Place required number of clean 1 L ml mason jars on a rack in a boiling water canner. Cover jars with water and heat to a simmer (180°F/82°C). Set screw bands aside. Keep jars hot until ready to use. Preheating Bernardin® lids is not advised.

The sealing compound used for our home canning lids performs better at room temperature than it does pre-heated in simmering water (180°F). Simply wash lids in hot, soapy water, dry, and set aside until needed.

Preheating can lead to less vacuum being achieved during water bath canning, and to buckle failures during pressure canning. Wash tomatoes, remove stems and trim off bruised or discoloured portions.

To prevent juice from separating, quarter 1 lb (500 g) tomatoes (about 2 cup [500 ml]) and place in a large stainless steel saucepan over high heat. Stir and crush mixture until it boils rapidly. Then continue to slowly add and crush freshly cut tomato quarters to the boiling mixture.

Be sure to maintain a constant, vigorous boil while adding remaining tomatoes. When all pieces have been added and crushed, boil gently for 5 minutes before juicing. If juice separation is not a concern, simply slice or quarter tomatoes into a large stainless steel saucepan.

Crush, heat and boil gently for 5 minutes before juicing. To remove skins and seeds, press through a fine sieve or food mill. Discard seeds and skins. Return juice to saucepan; heat to boiling. Add 2 tbsp (30 ml) bottled lemon juice or 1/2 tsp (2 ml) citric acid to each 1 L jar.

If desired add 1 tsp (5 ml) salt per 1 L jar. Ladle hot juice into a hot jar to within 1/2 inch (1 cm) of top rim (headspace). Add one sprig of fresh herb to each litre jar. Using nonmetallic utensil, remove air bubbles and adjust headspace, if required, by adding more juice.

Wipe jar rim removing any food residue. Centre sealing disc on clean jar rim. Screw band down until resistance is met, then increase to fingertip tight. Return filled jar to rack in canner. Repeat for remaining juice.

When canner is filled, ensure that all jars are covered by at least one inch (2.5 cm) of water. Cover canner and bring water to full rolling boil before starting to count processing time.

At altitudes up to 1000 ft (305 m), process -boil filled jars - 45 minutes.* When processing time is complete, remove canner lid, wait 5 minutes, then remove jars without tilting and place them upright on a protected work surface. Cool upright, undisturbed 24 hours; DO NOT RETIGHTEN screw bands.

After cooling check jar seals. Sealed discs curve downward and do not move when pressed. Remove screw bands; wipe and dry bands and jars. Store screw bands separately or replace loosely on jars, as desired. Label and store jars in a cool, dark place.

For best quality, use home canned foods within one year.

Processing: At altitudes up to 1000 ft (305 m), process -boil filled jars - 45 minutes - 40 minutes.

Altitude-adjusted processing table: At altitudes up to 1000 ft (305 m), process -boil filled jars - 45 minutes