Canning Blackberry Jam
22 Steps -- Step 12

Bring Mixture to a Rolling Hard Boil

Now apply high heat and bring the mixture to a full rolling boil. A full rolling boil is a boil you cannot stir down. During this time we are constantly stirring the pot with a long wooden spoon. We say long because you do not want a blob of boiling jam to land on your hand. Now while a "watched pot never boils" (false), a watched stirred pot doesn't stick or scorch.