01 -
Trim off the tough stem ends. Remove obvious seeds, then slice the limes very thinly with a sharp knife or mandoline. Cut the slices into quarters if you want smaller peel pieces.
02 -
Combine the sliced limes and water in a large nonreactive bowl or pot. Cover and let stand at room temperature for 8-12 hours.
03 -
Bring the lime mixture to a boil in a large jam pot. Boil uncovered for about 40 minutes, stirring now and then, until the peel is tender and bends easily.
04 -
Stir in the sugar gradually until fully dissolved. Remove from the heat, cover, and let stand for 6-12 hours to help the natural pectin develop.
05 -
Return the mixture to a boil over high heat. Stir often and cook until it reaches 216-218 F or passes the cold plate wrinkle test. Remove the pot from the heat while testing so it does not overcook.
06 -
Taste carefully once the bubbling slows. Stir in lemon juice and a pinch of salt if needed. Let the marmalade stand for 10 minutes, then stir to distribute the peel.
07 -
Ladle into clean jars. For refrigerator storage, cool and chill. For freezer storage, leave 1 inch headspace. For water-bath canning, leave 1/4 inch headspace and process according to current safe canning guidance for your altitude.