Remove stem and blossom ends from washed crab apples, cut in halves and place in large kettle. (Red fruit makes the most colorful jelly.) Add water and cook until fruit is very soft, about 10 minutes.
Strain mixture through jelly bag, but do not force juice through bag.
Measure juice. You should have about 7 c. Stir in ¾ c. sugar for every cup of juice.