1. Peel, core pears. Start the jam by selecting and washing pears that are fully ripe. Peel the pears with a small paring knife or vegetable peeler. Cut the peeled pears into quarters. Use a paring knife to cut out the cores. Cut the pears into large pieces and place them in a large mixing bowl.
2. Mash pears and raspberries. Use a potato masher or fork to break the pears into small pieces. Measure the pears. You should have 2-1/2 cups of mashed pears. Place the raspberries in another bowl and mash into small pieces.
3. Add sugar to boiling fruit mixture. Measure the sugar and set it aside until you need it. Use a 6- or 8-quart Dutch oven or kettle to make the jam. You need a large pan so the mixture can come to a full rolling boil without going over the sides of the pan. Combine the mashed pears and raspberries, the lemon juice, and the powdered fruit pectin in the Dutch oven. Bring to boiling over high heat, stirring constantly. Stir in the sugar. Bring to a full rolling boil. A full rolling boil is one that cannot be stirred down. Boil the mixture hard for 1 minute, stirring constantly, using a long-handled wooden spoon. Remove the Dutch oven from the heat. Use a metal spoon to skim off the foam.
4. Fill jars, seal, and place in water-bath canner. To fill the jars, place a wide-mouth plastic funnel in a sterilized, hot half-pint canning jar. Ladle the jam into the hot jar, leaving 1/4-inch of space at the top of the jar. Remove the funnel and wipe the jar rim with a clean, damp paper towel. Food on the rim prevents a perfect seal. Position a prepared lid and screw band on the jar and tighten according to the manufacturer's directions. As you fill each jar, place it in the canner. The jars should not touch one another. Cover the canner. Begin the processing time when the water returns to boiling. Process the jam for 5 minutes in a water-bath canner. Remove jars from canner and cool on a wire rack.
5. Makes 8 half-pints.
6. Test seals, store, and serve. When the jars have cooled, press the center of each lid to check the seal. If the dip in the lid holds, the jar is sealed. If the lid bounces up and down, the jar isn't sealed. If you have a jar that has not sealed, you can store the jam in the refrigerator for up to 3 weeks. Label the sealed jars with the content and date. Store in a cool, dry place for 1 year.