Plum Jam

1 . Stage

Inspect 8 half-pint jars for cracks and rings for rust, discarding any defective ones. Immerse in simmering water until jam is ready. Wash new, unused lids and rings in warm soapy water.

2 . Stage

Combine plums and water in a large pot over medium-high heat; bring to a boil. Reduce the heat to medium-low, cover, and simmer for 5 minutes. Stir in sugar, then add butter to reduce foaming if needed.

3 . Stage

Increase the heat to high and stir constantly until mixture comes to a full, rolling boil. Quickly stir in pectin and return to a full boil. Boil, stirring constantly, for 1 minute. Remove from the heat; skim off and discard any foam.

4 . Stage

Pack jam into hot, sterilized jars, filling to within 1/8 inch of the top. Run a clean knife or thin spatula around the insides of the jars to remove any air bubbles. Wipe rims with a moist paper towel to remove any residue. Top with lids and screw rings on tightly.

5 . Stage

Place a rack in the bottom of a large stockpot and fill halfway with water. Bring to a boil and lower jars 2 inches apart into the boiling water using a holder. Pour in more boiling water to cover jars by at least 1 inch. Bring to a rolling boil, cover, and process for 10 minutes.

6 . Stage

Remove the jars from the stockpot and let rest on a cloth-covered or wood surface, several inches apart, for 12 to 24 hours. Press the center of each lid with a finger to ensure the lid does not move up or down. Remove the rings for storage and store in a cool, dark area.