Optional: add a teaspoon of butter or margarine to reduce foaming.
Cover, bring to a boil over high heat, then lower to a simmer, covered for 2 to 4 minutes stirring frequently.
Remove from heat, mash right in the pot.
Transfer to cheese cloth or a jelly bag and suspend over a bowl or large jug for about 2 hours to let juice drip off.
You want to end up with about 1 litre (4 cups / 32 oz) of strawberry juice.
You can freeze the pulp for another use including adding to batches of jam or pie fillings.
LIQUID SWEETENERS (HONEY, AGAVE, LIQUID STEVIA, ETC): See special directions below before proceeding further.
DRY SWEETENERS (SUGAR, SPLENDA, POWDERED STEVIA, ETC): Mix the pectin powder with the sugar in a small bowl or a measuring cup, set aside. Add the calcium water to the pot. Bring pot contents to a boil, then add pectin mixture.
ALL SWEETENERS: Add balsamic vinegar to mixture in pot. When pot returns to a boil, let boil for 2 minutes, stirring constantly.
Remove from heat.
Ladle into 125 ml (4 oz) or ¼ litre (½ US pint / 8 oz) jars.
Leave 1 cm ( ¼ inch) headspace.
Debubble, adjust headspace if needed.
Wipe jar rims.
Put lids on.
Process in a water bath or steam canner.
Process jars for 10 minutes; increase time as needed for your altitude.
Notes
You can start with frozen, thawed berries. If so, don't discard the juice from the berries as they thaw, add it in.Pomona pectin comes with a small pouch of powdered calcium for you to mix with water to make calcium water.The pectin powder will clump if you just mix it straight into the fruit; that's why you mix it with something first.If you use liquid stevia, how much you need will depend on the tastes of your crowd and how sweet / tart that particular batch of blueberries was. Normally, 1 teaspoon is sweet, 2 is very sweet.