Mix the water with the citric acid in a large bowl. Only remove the coarse stems from the elderflower, do not wash and add to the citric acid water. Let it steep for 24 - 36 hours, stir once if necessary.
After the steeping time, filter the brew through a dense tea towel that is placed in a household sieve. Any animals that may be present also remain in it.
Measure 900 ml of this filtrate and place in a sufficiently large saucepan. Add the preserving sugar and bring to the boil while stirring. Let it simmer for at least 3 minutes - see also instructions on the package.
Then immediately pour into jars rinsed with hot water and close tightly. I don`t put the jars on the lid so that nothing spills out - the vacuum forms by itself when it cools.
The jelly tastes slightly tart and bitter like elderflower and nothing else.