Crush or mash the raspberries with a masher or in a food processor to the desired texture.
Combine the pectin, lemon juice and ¼ cup of the sugar, then add to the raspberries.
Place mixture into a large pot and bring to a full boil, stirring continuously. Combine in the remainder of the sugar and return to a boil for 1 minute. Remove from heat and spoon off any foam.
Immediately transfer jam into still hot, sterilised jars, filling to within 1cm of the top. Clean off any jam spills from the jar rims. Place lid discs onto the jars and screw on the rings. Let the jars cool for 20 minutes.
Setup a large, deep pot with a rack in the bottom. Half fill the pot with warm water. Place jars in, making sure they are not touching each other. If you don’t have a rack, use an upside down cake pan in the bottom. This is to keep the jars from touching the bottom of the pot and getting too much direct heat. Add extra water until the jars are covered.
Cover the pot with a lid and boil for 10 minutes.
Remove jars to cool and leave overnight to seal. Once the lid is sealed, remove the rings. Store for up to a year in the pantry.
