How does one make a sand castle that is strong enough for those extra crenellations? By using the correct mix of sand and water. Researchers at the Amsterdam University found that a mixture of sand and one percent water is the ideal for making sand castles. Daniel Bonn, a physicist, believes with this mixture one can build castle up to twenty feet high.
“Here we investigated the stability of wet sand columns to account for the maximum height of sandcastles. We find that the columns become unstable to elastic buckling under their own weight. This allows to account for the maximum height of the sand column; it is found to increase as the 2/3 power of the base radius of the column.”
In other words, it’s about one teaspoon of water per pound of sand.
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