Boil a runny syrup with from the sugar and water. Grate the peeled quinces directly into the boiling syrup using a coarse grater. Press the grated quinces with a spoon in the syrup, so they do not darken.
Once all quinces are in, mix well and optionally add 2 cloves. Boil on a strong stove and once thickened, add the citric acid. 3-4 minutes later, remove the jam from the heat and pour it in jars that are capped and sterilized for a few minutes.