Blackcurrant - stopped working?

[hotezenwald]

What is SG? Have been playing with garden drinks but can't find any simple good books in English or German here in Germany. Bought myself the measures for sugar (for apple juice Most) which we barrel and drink over a year or so and cos it tastes rather potent after half a year also bought an alcohol measure but no info included how to use either. Can you recommend a good book which I can buy from Amazon?

[Headfry]

CJJ Berry wine making book is good, most here in UK tend to refer to this.
SG = specific gravity and is the ratio of the density of a substance to that of water.