Prepare Jars: Examine all jars for cracks or chips and discard any damaged jars. Wash jars and rings in hot soapy water, rinse thoroughly, and keep jars hot in a 180°F oven or hot water until ready to fill.
Heat Lids and Syrup: Place new canning lids in a small saucepan with hot water at 180°F and keep hot until ready to use. In another pot, combine sugar and water for syrup, bring to a boil, and keep hot throughout packing process.
Prepare Canner: Fill your boiling water bath canner with enough water to cover jars by 1-2 inches when submerged. Begin heating water to a rolling boil while preparing peaches.
Blanch and Peel Peaches: Wash peaches and score an X on the bottom of each fruit. Blanch peaches in boiling water for 30-60 seconds, then immediately plunge into ice water. Remove skins by slipping them off with your hands or a knife.
Slice and Treat Peaches: Cut peeled peaches in half, remove pits, and slice into uniform pieces about 1/2 inch thick. Immediately place sliced peaches in water treated with ascorbic acid or lemon juice to prevent browning while you work.
Hot Pack Method: Drain treated peaches and place in a large pot with hot syrup or water. Bring to a boil and boil gently for 5 minutes, stirring carefully to heat fruit evenly without breaking slices.
Fill Jars: Using a slotted spoon, pack hot peaches into hot jars, leaving 1/2 inch headspace. Cover with boiling syrup or water, maintaining the 1/2 inch headspace and ensuring liquid covers fruit completely.
Remove Air Bubbles: Run a plastic bubble removal tool around the inside of each jar to release trapped air bubbles, adjusting liquid level as needed to maintain proper headspace. Wipe jar rims thoroughly with a clean, damp cloth.
Seal Jars: Center hot lids on jars and apply rings finger-tight only. Using jar lifter, place filled jars on canner rack, ensuring jars do not touch each other or the sides of the canner.
Process in Water Bath: Lower jars into boiling water, ensuring they are covered by 1-2 inches of water. Process pint jars for 25 minutes or quart jars for 30 minutes, adjusting for altitude: add 5 minutes for 1,001-3,000 feet, add 10 minutes for 3,001-6,000 feet, add 15 minutes for above 6,000 feet. Remove jars and cool undisturbed on a towel for 12-24 hours.
