• Prepare your boiling water canner for a water bath method. Put the canning rack at the bottom of a large pot and heat the jars in simmering water until it's time to use them. Wash the lids in warm soapy water and set aside until ready for use.
• Mix the calcium water as per Pomona's Pectin instructions.
• Rinse the blackberries and mash them in a large bowl (a potato masher works well).
• Measure 4 cups of mashed blackberries (saving any extra for another use) and put in a saucepan. Add the lemon juice and calcium water and mix well.
• In a small bowl, combine the sugar and pectin powder and mix thoroughly.
• Bring the blackberry mixture to a full boil over high heat, then slowly add the sugar-pectin mixture, stirring constantly.
• Continue to stir vigorously for 1 to 2 minutes to dissolve the pectin as the jam comes back up to a boil. Once the jam returns to a full boil, remove it from the heat.
• Use a jar lifter to place the jars onto a wooden cutting board or kitchen towel and ladle the hot jam into the funnel to pour the jam into the prepared jars. Leave about 1/4 inch of headspace and remove any air bubbles.
• Wipe the rims of the jam jars and center a lid onto each jar and apply the band, adjusting to fingertip tight. Place the filled jars into the boiling water canner, making sure there is 1-2 inches of water covering the jars.
• Process the jars in a boiling water bath for 10 minutes. Turn off the heat, remove the pot lid, and let the jars sit inside for 5 minutes.
• Use a jar lifter to remove the hot jars and let them cool for 12 to 24 hours. Check to make sure the lids are all sealed, they should not flex when the center is pressed.

To Make No-Sugar Blackberry Jam

• Replace the sugar with ¾ cup water or juice (apple juice works well).
• Bring the water/juice to a boil and then put it into a blender or food processor with the pectin powder and vent the lid.
• Blend for 1-2 minutes until all of the powder is dissolved.
• Add this mixture instead of the sugar-pectin mixture to the boiling blackberries in Step 6 of the recipe above.