This demo should need no preparation unless the liquids should need changing. To change the liquids it may be necessary to empty the unit with a syringe and long needle. Rinse several times with ethyl alcohol and dry with a small air hose. Use water and food coloring for the bottom layer and castor oil for the top layer. Make sure all air bubbles are removed. Place on a level surface. If the unit has not been used in a long time it may be a good idea to flip it over several times to rewet the inner walls with oil before demonstrating. As the Plexiglas allows water to pass over time, it will be necessary to take the air out and refill with a small amount of water about every year.