Carefully wash blueberries in cold water, working with a quart or two of berries at time. Drain the berries, removing any spoiled berries, stems, and leaves as you work.

Prepare a water bath canner or pressure canner, jars, and two-piece lids.

To prepare extra light syrup, combine sugar and sugar in a large stockpot in the amounts called for below. For a sweeter syrup refer to the table listed in the notes; blueberry syrup, fruit juice, and water may be substituted.

Bring the canning liquid to a boil. Carefully ladle 1/2 cup of hot syrup/canning liquid into each prepared jar.

For a raw pack: Fill each jar with blueberries, gently shaking the blueberries so they fill the jar out evenly. Cover the berries with hot syrup, leaving 1/2-inch headspace between the top of the liquid and the bottom of the lid. Wipe the outside of the jars clean. Apply and adjust the lids until fingertight. Load into a water bath canner and process for 15 minutes (pints and quarts). For canning times at higher altitudes, or if you're using a pressure canner, see the notes section below.

For a hot pack: Bring a large pot of water to boil. When the water is boiling, immerse the blueberries in the water. Wait until the water is boiling again before setting a timer for 30 seconds. Drain the berries when the time is up. Fill prepared jars with blanched blueberries and cover with hot syrup or other canning liquid, leaving 1/2-inch headspace between the liquid and the lid. Wipe the outside of the jars clean. Apply and adjust the lids until fingertight. Load into a water bath canner and process for 15 minutes (pints) or 20 minutes (quarts). For canning times at higher altitudes, or if you're using a pressure canner, see the notes below.

Allow the processed jars to sit in the hot water bath canner for 5 minutes before removing with a jar lifter. If using a pressure canner, turn off the heat and let the water come to room temperature (and the pressure to 0) before removing the jars.

Set the jars on a clean towel or drying rack, making sure there's at least one inch of space around each jar. Let the jars sit for 24 hours before checking the seal on each lid (refrigerate any jar without a proper seal), label, and store in a cool, dark, dry place for up to 18 months.