Floating a 10-Yen Coin

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Watch the video on YouTube.

What type of experiment is this?

Experimental procedure and explanation:

• Float a piece of tissue paper on top of water, and then place a 10-yen coin atop the tissue paper.
• The tissue paper continues to float without sinking.
• The tissue paper was sprayed in advance with a waterproof spray. The waterproof spray has a force that causes repellency between the spray and the water molecules, thus water is repelled. This property of repelling water in this manner is referred to as water repellency.
• The bottom surface of the tissue paper repelled water. Moreover, numerous air bubbles remained, thereby increasing buoyancy. As a result, the tissue paper could support the weight of the 10-yen coin.

[Attention]	Some waterproof sprays also contain harmful components; therefore, be certain to apply the spray outdoors or in a well-ventilated area.
[Keywords]	surface tension, water repellency
[Related items]	Blowing Away Tissue Paper
[Reference]	The Japan Society of Mechanical Engineers, “The Wonders of Flow (Nagare no Fushigi),” Kodansha Blue Backs, pp. 68–71. Ryozo Ishiwata, “Illustrated Fluid Dynamics Trivia (Zukai Zatsugaku Ryutai Rikigaku),” Natsume Publishing, pp. 48–49.