Preparation

Prepare the fruit

• Wash the fruit in warm, soapy water, rinse, and dry well. Using a very sharp knife, cut both ends off the fruit. Cut each fruit lengthwise into 6 to 8 wedges. Lay each wedge on its side and cut the white center strip of membrane away from the fruit. Remove and reserve any seeds. Cut each wedge crosswise into slices that are no more than 1/4 inch thick.
• Put the sliced fruit in a bowl or container that will fit in your refrigerator and cover with the filtered water. Tie the reserved seeds into a square of cheesecloth and add it to the bowl. Cover and refrigerate for at least 8 and up to 24 hours.

Make the marmalade

• Put 2 small plates in the freezer (they are for testing doneness later).
• Transfer the fruit, seed bundle, and all of the liquid to a wide 8-quart pot. Add the sugar and stir to combine. Bring to a boil over medium heat, stirring often, about 25 minutes. Clip a candy thermometer to the side of the pot and boil vigorously, stirring often, until the mixture is between 217°F and 220°F, about 45 minutes more. To test for doneness, spread a small spoonful of the marmalade in the center of one of the frozen plates. Let it sit for a minute and then push your finger through the marmalade; you’re looking for it to wrinkle and not flood back in to fill the gap. If it’s too loose, cook for 5 to 10 minutes more and test again.
• Remove the cheesecloth bundle and squeeze it well with a pair of tongs over the pot. Stir the marmalade to distribute the slivers of rind evenly throughout.

Process the marmalade

• Fit a large pot with a low rack on which the jars will sit. Fill the pot with enough tap water to cover the jars by about 1 inch, add the vinegar, and bring to a boil.
• Ladle the warm marmalade into clean, warm 8-oz. (half-pint) jars, leaving 1/2 inch of space at the top. Wipe the rims with a damp paper towel and cover with the lids, tightening until the rings just meet resistance. Using a sturdy pair of tongs or a jar lifter, lower the jars into the pot and boil for 10 minutes. Remove the jars from the pot and place them on a folded kitchen towel. Let sit undisturbed for at least 1 hour to allow the jars to seal (you will hear popping noises, the sign of a good seal). Check the seals by gently pushing down on the lids; they should be firm and slightly concave. A well-sealed jar has no wiggle in the lid.

Make Ahead Tips

Once processed, sealed jars are shelf-stable for up to 1 year. Unsealed jars should be refrigerated and used within 1 month.

Cardamom-Orange Marmalade:Crush 1 Tbs. green cardamom pods and add them to the cheesecloth bundle.

Honey-Ginger Orange Marmalade:Peel and coarsely chop a 2-inch length of fresh ginger, and add it to the cheesecloth bundle. Reduce the sugar to 3 cups, and add 1-1/2 cups honey.

Holiday-Spice Marmalade:Add 2 crushed cinnamon sticks and 1 tsp. whole cloves to the cheesecloth bundle.

Three-Citrus Marmalade:Replace 1 lb. of oranges with 1 lb. of grapefruit.