In a medium saucepan, combine the water and sugar and bring to a boil. Add the kumquat slices and cook over moderate heat, turning them occasionally, until the liquid is reduced to a thin syrup and the slices are translucent, about 20 minutes

. Reduce the heat to moderately low and simmer until the syrup is thick and the slices are tender but still intact, turning occasionally, about 10 minutes. Transfer the slices to a rack to cool.