Place 7 clean 250 or 236 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, hull and crush strawberries, one layer at a time. Measure 2 cups (500 ml); set aside. In a large, deep stainless steel saucepan, bring mint and water to a boil.

Cover and let steep 10 minutes. Discard mint leaves. Finely chop or pulse rhubarb in a food processor; measure 1 3/4 cups (425 ml); add to mint water. Return mixture to a boil, cover and boil gently until rhubarb softens, about 2 minutes. Add strawberries, lemon juice and sugar.

Over high heat, bring mixture to a full rolling boil. Stirring constantly, boil hard 1 minute. Remove from heat. Immediately stir in Liquid Pectin, mixing well. Skim off foam. Ladle jam into a hot jar to within 1/4 inch (0.5 cm) of top of jar (headspace).

Using nonmetallic utensil, remove air bubbles and adjust headspace, if required, by adding more jam. Wipe jar rim removing any food residue. Centre sealing lid 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 jam. 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 - 10 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 lids 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 - 10 minutes - 10 minutes.

Altitude-adjusted processing table: At altitudes up to 1000 ft (305 m), process -boil filled jars - 10 minutes