Tomatoes are normally considered high in acid,but the acid level isn't quite high enough for canning. To bring tomatoes up to the proper acidic level, vinegar, lemon juice or citric acid must be added. Add 4-tbsp vinegar, 2-tbsp of bottled lemon juice or 1/2-tsp of citric acid per quart of tomatoes. For pints, use 2-tbsp vinegar, 1-tbsp lemon juice or 1/4-tsp citric acid Processing time doesn't start until the canner is brought back to a rolling boil Spoilage signs are a swollen lid, leaky