- Rinse the calamondins and cut them in half crosswise. Working over a bowl or large measuring cup to collect the juice, use your fingers or a paring knife to dig out and dispose of the seeds. You’ll need 4 cups of juice, flesh, and rinds. Put the fruit (including the rinds) in a food processor and, using the slicing blade, pulse a few times; the mixture should be somewhat chunky, not pureed. You can also do this with a knife if you don’t have a food processor, but be sure to catch the juices that come out as you slice.
- Put the oranges in a heavy non-corrosive saucepan and add the water. Bring to a rolling boil. Continue to boil for 15 minutes, then remove the pot from the heat and let the mixture stand overnight (refrigeration isn’t necessary).
- The next day, return the orange/water mixture to the stove and bring to a boil. Add the sugar to the pot very slowly, a little at a time (it can take as long as 10 minutes to add it all). Keep stirring as you add the sugar until it’s completely dissolved. Attach a candy thermometer to the pot and cook until the mixture reaches 220 degrees.
- Remove the pot from the heat, ladle the marmalade into jars, and seal. Because of the high acid level of the marmalade, you don’t need to process the jars in a hot-water bath.