Permanent Sand Castle 2 C. sawdust 1 C. wallpaper paste powder 1 C. water Sand castle molds, cans or paper cups Forks, knives and spoons Mix sawdust and wallpaper paste powder with your hands in a large bowl. Add water and stir until it mixed well. Pack the mixture into a mold, then carefully take it out. When you're done, let it dry in a sunny place for a few days. You can decorate the sand castle with sea shells or paper flags.