Clean the washed sour cherries from their stems. For every 2 lb (1 kg) of cherries, put 4 1/5 cups (1 liter) of water in. Boil them. Strain.
Add the sugar to the strained juice: every 4 1/5 cups (1 liter) of juice needs to get 2 lb (1 kg) of sugar. Boil the mixture until it begins to thicken and 5 minutes before removing it from the heat, add the citric acid. Constantly remove the foam from the top.
Distribute the hot syrup into warmed bottles, close with caps and turn the bottles upside down until they cool. For longer storage, you can sterilize them for 10 minutes.