Make a Milk Rainbow

Introduction

Have you ever seen a rainbow after a rainfall, or drawn a rainbow for fun? They can be fun to make using colorful markers or other craft supplies. But did you know you can actually make a simple rainbow using milk, liquid detergent (i.e., soap), and food coloring? How the rainbow is created by this mixture might surprise you! In this science activity, you will make your own milk rainbow and explore how detergent and surface tension are involved in its creation.

Credits

Materials

• Milk; 1%, 2% or whole. Avoid using non-fat milk.
• Red, yellow, green, and blue food coloring if you want to make a rainbow. Or substitute any colors you want.
• Liquid dish soap or liquid laundry detergent
• A plate or some other type of shallow dish, such as an aluminum pie tin. Make sure the bottom is flat and not wrinkled.
• Cotton swabs
• Paper towels are useful for cleaning up afterwards