Wash and clean the blackcurrants well. Pour them into a wide and deep container and mash them.
Pour in about 7 cups (1.7 L) water, stir and leave to sit as is for 3 hours. Then put it to strain through a gauze overnight.
The next day, measure the quantity of juice released and add 3.5 lb (1.5 kg) sugar for every 4 1/5 cups (1 L) juice. Add the citric acid and ground to powder aspirin.
Stir and let it sit for 7 hours. Stir periodically, so the sugar dissolves completely.
Then distribute the blackcurrant syrup into bottles, close them and sterilize for 5 min.