01 -
Wash the limes thoroughly. Cut off the blossom and stem ends, discarding them. Slice the limes thinly using a sharp knife or mandoline, then quarter each slice. Alternatively, quarter the limes and pulse in a food processor until evenly chopped but not mushy. Combine the limes with 8 cups of water in a large container, stir well, cover, and let sit overnight.
02 -
In a large saucepan or jam pot, bring the lime mixture to a boil and continue boiling uncovered for 40 minutes until the peels soften. Gradually add 6 cups of granulated sugar to the boiling mixture, stirring constantly to dissolve completely. Taste and add up to 1 additional cup of sugar if desired. Remove from heat, cover, and let it sit for 6 hours or overnight.
03 -
Prepare jars or containers for storage and set up a hot water bath if canning. Bring the lime mixture back to a boil over high heat, stirring continuously to prevent scorching. Add a little water if the mixture is too firm. Cook the marmalade until it starts to firm up but retains some syrup consistency, using the cold plate test or confirming the temperature is between 216 to 218°F. Taste and add freshly squeezed lemon juice as desired. Add green food coloring, if using. Let the mixture rest for 10 minutes while preparing containers. Stir the marmalade thoroughly to ensure even distribution and ladle into jars or containers. Leave 1/4 inch headspace for canning or 1 inch for freezing. Process jars in a hot water bath for 10 minutes (15 minutes above 6,000 feet). Cool jars for 24 hours, ensuring proper seals before storing. Refrigerate opened jars or unsealed jars.