2 quarts fresh blackberries (1/4 of which are unripe)
6 cups granulated sugar
Wash berries and cook in saucepan over moderate heat until juice begins to flow and berries are soft. Run through a food mill to obtain juice and pulp. Measure out 4 cups of juice and pulp mixture and place in preserving pot. Bring to a boil. Add sugar and cook over moderate heat until candy thermometer reaches about 220 degrees F (about 30 minutes).
Pour into jars and seal. Extra juice and pulp may be kept in refrigerator for 2 weeks or frozen for making another batch of jam later.
Yields 6 half pints.