Prepare the jars first. Wash and sanitize. You can use the dishwasher on the hot wash and hot dry session to sanitize. Set aside on a towel to dry.
Measure out the berries and wash them. Put them in a large stainless steel pot.
7 cups fresh blackberries
Mix the sugar and the dry pectin together, then add to the pot of berries. Heat on medium low until the berries juice up and dissolve the sugar, stirring the pot to make sure nothing sticks. Add the lemon juice.
3 cups white granulated sugar, 3 ½ tablespoon Powdered Pectin, ½ cup lemon juice
After sugar is dissolved, turn the heat to medium high and bring the pot to a rolling boil. If foam develops, either scoop it off and discard, or stir it down. You will cook on the boil for 8 minutes. Then reduce heat and simmer, stirring frequently for another 12 minutes.
The preserves should fall off the flat of a wooden spoon slowly, with a drip in two places on the spoon, not just one drip in the middle. If not quite ready, cook up to 3 more minutes, checking for jell in 1 minute intervals. Remove pot from heat and ladle into prepared jars.
Wipe the jar rims with a damp cloth, seal with the disc lids, and tighten the bands.
Let the jars sit on the counter to cool. You will hear little pop sounds as the sealing discs are sucked in with a vacuum seal. You can store in your refrigerator for up to 6 months.
If you want to store in your pantry, use the Ball Hot Water Canning Method to hot water bath process them. See the notes for the link to the instruction guide. They should process for 10 minutes.