Every August the tomatoes come in like the tide, and every August my neighbors ask the same two questions: Do I have enough acid? and How long in the bath? This page is my answer, written down so I stop repeating myself.
Rule one: water-bath is for high-acid only
Boiling water reaches 212°F at sea level and not much more. Boiling alone will not kill the bacteria that cause botulism in low-acid foods. That’s why we can only water-bath fruits, pickles, tomatoes with added acid, jams — anything at pH 4.6 or below. Everything else — green beans, corn, meat — belongs in a pressure canner, or it doesn’t belong in a jar at all.
Rule two: trust a thermometer, not a memory
As elevations rise, water boils cooler, so the bath must run longer. At sea level, 212°F; at my altitude I add a few minutes. The math below does that for you. And always start timing only when the bath returns to a full rolling boil after the jars go in — a lost five minutes there is how seals fail quietly.
Rule three: a clean rim is a sealed jar
Wipe the jar rims with a clean, damp cloth before the lids go on. A crumb of salsa between lid and glass is a guaranteed unsealed jar and a sticky shelf by morning. Leave ½ inch headspace, no more, no less.
Your time calculator
Water-bath minutes at your elevation
This is a helper, not a replacement for the current USDA Complete Guide to Home Canning. When in doubt, look it up fresh — the guide is updated and free.
The philosophy of the jar
Canning is the opposite of hurrying. You wash, you blanch, you stir, you wait for the boil, you listen for the pop of seals on the counter at dusk. What you get is not just food — it’s January tasting like August, and the quiet assurance that when the power goes out, your pantry has your family’s back. That’s the whole reason I do it.