Sand grains tend to stick to each other and to our skin when water is present, via tiny liquid bridges held together by surface tension. However, official volleyball sand is designed to have excellent drainage, which minimises the water content.
The International Volleyball Federation (FIVB) has strict specifications for sand, which must be sieved so that it’s neither “too coarse” nor “too fine to cause dust and stick to the skin”. The grains also have to be naturally weathered to give rounded edges that aid flow and drainage.
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Dr Emma Davies is a science writer and editor with a PhD in food chemistry from the University of Leeds. She writes about all aspects of chemistry, from food and the environment to toxicology and regulatory science.