I cut up a sheet into 6 ½ to 7 inch squares, size of sheet depends on what size cup you use. I use a red solo cup. Then put the sheet piece over the top of the plastic cup and secure it with the rubber band – it will look like a little drum. Choose one of the colors of sharpie pen and make dots in the center of the sheet piece. Choose another color and make more dots. Repeat. The circle of color should be about the size of a quarter. Now slowly squeeze about 20 drops of rubbing alcohol into the center of the circle of dots. Wait a minute and then you can add more drops. I usually have to put around 30 drops to get the colors to the edge of the cup. Drip the rubbing alcohol really slowly. What do you see happening to the ink? The rubbing alcohol will dry pretty quick.
How does it work?
This experiment shows you solubility, color mixing, and the movement of molecules. The Sharpie markers contain permanent ink, which will not wash away with water. Permanent ink is hydrophobic, meaning it is not soluble in water. However, the molecules of ink are soluble in another solvent called rubbing alcohol. This solvent carries the different colors of ink with it as it spreads in a circular pattern from the center of the shirt.
Warning: Rubbing alcohol is very flammable and must be kept away from any open flames or heat. This experiment must be conducted in a well-ventilated area, preferably outdoors or in a room with open windows.