Place the chopped rhubarb and water in a saucepan. Bring the mixture to a hard boil, then reduce the heat to a simmer.

Simmer the rhubarb and water for about 20 minutes, until the rhubarb has completely broken down.

Pour the rhubarb mixture into a jelly bag (or cheesecloth-lined fine mesh strainer). Let the rhubarb juice drain for at least 2 hours, or until you've collected 4 cups of juice.

Pour the rhubarb juice back into a saucepan and bring it to a boil.

For a full sugar recipe, add the pectin and sugar into the boiling juice. If using Pomona's pectin, add the calcium water to the rhubarb juice, then mix the powdered pectin with the sugar separately, and add the sugar to the boiling juice.

Regardless of the pectin choice, return the juice/sugar/pectin mixture to a boil and boil hard for 1-2 minutes, stirring constantly.

Turn off the heat and pour the finished rhubarb jelly into prepared jars, leaving 1/4 inch headspace.

Store the preserve in the refrigerator (or freezer) for immediate use, or process in a water bath canner for 10 minutes for a shelf-stable rhubarb jelly.