Place the fruit, water and sugar in a jam pan. Attach your jam thermometer to your pan if you have one.
355 g damsons, 250 g redcurrants, 500 ml water, 480 g granulated sugar
Cook on low heat for 15-20 minutes until the sugar has dissolved and the fruit has softened.
Bring the pan to the boil and boil hard for 10 minutes, until the thermometer shows the jam has reached the setting point (marked "jam" on my thermometer). This is 105℃ / 220℉.
If you don't have a thermometer you can test for setting as described in my gooseberry jam recipe.
To remove the redcurrant seeds, pass the jam through a muslin bag using a jam strainer. As this jam sets very quickly due to all the pectin in the fruit, I squeezed the liquid jam through the muslin so that I could jar it while still hot.
Place your jam in your sterilised jam jars. I wash mine in hot soapy water then place them in the oven at 100 degrees for ten minutes to sterilise, but there are other methods you can use.
Place the jars in a dark place for 24 hours to set. This recipe made three small jam jars.