OK, this took me a little longer to get round to as it wasn't just a matter of editing my previous post with the quantity of sugar used. Top tip: If your method of separating juice from fruit pulp involves hanging a jelly bag up by a piece of string, maybe think twice about processing eleven pounds of fruit in one go.
There was a lot of cleaning up to do after that. There were even splashes of blackcurrant juice on the ceiling.
At this point I remembered that I do actually have a small wine press in a cupboard in the store room. Although missing a tube to convey juice into a container, it does have one very useful feature: A splash guard. You might well ask why I didn't use this in the first place. So might I.
I can't tell you how much juice I extracted from my 11 lb 4 oz of fruit because I didn't measure it before I added the sugar. I stirred in 1 kg sugar, which tasted about right, then bottled it. The final count comes to 3 ½ litres of cordial, most of which is now in the freezer, because I don't add enough sugar to act as a preservative.
Speaking of sugar, and because we were talking about the anti sugar campaign recently, I thought I'd work out the sugar content per drink. It's a fairly strong cordial, so a suitable dilution is about one in ten, making a total of 35 litres of made up drink. One drink is about 250 ml, so that's 140 drinks in total. One kilo of sugar divided by 140 drinks is 7.1 g added sugar per drink. Blackcurrants contain about 6% sugar so... oh, I'm going to have to convert units to do this bit... 11 lb 4 oz is 5.1 kg, 6% of 5.1 kg is 307 g, divided by 140 drinks, is 2.2 g per drink. If I managed to extract all the sugar from the currents, that's a total of 9.3 g sugar per drink, or 3.7 g per 100g. I include that last measure for comparison with a recent survey of commercial soft drinks.