How to grow a rainbow at home
A beautiful rainbow which you can make at home in 5 minutes
Is it possible to grow a rainbow at home without leprechauns? Learn how with this video!
- paper towel;
- water-based markers;
- Petri dish;
- paper clip;
Use some markers to draw the beginnings of a rainbow on a paper towel. Use a paper clip and some thread to suspend the paper towel above a Petri dish. With the addition of water, your rainbow begins to inch towards the sky!
A material is considered “wettable” if it interacts with water more strongly than water molecules interact amongst themselves. Water strives to maximize contact area with a “wettable” material, and spreads out over the surface. In our experiment, the water thus “wets” the paper towel, but gravity interferes with its ability to rise through it. However, once in the narrow capillaries of the wetted material, the water’s surface adopts a concave shape, forming a meniscus. Meanwhile, the water pressure under this meniscus becomes lower than atmospheric pressure, and the water begins to rise. A paper towel consists of plant fibers that have numerous capillaries in their structure that the water can rise through. The thinner the capillary, the higher the water rises, trying to balance the pressure difference. The water thus moves upward through the material, lifting the dye molecules with it.