1. Wash blackberries and remove stems. Place blackberries in large stock pot with about 1 c. water to keep them from sticking to bottom of pot. Bring to boil and simmer for about 10 minutes, or until blackberries are soft.
2. Extract juice from blackberries with a jelly bag or fine mesh strainer. Measure juice, adding a little water if necessary to get exactly 3 1/2 cups of juice.
3. Pour blackberry juice into a large stock pot. Sprinkle the pectin on top of the juice and use a whisk to mix it together. Stirring constantly, heat until boiling. Boil for one minute.
4. Add the butter and return to a boil. Add the sugar to the pot all at one time (measure it and have it ready ahead of time). Stir until sugar is dissolved. Return to a boil and boil for one minute.
5. Related Article: Honeysuckle Jelly Canning Recipe: A Sweet and Floral Delight

Canning Process

1. Before filling your jars, make sure they are sterilized and ready to go.
2. You can sterilize your jars by boiling them in a pot of water for 10 minutes or by running them through a dishwasher cycle. Once your jars are sterilized, you can start filling them with your blackberry jelly.
3. Using a funnel and a ladle, pour the hot jelly mixture into sterilized Mason jars, leaving about 1/4 inch of headspace. You can easily measure the head space with this canning funnel.
4. Wipe the rims of the jars with a dampened clean paper towel to remove any residue. Place the sterilized metal canning lids on the jars and screw on the rings.
5. Place the jars in a water bath canning pot and cover them with boiling water. Fill the canner with enough water to cover the jars by at least 1 inch. Boil pints for 10 minutes or half pints for 5 minutes.
6. Remove the jars from the pot and let them cool on a towel for 24 hours. This allows the jelly to set properly.