Place the currants in a deep saucepan. Add a glass of water. Bring to a boil over low heat. Remove from heat and cool. Rub the berries through a sieve into the saucepan. Pour in the sugar and stir. Put the saucepan on low heat. Wait until the currants boil. Do not cover with a lid. Cook for 30 minutes.
Transfer the mixture into jars. Roll up. When the jelly has cooled, put it in a cool place.