Recipe yields 10 half-pint jars.

Prepare for Canning

• Prepare the calcium water: Combine ½ teaspoon calcium powder (from the small packet in the box of Pomona’s pectin) with ½ cup water in a small jar. Screw on a lit and shake until well-combined. You'll have more than you need for this recipe. Store the excess in the refrigerator for use in making additional jam or jelly recipes.
• Wash the jars you'll use, making sure each is clean and free of nicks in the rim, which could impede sealing.
• Wash the lids and rings in hot soapy water. (If you're using non-Ball brand lids, prepare as suggested by manufacturer.)
• Place empty jars in a canning pot or large stock pot with enough water to cover by an inch or two, cover pot, and set on high heat. It can take awhile for the water to heat, so get it started before you begin making the recipe.

Make the preserves

• Wash and dry the pears and dice enough unpeeled pears into 1/2” pieces to make 2 cups; set aside. 
  8 - 9 pounds pears
• Cut remaining fruit into pear chunks and mash coarsely with a potato masher until you have 6 cups; transfer to a large pot. Combine pears with the ginger, prepared calcium water, and lemon juice; stir to combine well.
  2 tablespoons ginger root, 8 teaspoons calcium water, 1/2 cup lemon juice
• In a separate bowl, combine the sugar with the pectin powder (the large envelope) until thoroughly combined.
  1 cup sugar, 6 teaspoons pectin powder
• Bring mashed pears to a full boil. Add sugar mixture, stirring vigorously for a couple of minutes to dissolve the pectin. Stir in diced pears. Return to a full boil, boil for one minute, and remove from heat.

Canning pear preserves

• Lift empty jars from the boiling water canner and drain. Ladle hot mixture into half-pint jars to within aquarter inch of the rim. A canning funnel makes this easy.
• Wipe rims of jars to remove any of the preserves that may have spilled. A clean rim is essential to a good seal.
• Set jar lids in place. Screw bands on finger tight.
• Use a jar lifter to gently submerge jars into the hot water bath. Be sure to place a wire rack in the bottom of the pot to prevent the jars of pear jam from sitting directly on the bottom. There should be enough water in the canner to cover the top of the jars by an inch or two. The water will cool somewhat in reaction to the addition of the jars. Return the water to a low boil and then set the timer.
• Process in a boiling water bath for 10 minutes. Add a minute to the boiling time for every 1,000' above sea level. Lift jars from the canner and place jars on a kitchen towel on the counter.
• Check seals. Lids should be solid and pulled down tight. (if they flex and pop, the jar didn’t seal; put unsealed jars in the refrigerator and use those first).
• Remove rings and wash outsides of jars. Store in a cool, dry place.