- 1¼ pounds blueberries
- 3 cups sugar
- Zest of 1 lemon
- 1½ teaspoons pectin
- Place a small ceramic or glass plate in the freezer. Place the blueberries in a large bowl and mash with 2¾ cups of the sugar and the lemon zest. Transfer the mixture to a medium saucepan and cook over medium heat until the juices simmer, 3 to 4 minutes, stirring often.
- Meanwhile, mix the pectin with the remaining ¼ cup of sugar. Add the pectin mixture to the blueberries and continue to cook until the mixture reaches 220°F to 222°F, another 30 to 35 minutes (note that the jam will stay at around 217°F for what seems like an eternity-be patient, the temperature will rise, so stick with it), skimming the foam from the top and stirring every so often. Take the plate out of the freezer and spoon a small dollop of jam onto it. The jam should set up semi-stiff, and when you run your finger through it, the trail should not run back together immediately. If it does, keep cooking. If it doesn’t, turn off the heat and let the jam sit for 10 minutes. (This helps ensure that your berries don’t float to the top of the jam jar.)
- Fill a large stockpot or canning pot with water and bring to a boil. Add the jars, lids, and bands, and simmer for 5 minutes. Use tongs to remove the jars, bands, and lids to a clean kitchen towel. Once cool enough to handle (but still warm) fill the jars nearly full with blueberry jam, leaving a ½-inch space at the top. Screw the lids on.
- Add more water to the pot if necessary and bring to a boil. Place a canning rack in the pot and set the filled jars into the rack. Boil the jars for 10 minutes (the filled jars should be completely covered by the boiling water). Using tongs, remove the jars and place on the kitchen towel. If refrigerating, be sure to cool the filled jars for at least a few hours first. Unopened, the jam will keep in a cool, dark place for a few months. After opening, try to eat the jam within a week or two (not that it will last that long!).