In large bowl, place 4 cups confectioners' sugar; make a well. Pour the lukewarm gelatin mixture into the well and stir with a wooden spoon, mixing in sugar and adding more, a little at a time, until stickiness disappears. Knead in remaining sugar. Knead until the fondant is smooth, pliable and does not stick to your hands. If fondant is too soft, add more sugar; if too stiff, add water (a drop at a time). Use fondant immediately or store in airtight container in a cool, dry place.