Plum Jam is one of the most popular of home-made jams. Plums have a high pectin content so the jam sets easily. Choose firm, ripe plums, discarding any that are bruised.
3 lb. plums, halved and stoned
10 fl. oz. water
3 lb. sugar
In a preserving pan or large saucepan, bring the plums and water to the boil over high heat.
Reduce the heat to moderate and cook for 20 minutes, or until the plums are soft. Add the sugar and stir until it has dissolved.
Bring the jam to the boil and boil for 15 minutes or until setting point is reached.
To test for setting point, remove the pan from the heat and spoon a small amount of the jam on to a saucer. Allow it to cool. If it sets and wrinkles when you push it with your finger, the jam is ready. If not, return the pan to the heat and continue boiling, testing frequently. If you use a sugar thermometer, the jam should register 220 F to 222 °F.
When setting point has been reached, remove the pan from the heat. With a slotted spoon, skim off the scum from the surface of the jam.
Pour the jam into clean, dry, warmed jam jars. Seal each jar with a jam cover, label and store in a cool, dry place.