Select large, ripe, completely firm rose hips. If they are even a little soft, they are unsuitable. Clean them out carefully so that the slits are small. Place them in a basin and bring them to a boil several times in a juice prepared from cranberries or red currants (boiled in water until the berries whiten). Bring the rose hips to a boil 2–3 times in this juice without letting them soften at all, just long enough so that they are not completely raw. Turn them into a sieve to let the juice drain off. When they have cooled completely, pack them into a jar and pour over them some of the same vinegar used for marinating white plums.