In a large saucepan, combine quince and water. Bring to the boil, then reduce heat and simmer with lid on for about 1 hour or until quince is soft.
Strain mixture through fine cloth and stand overnight. Allow liquid to drip through cloth slowly, do not squeeze cloth. Discard pulp (or save and use it to make quince paste).
Measure quince liquid. Use 1 cup (220g) of sugar for each cup (250ml) of quince liquid.
Combine quince liquid and sugar in a large saucepan. Stir over heat, without boiling, until sugar is dissolved. Stir in juice, and bring to the boil. Boil with lid off, without stirring, for 25 minutes or until jelly sets when tested on a cold saucer.
Pour jelly into hot sterilised jars; seal while hot.