Sprinkle the gelatin over cold water in a small bowl and let it rest for 2 minutes to soften.Place the bowl into a saucepan with barely simmering water until the gelatin dissolves.Add glucose mix well.Stir in the glycerin and off the stove.
Sift 6 cups of icing sugar into a large bowl. Make a well in the center and pour the glycerin mixture into the well in the icing sugar and stir with a wooden spoon until combined. The mixture will be very sticky.
Sift some of the remaining sugar onto a smooth work surface and transfer the sticky fondant and start kneading adding a little more sugar if necessary, to form a smooth.Rub the butter on your thumbs and knead it into the fondant.
Wrap the fondant in plastic wrap and place in a plastic bag. Allow the fondant to rest for some hours before using.