Steam Canners: What the Research Covers, and Why Low-Acid Food Is Out

A steam canner uses less water than a big pot. That is welcome on a hot afternoon of jam. It is also easy to confuse with something it is not, so let's sort it out.

Do you recommend one?

No. We hold no maker's document for a steam canner, and we have no Amazon listing we could vouch for.

If you own one of the two models Wisconsin names, the conditions below are your starting point. If you want a method that is in the USDA guide, a water bath canner does the same jobs.

If you want beans, carrots or stock on the shelf, you need a pressure canner. A steam canner has no part in that.

What is a steam canner?

Oregon State describes a shallow base, a wire rack and a domed lid with vent holes. Clemson says jars sit on a rack above a water pool, and steam from the boiling water heats them. Clemson says it uses less water than a boiling water canner, gets hot faster and needs less energy.

It has no pressure at all. The steam is only as hot as boiling water. So on the heat question it sits with water bath canning, even though it looks like neither a water bath pot nor a pressure canner.

Who says what?

The older USDA line and the newer research are both on the record, and readers often see only one. Neither says anything in favor of low-acid food in this equipment.

What are the rules for using one?

These come from the National Center's Burning Issue. We leave out the numbers. They belong with your tested recipe, and the National Center's page has them.

• Right foods only. Naturally high-acid foods, or foods with acid properly added.
• A tested recipe. Oregon State says most tested boiling-water recipes for these foods can be adapted.
• Let the air out first. Air must be vented, and the steam must be as hot as boiling water from the start to the end.
• Warm jars. Jars are warmed and filled, with as little waiting as possible before processing.
• A limit on total time. The National Center caps the total time, altitude change included. Clemson explains why: the water has to last, and you cannot open the canner to add more. So a recipe with a long process does not fit.
• Adjust for altitude. Times must be adjusted, as with any recipe at height. See our altitude page.
• Keep it closed. Do not open the canner during processing, even to add water.
• Cool gently. Jars cool in still air, with no forced cooling.

Oregon State and Clemson both warn against boiling too hard, because the canner can run dry. Oregon State says a batch that boils dry is under-processed. It must be redone with new lids.

Which models does the research name?

Wisconsin and Oregon State name the same two: the Back to Basics and the Victorio. Both have a shallow base, a rack and a tall domed lid, says Wisconsin. Wisconsin says the Victorio's built-in temperature gauge was fairly accurate. It says other steam canners are not recommended.

We have neither model in our product data. We found no maker's document to read, so there is no product box on this page. If you shop for one, look for the model name in the listing and read the maker's own page. A listing that only says "steam canner" tells you little.

What about plug-in steam canners?

People search for plug-in steam canners and for a Ball steam canner. Here is what we can and cannot say.

• Plug-in steam canners. None of the pages we read mentions them. Wisconsin makes no recommendation for other appliances. Please do not carry its findings over to a plug-in machine.
• The Ball EasyCanner. Ball sells it as a water bath canner, also with cooking and steaming settings. A steaming setting is not steam canning as Wisconsin studied it. See our EasyCanner page.
• The NESCO NPC-9. NESCO's guide has a low-pressure or steam section. That is not what the Wisconsin research covered. It is also a combination machine. Penn State Extension says it cannot recommend combination canner and cooker appliances, because research on their safety is missing. Penn State names no brand. Putting the NESCO NPC-9 in that group is our reading. See what the experts say about plug-in canners.

These are different kinds of machine from a dome-style steam canner. What is said about one does not carry over to another. Our guide to machine types lays them out.

Can I use the booklet recipes?

No. Oregon State warns that booklets packed with steam canners are not research-based and may under-process food. Clemson says maker recipes are not considered research-tested.

Oregon State points to current tested recipes from the National Center for Home Food Preservation, your state's university extension office (free local food-safety advice) or the latest Ball Blue Book. The tested recipes page shows where to find them. Our page on canning books covers the editions.

Read your maker's instructions too, for how the pot works. Our manuals page helps you find them.

Which way should I go?

Start from what you want to can

• If you want jams, fruit and pickles and prefer a method that is in the USDA guide

  Water bath vs. pressure

• If you would like a plug-in machine for those same high-acid recipes

  Electric water bath

• If you want low-acid food such as vegetables or meat on the shelf

  Stovetop pressure canners

To see all the machines side by side, start at our overview. A steam canner can be a pleasant tool for the right jars. Knowing its limits is most of the job.