Ok...here's my 'old fashioned mom recipe' for blackberry jam.

8 Cups of blackberries (whole)
5-6 Cups sugar

1/2 C lemon juice

Fill the sink with lots of cold water, dump in the berries. Swish them around carefully. Repeat. Put the cleaned and rinshed berries in a big pot, add sugar and lemon juice and turn the heat on!! LOL (You wont need to add water, because there was enough water on the berries from rinsing)
I cook these on a medium to medium high heat bringing them to a rolling/simmering boil you can stir away till they start to thicken and coat the back of a spoon good. Usually about 45 minutes. (the juice and the water will reduce some) Get your jars ready! It'll take about 9-10 1/2 pint jars. Ladle the jam into the jars wipe off the rims good, put on the lids. I turn my jars upside down at this point, for about 15 minutes while I'm cleaning up (cuz it gets the lids hot) then turn them right side up and wait and listen for the glorious 'pop' as each one seals. I do have a secret ingredient, that is an optional one, but it's good added to ANY jam. When the jam begins to cook it will 'foam'. I do remove SOME of the foam, but not all. At this point, I add 2 Tablespoons of butter. (REAL BUTTER..no marg!)
This takes away the foam and makes the jams just taste..rich I guess. It was something I saw my mom do for years. I've done it every since I started making jams.
No, I don't use fruit pectin. I figure, they didn't way back when, why should I now?