Sterilize canning jars and prepare two-piece canning lids according to manufacturer s directions. To prepare fruit. Sort fully ripe plums, wash, cut into pieces, and remove pits.

If flesh clings tightly to pits, cook plums slowly in a small amount of water for a few minutes until they are softened, then remove pits. Crush fruit. To make jam. Measure crushed plums into a kettle. Add pectin and stir well.

Place on high heat and, stirring constantly, bring quickly to a full boil with bubbles over the entire surface. Add sugar, continue stirring, and heat again to a full bubbling boil. Boil hard for 1 minute. Remove from heat; skim.

Fill hot jam immediately into hot, sterile jars, leaving 1/4 inch headspace. Wipe rims of jars with a dampened clean paper towel; adjust two-piece metal canning lids. Process in a Boiling Water Canner .

Processing: Process Hot, Half-pints or Pints, boiling-water canner, 0 - 1,000 ft - 5 minutes.

Altitude-adjusted processing table: Table 1. Recommended process time for Plum Jam in a boiling water canner. / Process Time at Elevations of / Style of Pack - Jar Size - 0 - 1,000 ft - 1,001 - 6,000 ft - Above 6,000 ft / Hot - Half-pints / / or Pints - 5 min - 10 - 15