I run two different batches of preserves; one is the standard jam that we all love, the other is syrup consistency. Syrup is awesome for quick sauces, vinaigrettes, and most certainly juice. I love cherry juice, I mix a cup size of syrup preserve on a quart jar with water and a bit of sugar (plus a few drops of almond extract).
If you like currant juice this is one of the most convenient ways to preserve it.
only difference i do is i add the sugar before storing. once i get enough cherries i plan to do the same.
I remove the seeds from my blackberries too.
I got one of these attachments for my Kitchenaid mixer off of Ebay. New old stock. I donāt think they are made anymore. A fried swore they are perfect for removing blackberry seeds for jam. It didnāt work well for me with raw fruit. Havenāt tried it with cooked yet: