Remove stems and blossom ends from crab apples, and cut into quarters. Place them in a large stainless steel or other non-reactive pot or saucepan. Add enough water to be able to see, but no so much that the crab apples are floating. Bring to a boil, reduce heat to medium, and let simmer for 10 to 15 minutes. The apples should soften and change color.

Strain the apples and juice through 2 or 3 layers of cheese cloth. Do not squeeze. Use just the clear juice. You should have at least 4 cups of juice. Discard pulp, and pour the juice back into the rinsed pan. Bring to a simmer, and let cook for 10 minutes. Skim off any foam that comes to the top. Next, stir in the sugar until completely dissolved. Continue cooking at a low boil until the temperature reaches 220 to 222 degrees F (108 to 110 C). Remove from heat.

Pour the jelly into sterile jars leaving 1/4 inch headspace. Process in a hot water bath to seal.