Sterilize jars by simmering them in boiling water for 10 minutes. Wash bands and lids.
Core, peel and chop pears. Measure 4 cups of prepare pears and add to a large saucepan with the lemon juice.
In a separate boil measure the 5 cups of sugar and set aside for later.
Stir in the packet of Sure-Jell into the pear mixture.
Bring the pear mixture to a full rolling boil. This is a boil that doesn’t stop bubbling when stirred. Be sure to stir constantly.
Once the pear mixture is to a full rolling boil, add the sugar. Return to a full rolling boil and boil 1 minute. While stirring constantly.
Ladle the jam into the sterilized jars to within 1/4 inch of the top of the jar. Wipe the jar rims and threads clean.
Place lid and bands on jars.
Process 10 minutes in a boiling water canner or adjust for altitude. You can find more information here about extending time for altitude and the full canning process to follow for jams and jellies in the notes section below.
Once processing time is done, remove jars and let cool on a towel.
Test to make sure jars are sealed once cooled. If the jar lid is not sealed refrigerate the jam.
Properly processed and sealed jars can be stored at room temperature for up to 1 year.