Wash the grapes and pluck them off their stems. Put them in a pot with a tight-fitting lid and add two cups of water. Set over high heat and bring to a boil. Reduce the heat to medium-low and simmer for 20 minutes.

Once the grapes are soft, remove them from the heat. Let them cool.

Fit a food mill with its finest screen and set it over a bowl. Pour the cooked grapes into the food mill and work them through.

Measure out eight cups of the grape juice and pulp pour it into a preserving pan. Add 1 1/2 cups of sugar and the calcium water.

Prepare a boiling water bath canner and five half pint jars.

Bring to a boil and cook for 20-25 minutes, until the liquid has reduced by about 1/4. Whisk the pectin into the reserved sugar and add it to the boiling pot in stages, stirring between each addition so that the pectin doesn't clump.

The jelly is done when it sheets thickly off the back of a spatula and forms thick layers on the walls of the pot.

Remove the pot from the heat and funnel the jelly into the prepared jars. Wipe the rims, apply the lids and rings, and process in a boiling water bath canner for 10 minutes.

When the time is up, remove the jars and set them on a folded kitchen towel to cool. When the jars have cooled enough that you can comfortable handle them, check the seals. Sealed jars can be stored at room temperature for up to a year. Any unsealed jars should be refrigerated and used promptly.