Steps

1. Combine the juice and sugar in a wide, heavy-bottomed, nonreactive pan (that is, a pan with a stainless-steel or well-enameled interior surface). Place the pan over medium heat. Stir until the sugar is dissolved, and then raise the heat to medium high.
2. Boil the syrup, skimming occasionally, until it begins to jell. This will take only a few minutes. You can test for jelling by scooping a little of the syrup with a metal spoon and then tipping the spoon high over the pan. You’ll see the drops thicken and slow, and then two drops will run together. That’s the point at which you remove the pan from the heat.
3. Skim any remaining foam from the surface of the syrup. Immediately pour the syrup into three sterilized half-pint mason jars. Add the jar lids and rings, and process the jars in a boiling-water bath for five minutes.
4. Remove the jars from the water bath, and let them cool on a rack or pad. Leave them alone until the next day, when the jelly should be firm.