Prepare the calcium water from the Pomona package. Put 1/2 teaspoon calcium powder (the small packet) and 1/2 cup water in a small jar with a lid. Set aside. Shake well before using.
Fill your water bath canner to a level that will cover your jars. This varies depending upon jar size. Heat water to boiling, while proceeding with next steps.
Wash and rinse jars. Bring lids and rings to a boil; turn off heat and let stand in hot water.
Finely chop the tangerines. I cheated and used a food processor. Much faster, if you have one. Put chopped tangerines, tangerine, juice, ginger juice, and 2 tablespoons of the calcium water into a large stock pot.
Measure 6 cups sugar into a separate bowl. Thoroughly (and I mean thoroughly) mix in 3 tablespoons of pectin (the large packet from Pomona).
Bring tangerines and juice to a boil, stirring frequently. Add sugar mixture and stir vigorously for a couple of minutes to dissolve the pectin. Return to a boil and then remove from heat.
Stir in vanilla.
Fill jars to within 1/4″ of top. Wipe rims clean with a damp cloth. Screw on 2-piece lids/rings and place in boiling water bath. Bring water back to a boil (it doesn’t need to be a hard boil) and set the timer for 10 minutes. Remove jars to a towel-covered counter top to cool.
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).
10. Remove rings and wash outsides of jars. (You don’t need to store the jars with rings.)