Wine made with fruit or grape juice: Decide how much alcohol your wine is going to have: for light wine 9-12, or strong wine 17%. Calculate the percentage of alcohol x litres x 17 grammes sugar. Deduct the amount of sugar already in the juice. Add the difference.
Determine the sugar content of the juice or must. Degress Brix = % sugar, thick dilute a little juice in the same proportions in a measuring glass. The hydrometer reading x 2 grammes of sugar in the juice.
Proceed as follows: You are making 20 litres of wine with an alcohol strength of 11%. 20 x 11% x 17 grammes of sugar is 3.740 grammes. You use 5 kg of grape juice containing 650 grammes of sugar. There thus remains 490 grammes of sugar to add before fermentation. Ferment out the wine (too dry), then add sugar for the taste and body.
Alternatively: You have 20 litres of juice and wish to produce 20 litres of wine with 10% alcohol. You want a residual sugar level of 0 degrees on the hydrometer. Dilute the juice in the same proportion as the entire batch is to be diluted, 1 + 3 (50 ml + 150 ml = 2 dl) which when measured shows a +70 degrees hydrometer (with Oechslescale) reading. You need a reading of 80 degrees to achieve 10% alcohol to 0 degrees, so you are short by 10 degrees. 10 degrees x 2.7 grammes sugar x 20 litres = dissolve 540 grammes of sugar directly in the must.
If you are using dried fruit, it does not often contain much sugar. If using the tables in the book “Home Winemaking” consider the dried fruit as being sugar free. Note that the added sugar must be dissolved (in water or must) before it will ferment.