Wash grapefruit, score skin into quarters and remove peel. With a spoon, scrape bitter white pith from peel and discard. Slice the peel thinly. In a large, deep stainless steel saucepan, combine peel with water to cover generously. Bring to a boil over medium-low heat and boil for 10 minutes.

Drain and discard liquid. Return peel to saucepan. Working over a bowl to catch juice and using s sharp knife, separate grapefruit segments from the membrane. Place segments in saucepan and squeeze any juice from membrane into saucepan. Discard membrane and seeds.

Add 4 cups (1L) water to peel mixture. Bring to a boil over medium-high heat. Reduce heat and boil gently, stirring occasionally, for 10 minutes. Cover and let stand in a cool place (70 to 75ºF/21 to 23ºC) for 12 to 18 hours. Place 3 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. Place saucepan on medium-high heat and bring mixture to a boil, stirring frequently.

Boil until peel is tender, about 15 minutes. Remove from heat and measure fruit mixture. Return to saucepan and bring back to a boil. Maintaining boil, gradually stir in 1 cup (250 ml) sugar for each cup (250 ml) of fruit. If desired, add 1/2 tsp (2 ml) butter or vegetable oil to reduce foaming.

Boil hard, stirring frequently, until mixture reaches gel stage, about 30 minutes. Remove from heat and test gel. If gel has been reached, Skim off foam. Gel Stage Tests Remove pot from heat while conducting selected gel test: o Dip cool, metal spoon into marmalade.

Lift spoon moving it away from steam. Gel Stage is reached when mixture sheets off spoon. o Place spoonful of hot mixture on chilled plate; place plate in freezer until cooled.

Gel is achieved when product does not run together when separated with spoon. o Cook mixture to 220°F (104°C) or until it reaches a temperature that is 8°F (4°C) above the boiling point of water at your elevation.

Quickly ladle hot marmalade into a hot sterilized 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 hot 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