In a large, deep stainless steel pot stir fruit, sugar, lemon juice and butter. Over high heat, bring mixture to a full rolling boil that cannot be stirred down. At that point add liquid pectin, squeezing entire contents from pouch. Return to boil; boil hard 1 minute, stirring constantly. Remove from heat and skim off foam.

Fill the hot boiled jars with the hot jam. Leave a space of about 1/4 inch (0.5 cm) of top of jar. Wipe jar rim removing any food residue. Centre hot sealing disc on clean jar rim. Screw band down. Place jars back in the canner (boiling pot). 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, 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 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.