Soak young green beans in very salty water for several days until they turn yellow. Transfer them to a clean vessel and cover with strong, hot vinegar. Pour off this vinegar the next day, bring the vinegar to a boil, and repour over the beans while still hot. Repeat this process on the third and fourth days, that is, until the beans regain their natural color. For the last boiling, add a bay leaf and allspice to the vinegar.