Special equipment Edit
- Combine rhubarb, sugar and orange zest in mixing bowl.
- Cover with plastic wrap, and refrigerate for 12 hours.
- Strain liquid from rhubarb mixture into a large heavy saucepan, pressing on solids to release all juice.
- Set rhubarb aside.
- Bring liquid to a boil, and cook over medium heat until syrupy and reduced by half, for 15 to 20 minutes, watching closely toward end to prevent scorching.
- Add reserved rhubarb and crystallized ginger, and cook, stirring, until rhubarb is soft and mixture has thickened, for about 5 minutes.
- Pour into hot, sterilized half-pint jars, leaving ¼-inch headspace.
- Tighten lids, and process in a boiling-water bath for 10 minutes.
- Remove from heat, cool and store.