Place 7 clean 250 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. Using a vegetable peeler, remove peel form half of one orange. Cut peel into very thin slivers, about 1 inch (2.5 cm) long, and set aside.

Squeeze juice from both oranges into a measure, adding water if necessary to yield 1cup (250 ml). Measure sugar and set aside. In a large, deep stainless steel saucepan, combine orange juice, slivered orange peel and rhubarb. Whisk in pectin until dissolved.

Bring to a boil over high heat, stirring constantly. Add all of the sugar. Stirring constantly, return mixture to a full rolling boil that cannot be stir down. Boil hard, stirring constantly, for 1 minute. Remove from heat and skim off foam.

Ladle hot 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 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 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 a 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, turn stove off, 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