I also did the Blackberry this summer. We, the wife and I, picked for about three weeks, freezing as we went along. We had somewhere around 35 to 40 lbsof berries.( A very good year for berries here just east of St. Louis)I took about 30 lbs and rendered down the juice in a big stock pot on the stove. then took the juice, about 4 gal. and started from there.Did the usual chems, sugar, etc.(without adding any acid). I let it ferment down to 1.0. racked off added waterto about 5gal. batch and stopped the fermintation. Pretty dry at this stage. Then I used the rest of the Blackberries, about 15 lbs., to make a F-pack. This consisted of the Blackberries and 4 lbs. of sugar cooked on the stove. This helped the flavor tremendously. Then added lite-toast american oak, 6 to 8 oz. and topped up to the neckof the carboy and let it age for three months before bottling. I back sweetened and left it a little tart with a hint of the oak and ummm-ummm-ummm
The wife says it's a little too tart but I feel that a true Blackberry taste is tart. To each his own I guess
The wife and her best friend made a Peach-Apricot this summer. WOW!! And now are in the process of making an Apple-Pear. Oh, the possibilities are endless!!!!! MY next project will be a Concord from scratch. WOOHOO!!! And I might even fortify it.