Canning Blueberry Jam
20 Steps -- Step 10

Add Butter and Boil

Next we will add a pat of butter (we use margarine). This will help to hold down the foam when it gets boiled. Next we apply high heat to bring the mixture to a full rolling boil. A full rolling boil is one that cannot be stirred down,.You need to constantly stir it during this stage. Scorched jam doesn't go over too well.