Wash the kumquats and oranges with clean, cool water, gently rubbing with your hands or a vegetable scrubber.

Slice the kumquats crosswise into thin slices. Do not remove the peeling, but seeds may be discarded. Slice enough kumquats to equal 2 cups.

Cut the oranges in half and scoop out the orange pulp, removing any seeds. Chop the orange pulp to obtain 1½ cups.

Remove the white pith layer from the inside of the orange rinds, and retain only the outer layer of peeling from the orange. Cut the peeling into thin slices or small pieces, equaling 1½ cups.

Mix the kumquats, orange pulp, orange peels, lemon juice, and water in a large saucepan.

Bring the fruit mixture to a boil over medium-high heat, then reduce the heat to medium and gently boil the mixture for 5 minutes.

Place a cover on the saucepan or transfer the mixture to a container with a lid and refrigerate for 12 to 18 hours.

Return the fruit mixture in a large saucepan to the stove and cook over medium-high heat. Continue to cook, stirring occasionally, until the peelings are tender.

Measure the fruit mixture, including the juices, then add an equal amount of sugar to the mixture and stir until the sugar dissolves.

Prepare jars and a hot water bath.

Return the fruit and sugar mixture to a rolling boil, stirring continuously, and continue to boil hard until it reaches the gel stage or when the mixture reaches 220° Fahrenheit.

Remove the marmalade from the stove and skim off any foam with a metal spoon if desired.

Immediately pour or ladle the hot marmalade into prepared hot jars, leaving ¼" headspace at the top of the jars.

Wipe the rims of the jars with a clean cloth, and apply the 2-part canning lids.

Preserve the marmalade using a hot water bath canning method for 10 minutes, 15 minutes at altitudes above 3000 feet, or 20 minutes above 6000 feet.

After processing, turn off the heat and leave jars in the canner, uncovered, for 5 minutes. Remove the jars from the canner and let them cool and seal for 12-24 hours or longer. It may take up to a week for the marmalade to set firmly.

Sealed marmalade will retain peak quality for up to 12 months stored in a cool, dry place or pantry. Refrigerate the marmalade once opened.