Pick your berries. These blackberries are from our back yard. It took about two weeks to get 8 cups of blackberries. We picked them every morning and evening, put them in a gallon size ziploc bag and froze them until we had enough to make the jam.
Wash your berries well and drain them. The blackberries were covered in bugs, fruit flies and ants.
Cook the berries on low heat and mash them with a potato masher them. It's much easier to deseed them if they're mushed.
Deseed your blackberries in a Stainless Steel Food Mill.
You will end up with about 6 cups of blackberry syrup. Pour it in a large pot, add the sugar and pectin and cook on medium high for 5-10 minutes. Let stand for 5 minutes.
Pour the jam in sterizied half-pint mason jars and put the lids and rings on them.
Process the jars in a boiling water bath for 10 minutes.
Remove and cool the jars in a draft-free place overnight. Enjoy!