Step 1: Prepare the jars

Sterilize your jam jars by washing them in hot, soapy water, rinsing well, then placing them in a warm oven at 120°C (250°F) for 10–15 minutes. Let them cool while you make the jam.

Step 2: Cook the fruit

1. Place the blackberries in a large saucepan over low to medium heat.

2. Cook gently for 5–10 minutes, stirring often, until the berries begin to soften and release juice.

Step 3: Add the sugar

1. Add the sugar to the warm fruit.

2. Stir continuously until the sugar has completely dissolved—do not let the mixture boil yet.

Step 4: Boil the jam

1. Once dissolved, bring the mixture to a rolling boil.

2. Boil rapidly for 10–12 minutes, or until it reaches 105°C (220°F) on a jam thermometer.

3. Alternatively, test for the setting point using the chilled plate method: place a spoonful of jam on a cold plate, wait 30 seconds, then push it with your finger—if it wrinkles, it’s ready.

Step 5: Skim and jar

1. Remove the pan from the heat and skim off any foam from the surface.

2. Let the jam sit for 5 minutes to help the fruit settle evenly.

3. Carefully ladle into warm sterilized jars, seal tightly, and label once cooled.