Sift powdered sugar and put into large bowl; make a well in center and set aside. Soak gelatin in water in a small sauce pan. When gelatin is softened, dissolve over low heat until grains disappear. Add glucose and glycerine. Let mixture come nearly to boiling point. Pour mixture into well in powdered sugar. Mix with a wooden spoon, pulling sugar into the liquid from the center. Continue mixing until stiff. Turn onto board and knead. Mixture should be firm. Amount of sugar needed may vary. Form into a ball and grease lightly with shortening. Put into heavy plastic bag and place bag in an air-tight container.