Toss the raspberries and sugar together in a large, heavy-bottomed saucepan and allow the mixture to sit for about half an hour — this provides the berries with ample time to release their juices.
Rinse the berries as lightly as possible. If they're organic, there's no need to rinse them at all.
Process
Cook the mixture over medium heat, taking care to see that it doesn't burn while stirring occasionally with a wooden spoon.
When the mixture begins to thicken, it's time to step up your stirring game because as the natural sugars in the berries as well as the added sugar starts to concentrate, it's at increased risk of becoming scorched. It should reach the desired thickness within half an hour to 40 minutes on the stove.
To test whether the mixture is ready for the jar, place a small amount on a cold plate and place it in the freezer for about two minutes and then remove it and drag your finger through the mixture. If it's ready, it won't fill in the area your finger has cleared.
Pour the mixture into the jars and give them a standard hot water bath for 10 minutes.