Dishwashing detergent Makes the Dome Larger

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What type of experiment is this?

Experimental procedure and explanation:

• We learned that the water dome grows larger when touched because the water film is disrupted, weakening the effect of surface tension. If this is true, the same phenomenon should occur when surface tension is weakened by another method.
• To test this, I sprayed the water dome with diluted dishwashing detergent.
• When sprayed upstream of the water flow, the dome grew larger— demonstrating the same effect as touching it with a finger.
• Dishwashing detergents contain surfactants, which reduce surface tension, causing the dome to expand in the same way.
• Finally, I sprayed the dome with plain water, but no change occurred. Since water does not contain any components that weaken surface tension, the dome did not grow larger. This confirms that touching the dome with a finger or spraying it with dishwashing detergent weakens the surface tension effect, causing the dome to expand.
• This video was produced with the support of the JSPS Grant-in-Aid for Scientific Research (18K03956).

[Attention]	Water is used throughout these experiments, but it’s important to remember that water is a valuable resource. To minimize waste, consider reusing the water after each experiment—for bathing, cleaning, watering plants, and other practical purposes.
[Keywords]	Surface tension, inertia
[Related items]	What Causes the Water Dome to Grow?
[References]	Ryozo Ishiwata and Mitsumasa Nemoto, “The Wonder of Flow,” Kodansha Bluebacks, pp. 62–67. Ryozo Ishiwata, “Illustrated Fluid Dynamics Trivia,” Natsume Publishing, pp. 48–49.

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