling. Boston: Harvard Common Press. 2009. Page 23. Ed. She went to to say that she had to object to them because the USDA did, but that concern has been addressed as of June 2015. ↩
Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” Webinar. 27 February 2013. [37:36] Accessed January 2015 at http://nchfp.uga.edu/multimedia/video/nchfp.wmv ↩
Quote from Walmart site. http://www.walmart.com/ip/Back-to-Basics-Steam-Canner/2138510. Accessed May 2015. ↩
Ingham, Barb. Using an Atmospheric Steam Canner. University of Wisconsin Extension Blog Posting. 24 June 2015. ↩
Ingham, Barb. Using an Atmospheric Steam Canner. University of Wisconsin Extension Blog Posting. 24 June 2015. ↩
Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 62). Penguin Publishing Group. Kindle Edition. ↩
Cameron, Janet L. and Mary L. Thompson. Canning for the Home. Bulletin No. 128. Virginia Agricultural and Mechanical College and Polytechnic Institute and the United States Department of Agriculture, Cooperating Extension Division. Revised June 1944. Page 6. ↩
Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” Webinar. 27 February 2013. ↩
Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” Webinar. 27 February 2013. 38:00. Accessed January 2015 at http://nchfp.uga.edu/multimedia/video/nchfp.wmv ↩
Ramakrishnan, T.V. et al. Comparison of Steam Canner Processing with Other Methods of Home Canning. Journal of Food Processing and Preservation. Volume 11, Issue 1, pages 43-61. March 1987. ↩
Nummer, Brian A. Using a Steam Canner. Utah State Cooperative Extension. 6 September 2005. No. 002 (2005). http://extension.usu.edu/files/publications/newsletter/No__002.pdf ↩
Canning Controversy: What About Steam Canners? Clemson University Cooperative Extension Service. Clemson University, South Carolina. Accessed January 2015 at http://www.clemson.edu/extension/food_nutrition/canning/tips/42_steam_canners.html ↩
NSAC Blog entry 9 December 2011. Accessed May 2015 at http://sustainableagriculture.net/blog/food-safety-grant-awards-2011/ ↩