01 -
Process chopped watermelon in a blender until fully puréed and smooth. Strain the purée through a fine mesh sieve lined with cheesecloth or a jelly strainer bag into a large bowl or jug.
02 -
Measure 950 milliliters (4 cups) of strained watermelon juice; reserve any excess juice for another use.
03 -
Transfer measured watermelon juice to a saucepan. Add lime juice and pectin. Whisk thoroughly over high heat and bring mixture to a boil.
04 -
Boil the juice-pectin-lime mixture for 1 minute while whisking constantly.
05 -
Gradually whisk in the sugar, stirring to dissolve. Bring mixture back to a full rolling boil and cook for 1 additional minute.
06 -
Carefully ladle hot jelly mixture into sterilized jars, leaving 6 millimeters (1/4 inch) headspace at the top of each jar.
07 -
Wipe jar rims and sides with a clean kitchen towel. Secure lids and rings until fingertip tight.
08 -
Allow jars to cool at room temperature. Jelly will thicken and set over 12–24 hours. Refrigerate and enjoy within 3 weeks if not canning.
09 -
For shelf storage, process sealed jars in a hot water canner for 10 minutes (15 minutes above 1,800 meters elevation). Transfer to a towel-lined surface, leaving 2.5 centimeters between jars. Once cooled, check seals. Refrigerate any unsealed jars; store sealed jars in a cool, dry place up to 18 months.