This question is relating to cider making but it will probably apply to wines as well.
I am following a Youtube video on making a gallon of scrumpi using 4L apple juice and 340 gms of sugar. The recipe says to hold back on the 4th carton of apple juice as the fermentation is usually vigorous and will usually fill the airlock etc and to add the last carton when it subsides. Now the problem, how to you work out the starting gravity. If you measure right at the start with only 3L of apple juice the reading wont be the same as if you had the full 4L in. If you measure after adding the 4th carton then that wont represent the true starting SG as quite a chunk of fermentation has already taken place. I have looked for a formula or guide to estimate what the starting gravity should be without much luck.
I am following a Youtube video on making a gallon of scrumpi using 4L apple juice and 340 gms of sugar. The recipe says to hold back on the 4th carton of apple juice as the fermentation is usually vigorous and will usually fill the airlock etc and to add the last carton when it subsides. Now the problem, how to you work out the starting gravity. If you measure right at the start with only 3L of apple juice the reading wont be the same as if you had the full 4L in. If you measure after adding the 4th carton then that wont represent the true starting SG as quite a chunk of fermentation has already taken place. I have looked for a formula or guide to estimate what the starting gravity should be without much luck.