Have ready hot, sterilized jars and their lids (see page 228). Place 2 or 3 small plates in the freezer.
In a large nonreactive saucepan over medium-high heat, bring the pomegranate juice to a boil. Add the pectin and return to a boil. Cook, uncovered, stirring frequently, until the liquid is reduced by one-third if using fresh pomegranate juice, and by half if using purchased pomegranate juice.
Stir in the sugar, bring to a boil, and cook, stirring frequently, until the jelly is thick enough to sheet off the back of a spoon, about 1 minute. Remove from the heat. Use 1 tsp jelly and a chilled plate to test if the jelly is ready (see page 231).
Ladle the hot jelly into the jars, leaving 1/4 inch of headspace. Remove any air bubbles and adjust the headspace, if necessary. Wipe the rims clean and seal tightly with the lids.
Process the jars for 10 minutes in a boiling-water bath (for detailed instructions, including cooling and testing seals, see pages 228–229). The sealed jars can be stored in a cool, dark place for up to 1 year. If a seal has failed, store the jar in the refrigerator for up to 1 month.
This pomegranate jelly recipe is reprinted with permission from <a href="http://www.weldonowen.com/food-drink/baking-desserts/art-preserving">The Art of Preserving</a> by Lisa Atwood, Rebecca Courchesne, Rick Field and published by Weldon Owen.