Make sure the mixture boils constantly and vigorously while you add remaining tomatoes. Lower heat and simmer five minutes after all tomatoes are added. If you are not concerned about sauce separating, simply slice or quarter tomatoes into a large saucepan. Crush, heat and simmer for five minutes before pressing. Press either type of heated tomatoes through a sieve or food mill to remove skins and seeds.
Heat tomatoes again to boiling.
Lower heat and simmer in a large saucepan until sauce reaches desired consistency. Add bottled lemon juice or citric acid to jars using directions at beginning. Add 1 teaspoon canning salt to each quart jar if desired. See Table 2 or 3 for process times. For best quality and nutritional value, use home-canned tomato products within one year.