Place 4 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. In a large deep stainless steel saucepan, combine pears and sugar. Squeeze juice from limes; add to fruit-sugar mixture. Let stand 1 hour. Remove remaining pulp from limes.

Cut rind into very fine strips. In a small stainless steel or enamel saucepan, cover lime strips with cold water; bring to a boil and cook about 15 minutes, until peel is tender and most of liquid is evaporated. Drain liquid, adding it to pear mixture. Set rind aside.

Stir chopped ginger into pear mixture; bring all these ingredients to a full rolling boil. If desired, add 1/2 tsp (2 ml) butter or margarine to reduce foaming. Boil rapidly, stirring frequently, until marmalade reaches gel stage, about 15 minutes. (Gel test: Remove mixture from heat.

Place a spoonful of mixture on plate in freezer for a few minutes; mixture is gelled when it does not run together when separated.) Remove from heat; stir in lime rind and skim off foam, if necessary.

Quickly ladle hot pear marmalade 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 marmalade. 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 marmalade. 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 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 - 10 minutes - 10 minutes.

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