If using fresh rhubarb, wash, trim, and weigh, then cut into small pieces and place in a large saucepan with the water and the bruised ginger, tied in muslin.
Bring to the boil and simmer gently, stirring occasionally to prevent sticking, until the rhubarb is soft. Make sure all of the added water is evaporated off.Add the Sure-Set, stirring until it is dissolved.
Bring back to the boil and boil vigorously for 4 minutes. (See 'Adding Sure-Set' for details on boiling and timing).
Remove the muslin bag.
Pot and cover in the usual way; label and date. (See 'Potting and covering' for details).
