894 B
Water Bath Canning
Water bath canning submerges filled jars in boiling water. The contents reach 212°F (100°C) at sea level and no higher, which is why this method is limited to a specific class of foods.
Only high-acid foods
Water bath canning is safe only for high-acid foods — those with a pH of 4.6 or below. That means most fruits, jams and jellies, pickles, and properly acidified tomatoes.
Tomatoes sit close to the line. Modern varieties are often above pH 4.6, so tested recipes call for added bottled lemon juice or citric acid. Use bottled lemon juice, not fresh: fresh juice varies in acidity.
Method
Cover the jars with at least one inch of water. Start timing when the water reaches a full boil, and add time for altitude — 5 additional minutes for 1,001 to 3,000 feet, and more above that.
Never use this method for green beans, corn, meat, or soup.