Water Dome Shaped Like an Umbrella

Let's take a look!

What type of experiment is this?

Experimental procedure and explanation:

• I cut the lid from a candy package purchased at a convenience store into a piece about 2 cm in diameter and attached it to a plastic bottle cap, creating a concave surface. When water is poured onto it, the water dome opens up like an umbrella.
• Next, by reducing the flow rate, a small dome forms.
• When you touch this dome with a chopstick, the umbrella expands. Disrupting the water film with the chopstick weakens the effect of surface tension, causing the dome to expand.
• The same expansion occurs when spraying with dishwashing detergent.
• 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?, Dishwashing Detergent Makes the Dome Larger
[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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