Cut the kumquats lengthwise. Remove and keep the seeds aside. Bind the seeds into a cheesecloth.
Peel the lemon and orange, remove the white inner part from the peel and slice into julienne (the zest). Cut all segments out of the membranes.
Weigh the kumquat, orange and lemon segments together and add 50% to 60 % of the weight in caster sugar.
Cook the marmalade:
Place all fruits, sugar, water and the seed bag into a cooking pot.
Bring the mixture to the boil, leave it uncovered and let it cook for 20-30 minutes or until the zest slices are soft.
Stir occasionally and use a skimmer to remove impurities from the surface.
Check if the marmalade is cooked properly. Transfer the hot kumquat marmalade into a sterilized glass jar. Close firmly and place the jar upside down to cool.