Using Water Bath Canners and Steam Canners
Reading Time: 8 minutes
Two canner styles are suitable for processing high acid foods: water bath canners and steam canners. Either type is a good starting place for anyone just learning to put up home canned foods; both are easier to use than a pressure canner (required for processing low acid foods). In subsequent issues, we’ll examine steam canners and pressure canners. Here we’ll look at water bath canners, also called boiling-water canners. In choosing a water bath canner, consider such things as the size you need for the amounts of food you plan to can, the size and style that best fits your cooktop, and the canner’s construction in relation to its durability and price.
Water bath canners may be made of stainless steel, aluminum, or steel coated with porcelain enamel. Stainless steel is the most expensive, but is also the most durable and the most versatile, as it may double as a stockpot. An aluminum canner is less expensive than one made of stainless steel, but I wouldn’t use it for anything other than canning food in sealed jars, because of the possibility of aluminum leaching into the food. Also the really cheap canners made of low gauge aluminum dent rather easily.
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Porcelain enamel coated steel is the traditional looking canner — the one you might remember Grandma using. It is usually black or dark blue with white speckles, although modern ones come in other colors.
The chief disadvantage to enameled steel is that you have to be super careful with this type of canner, because a ding easily causes a chip of enamel to break off, and where the enamel is missing, the steel rusts. Eventually, the pot will rust through and sprout a leak. I have successfully salvaged such canners by sealing leaks with an epoxy steel hardener called J-B Weld, but I wouldn’t use a patched vessel for any other purpose than to can food in jars.
Stainless steel and aluminum canners usually have smooth bottoms, while enameled canners generally have ridged bottoms. If you have a gas or electric coil cooktop, both types of bottom work equally well. If you have a smooth cooktop, you must use a canner with a flat bottom for even distribution of heat, and if your smooth cooktop is the induction type, the canner must be stainless steel. (Heat sources suitable for canning will be discussed in detail in the May/June 2017 issue.)
A canner should have a lid. The tighter the lid, the less steam will escape when the water boils, and the less heat you’ll need to keep the water boiling. Some canners have a glass lid that conveniently lets you see when the water comes to a boil so you will know when to start your timer.
A canner also comes with a removable rack that keeps your jars from touching the bottom of the canner, so boiling water can circulate underneath. The typical canning rack is made of heavy gauge wire and has handles that may be hooked over the rim of the pot. As you fill your jars, you set them into the rack; when the rack is full you unhook the handles from the pot’s rim and lower the jar-filled rack into the boiling water in the canner. A disadvantage to this type of rack is that it may not easily accommodate smaller size jars. Some canners come with a flat perforated rack, which is handier because it is suitable for jars of any size.
You don’t actually need a special pot to use as a water bath canner. A regular stockpot or any large pot will do, provided it’s tall enough to cover the food-filled jars with two inches of hard-boiling water and has a rack to hold the jars off the bottom of the pot. A variety of replacement canning racks are available on line, some of which should be the right size to fit whatever pot you might want to use for canning. A round cake cooling rack might also fit.
An alternative to a water bath canner is an atmospheric steam canner, to be discussed in the March/April 2017 issue. You may also use a pressure canner for boiling water processing, to be described in the May/June 2017 issue.
Water bath canners come in several sizes. The standard size holds seven quart- or pint-size jars. Don’t be fooled by the stated capacity, which would be something like 21 quarts. That’s how much water the canner holds, not how many jars may be canned at once. The water bath canner needs to be deep enough to cover your canning jars with one to two inches of water at a rolling boil, with at least two more inches of air space to prevent vigorously boiling water from slopping out of the canner.
Canners come in sizes that are smaller or larger than the standard size. I have a canner that holds seven narrow-mouth pint jars or three wide-mouth pints, but isn’t sufficiently tall to hold enough water to cover quart jars. I also have a jumbo size canner that will process nine quart or pint-size jars at a time.
Over the years I have accumulated several canners of varying sizes. To keep track of how many jars each one holds, I made a table listing all my canners in the first column, followed by four additional columns for jar sizes: quart, wide mouth pint, narrow mouth pint, and half pint. In these columns I noted how many of each size jar each canner will hold. If I’m putting up seven quarts of tomatoes, for instance, the table tells me to use my regular size stainless steel canner. If I have eight quarts, I use my larger aluminum canner. If I have nine quarts, I use the jumbo enamel canner.
Of course, if you aren’t sure how many jars you will fill, it doesn’t hurt to use a too-large canner (other than wasting energy boiling extra water). You may occupy the empty space with unsealed jars full of water. But it’s discouraging to have a canner full of hot water and ready to process your jars, only to discover that you filled one more jar than the canner will hold.
If you have only one water bath canner, you might adjust your recipe quantities to fill the number of jars your canner holds. In my canning notebook, for instance, my tomato page indicates that 19 pounds of tomatoes will fill seven quarts, the amount a standard-size canner will accommodate at one time.
