Set 2 - 3 large spoons in the freezer (this will help you test the consistency of the jam later).

Place berries in a large Dutch over or other non-reactive pot set over medium-high heat. Add two cups sugar and lemon zest. As berries cook, mash about half the berries with a spoon. Once mixture starts to bubble vigorously, turn heat down to medium, so that it bubbles gently, and cook, stirring often, for 5 minutes.

Meanwhile, combine powdered pectin and remaining 2 tablespoons sugar.

Stir calcium water into the jam, and bring mixture back up to a boil. Stirring vigorously, gradually sprinkle in the pectin sugar mixture and cook for 5 minutes (the combination of boiling and sprinkling helps prevent pectin clumps). Remove jam from heat and stir in balsamic vinegar.

Add about 1 teaspoon of jam to a frozen spoon. If it wrinkles up when you push it with your finger, it's ready. If it still seems too runny, cook for 5 more minutes, then test again.

Ladle jam into sterilized jars, leaving 1/4-inch of head space, wipe rims with a clean cloth, and seal. Tap jars firmly on the counter to dislodge bubbles. Set filled jars in a boiling water bath (with enough water to cover the tops by an inch), cover pot, and boil for 10 minutes. Carefully set jars on a heat resistant surface, and allow to cool undisturbed. Lids should invert and seal as jars cool. If one of the lids doesn't seal, set jam in the refrigerator and consume right away.

*Calcium water is part of the Pamona's jelling system. It comes with a pack of Pamona's Pectin.