I tried this recipe and it didn’t set properly, but it was also my first attempt at jam. I’ve added it here more for my own record with specific notes for next time.

3 pounds fresh peaches (4 cups crushed; this was about 7 medium-sized peaches)
1 package powdered pectin (approximately 1.75 ounces)
2 tablespoons lemon juice
5 cups sugar
1/2 teaspoon cinnamon
1/2 teaspoon allspice (the original recipe calls for just cinnamon OR allspice but that’s no fun, is it?)

Sort and wash fully ripe peaches. Remove stems, skins, bruises and pits. Crush peaches. 
(I tried parboiling the peaches to remove the skins but this was easier on the farmer’s market peaches than the store-bought ones, using a mix of both. The riper the peaches, the easier this whole thing will be — and BE SURE TO REALLY CRUSH THE PEACHES. They will not have enough time on the stove to cook down in this recipe.)

Measure crushed peaches into a large pot. Add lemon juice and pectin; stir well. Place on high heat and, while stirring constantly, bring to a full rolling boil with bubbles over the entire surface. Add the sugar and spices all at once and heat again to a full bubbling boil. Boil hard for 1 minute (set a timer), stirring constantly. (It seemed too weird to bring solid peaches to a boil with such a scant amount of liquid and a dry powder, so I made the mistake of adding the sugar early and this was apparently a mistake.)

Remove from heat; skim foam off the top. (This can be saved in the refrigerator and enjoyed on toast. I love it warm straight off the stove as well! The foam is like a peach butter and quite tasty.)

Pour immediately into sterile canning jars. Fill the jars to 1/4 inch from the top. Seal them and process for five minutes in a boiling water bath.