Improvise a water bath canner from any food-safe pot that is tall enough to cover the lids with about 2 inches of water, fitted with a rack so no jar touches the heated base. It is safe only for high-acid foods below pH 4.6, because it cannot exceed the boiling point of water. Never use a drum or tank that once held fuel, chemicals or pesticide, and never use galvanised metal for acid food.
Part of Canning & Pressure Preservation
An improvised water bath canner is a large pot, a rack and a lid used to hold sealed jars in boiling water for a timed process.
The Pot Must Cover The Jars And Keep Them Off The Base
This canner serves only foods below pH 4.6 (see Acid levels and safety thresholds), since it cannot exceed the boiling point of water.
The water bath works by boiling water surrounding the jars on all sides. Two geometric requirements follow. The water must be deep enough to cover the lids by about 2 inches, as the parent article specifies, so that every part of the jar is held at the boiling temperature and the level stays above the lids as water boils off. And the jar bottoms must be lifted clear of the base, because a jar standing directly on a hot surface experiences a sudden thermal shock and may crack.
A pot at least 12 quarts is the parent article’s minimum. For a quart jar standing upright, the pot has to be deeper than the jar plus the rack plus 2 inches of water, so the working depth is the arithmetic: jar height plus rack height plus 2 inches, plus a few inches for boil-over. Measure your tallest jar before choosing the pot.
What You Need
- A pot or kettle deep enough for the tallest jar plus rack plus 2 inches of water plus boil space; with a lid, to bring it to boil faster
- A rack, which can be:
- a wire cooling rack cut to fit
- a layer of screw bands (jar rings) laid flat on the bottom
- wooden slats wired together, accepting that wood deteriorates and floats
- a folded cloth, which works only briefly and then deteriorates
- A jar lifter or tongs and a heat-proof surface to set jars on
- A heat source that holds a steady full boil, from a stove to an outdoor fire with a stable grate
Which Metals And Containers Are Not Acceptable
The parent article suggests “even a clean metal drum over an outdoor fire”. Treat that with care. Use a drum only if you know it held nothing but food (Container Selection: Choosing Safe Vessels gives the ranking of salvaged vessels, and its rule is that a container that ever held fuel or pesticide never holds food or water again). Avoid galvanised steel, whose zinc coating dissolves in acid and gives off fumes when heated. A rusty vessel can contaminate the water and is a poor choice. Stainless steel and enamel-coated steel are good; aluminium is acceptable for water, but acid food should not sit in direct contact with it.
Method: Run The Bath
Step 1: Fill the pot about half full of hot water and place the rack.
Step 2: Lower filled, sealed jars onto the rack, upright, not touching each other or the pot walls. Add boiling water until the lids are covered by about 2 inches.
Step 3: Cover, bring to a full rolling boil, and begin timing only when the boil has returned (the parent article’s rule).
Step 4: Hold a steady boil for the full time in the tested schedule. If the water level falls so the lids show, add boiling water.
Step 5: Lift jars out with the lifter and set on a towel; leave for 12-24 hours.
Worked Example: Pot Depth
For a quart jar roughly 6.5 inches tall (a typical jar; check yours), with a 1-inch rack and 2 inches of water over the lid, the water must be at least 6.5 + 1 + 2 = 9.5 inches deep. Allow 2 more inches of free space for the boil. The pot interior should be about 11.5 inches high. A pot’s stated volume says nothing about its depth: a wide, squat 12-quart pot may be too shallow for quarts although it holds enough water. Measure the depth rather than rely on the stated volume.
Common Mistakes
- Starting the clock when the jars go in. The process time starts when the water returns to a full boil after loading.
- A rack that lets jars tip or touch. Touching jars crack and also shade each other from the boil.
- Adding cold water to a boiling pot with jars in it. The jars can crack from the sudden temperature drop.
- Using the bath for a low-acid food. See the safety block.
Safety
Scalding water and cracked jars
A pot holding boiling water and many glass jars is heavy and hot. Lift jars with a jar lifter, never bare hands, keep children out of the area, and never lift the pot with water in it. Keep the pot on a stable base; a toppled canner scalds. The water bath alone does not make low-acid food safe: it cannot exceed the boiling point of water (Water bath vs pressure canning).
What’s Next
- Learn next: Water Bath Canning (High-Acid) — the foods and methods this canner is for
- Combine with: Processing times and headspace — the numbers that go with the pot