Examine each canning jar to make sure that they are in good condition and have no cracks throughout the jar and/or chips on the rim of the jar.
Place a rack at the bottom of the water bath canner and fill the canner 3/4 way full with water. Place 6-7 quart-sized canning jars into the canner. The jars should be submerged in the water.
Turn on the heat to bring water in the canner to a simmer. Allow the jars to simmer in hot water until they are ready to be filled.
Fill a large stock pot with water halfway full, and add 2 tablespoons of lemon juice.
Add halved or sliced pears to the large stock pot as you are peeling and halving or slicing them. (This will prevent them from browning.) Once finished, bring the water and pears to a boil. Once the water boils, immediately turn the heat down to a simmer, and simmer the halved or sliced pears for 5 minutes before removing the stock pot from the heat.
Remove one jar at a time from the canner. Empty out any hot water that might be in the jar back into the canner. Be careful. The water will be hot.
Place the jar on a cushioned surface, such as a double-folded dish towel or cushioned drying mat. Next, place a funnel over the opening of the jar and pack the jar with pears. Leave a half-inch headspace from the rim of the jar.
Add 2 tablespoons of bottled lemon juice to the jar.
Next, fill the jar with the cooking liquid from the stock pot, leaving a half-inch headspace from the rim of the jar. This liquid will help to fill in the empty space in the jar.
Use the de-bubbler tool to make sure you have released all bubbles from the jar. If the jar drops below a half-inch headspace after you have de-bubbled the jar, top off the jar with additional cooking liquid. (See video.)
Clean the rim of the jar with a paper towel or clean rag that you have dipped in white vinegar.
Place a new clean lid on the jar.
Place a band (ring) on the jar and tighten it to fingertip tight. (See video.)
Using a jar lifter, carefully place the jar on the rack in the water bath canner.
Proceed filling remaining jars until all the jars are full and placed into the canner.
After you have finished filling and placing the jars into the canner, add additional water, if needed, to cover the top of the jars by at least one inch. Place the lid on the water bath canner and bring the water to a boil.
Once the water in the canner comes to a boil, start your timer. Boil quart-sized jars for 25 minutes. Depending on your altitude, or if you are using pint-sized jars, you may need to adjust your timing. (See RECIPE NOTES below.)
After boiling canned pears for 25 minutes, turn off the canner and carefully remove the lid. Open the lid away from you as there will be a significant release of steam from the canner.
Allow jars to rest in the canner for five minutes.
After five minutes, remove the jars from the canner, one at a time, using the jar lifter. Place the jars on a cushioned surface.
Allow the jars to cool at room temperature for 12-24 hours. After 12-24 hours, make sure that all the jars have sealed successfully by examining the lids. The "button" in the middle of the canning lid should be depressed (indented). (See video.)
If all seals are successful, remove the rings and store the jars in the pantry. If any seal is not successful, refrigerate the jar immediately.