Sort and wash the weighed blackberries. Put in a saucepan and crush with a potato masher. Add the water, bring to the boil and simmer for about 15 minutes.
Filter the pulp through a cloth. The juice obtained is weighed or measured and mixed with the sugar. For 1 kg (1 liter) of juice you calculate 750 - 1000 g of sugar.
Bring the juice with the sugar to a boil over high heat and then skim it off. Stir the canning aid into the juice that is no longer boiling. Fill the hot juice into bottles and close after cooling.