Water Bath Procedure
To use a water bath canner, follow these steps:
1. Put fresh water in the canner until it is about half to two-thirds full and start warming the water. If you aren’t sure how much water will be needed to cover the size and number of jars you will be canning, warm a second pot of water. If the amount of water in the canner isn’t enough to cover the filled jars by at least an inch, you’ll need to add water. Since you don’t want to cool the heated water by adding cold water, you’ll be glad to have extra water already heated. If, on the other hand, the amount of water in the canner is so much it overflows when you put in the filled jars, scoop out some of the water with a ladle or small saucepan.
2. Heat the water in the canner, but don’t bring it to a boil yet. Doing so may cause the cooler jars to crack when they are lowered into the boiling water. Rapidly boiling water may also cause jars to tip over when you start putting them into the canner.
3. Fill hot, clean jars according to the recipe you are following for the specific type of food you are canning. Reliable recipes booklets come with most canners, or may be found online at such sites as nchfp.uga.edu and freshpreservingstore.com, which among other things will tell you whether the food may be raw packed or must be hot packed (heated before being processed).
4. Hook the handles of the canner rack over the top edge of the canner and load it with jars as they are filled and fitted with lids and bands. When all the jars are on the rack, lower the rack into the hot water. If your rack is the flat perforated type, drop it into the bottom of the canner and use a jar lifter to place jars one by one into the water.
5. If necessary, adjust the water level in the canner so the tops of the jars are covered by at least one inch of water for a processing time of less than 30 minutes. If the processing time is greater than 30 minutes, cover the jars by two inches of water, since more water will evaporate during the longer processing period.
6. Put the lid on the canner, turn the heat to the highest setting, and bring the water to a vigorous boil.
7. As soon as the water comes to a full rolling boil, adjust the heat to maintain the full boil and set your timer for the amount of processing time recommended for the food you are canning. If your elevation is above 1,000 feet, be sure to adjust the time according to the Elevation Table below.
8. When the time is up, turn off the heat, remove the lid from the canner, and leave the jars in the hot water for five minutes more.
9. Using your jar lifter, remove the jars one by one, without tilting them to remove residual water floating on top of the lids. Place the jars, one inch apart, on a rack or thick towel away from drafts.
10. Let the jars cool for at least 12 hours before removing the bands and testing the seals, as described in the July/August 2016 installment of this series. If you finish canning in the afternoon, for instance, let the jars cool until the next morning before washing them and storing them in the pantry.
Canner Rack— A shallow rack that allows boiling water to circulate underneath jars being processed.
Hot Pack — Cooked or preheated food used to fill canning jars for processing.
High Acid Foods — Pickles, fruits, jams, jellies, juices, and other foods having a pH less than 4.6.
Jar Lifter — A device for safely putting jars into or removing them from a hot canner.
Raw Pack — Fresh produce that has not been cooked or preheated before being placed in jars for processing; also called cold pack.
Water Bath Canner — A large vessel in which jars of food are processed in boiling water.
Water Bath is for High-Acid Foods Only
Only high acid foods may be safely canned by the water bath method. High acidity in this case is defined as having a pH less than 4.6. Acidity at this level prevents the growth of toxic botulism (spores of the bacterium Clostridium botulinum), which cannot be killed at the temperature of boiling water. High acid foods include pickles and most fruits, fruit juices, jellies, jams and pie fillings. Examples of high acid foods are: apples, apricots, berries, cherries, grapes, peaches, pears, pineapple and rhubarb.
Tomatoes are a borderline case, since their acidity is right at the safety line. Current recommendations are that if you can tomatoes by the boiling water method, ensure adequate acidity by adding 2 tablespoons of bottled lemon juice or ½ teaspoon citric acid per quart.
Low acid foods—those with a pH greater than 4.6—must be pressure canned. Pressure canners will be discussed in the May/June 2017 issue.
Keep It Boiling
The water surrounding jars in the canner must continuously boil throughout the entire processing time. Three things can reduce boiling: turning the heat source too low, lifting the lid while jars are being processed, and adding more water to keep the jars covered.
If the water boils so hard it slops out of the canner, you may need to turn the heat down a tad. Just make sure enough heat is being applied to maintain a full boil.
Reasons for lifting the lid are to see if the water is boiling, to make sure the jars remain covered in boiling water, and to add more water if too much has steamed or boiled off. Here’s where a canner with a glass lid comes in mighty handy.
With a little experience you can learn to tell the water is boiling by the sound, and sometimes by seeing steam coming out around the lid. Experience will also tell you how much water to put in the canner initially so it won’t steam or boil off before the processing time is up.
If the jars do not remain covered during the entire processing time, you will need to add more water, which must be first brought to a boil. Pouring even a small amount of cool water into the canner during processing can cause the canner water to stop boiling. If boiling stops, bring the temperature back up until the water returns to a full boil and reset your timer to the full processing time.