You want to start by cleaning in sterilizing your jars where the jam will be stored. Also place a plate into the freezer so that it can chill.
Take half of your raspberries and place them into a preserving pan and add in your lemon juice. Next, mash the berries to a pulp, and you can use a potato masher to do that.
Cook the berries for about 5 minutes and then run through a sieve over a bowl. When the juice has drained out, use a wooden spoon to push the pulp through the seeds until all that is left in the sieve are the seeds.
Drain the juice and pulp into the preserving pan and add in your sugar, stirring gently. Heat on a low heat and add into rest of your raspberries. Cook until the mixture starts to boil.
Allow it to boil for five minutes and then remove the raspberries from the heat. Put a little bit of the jam onto the chilled plate to test it. As you push your finger through the jam, it should start to wrinkle and should look like jam. If it doesn’t have the right texture or consistency, then it needs to be boiled for longer. You can continue boiling for another 2 minutes and then repeat the test.
The jam should then be poured into jars and sealed up. It will stay good for a year if you do not open it. After you open the jam, be sure to store it in the refrigerator.