Sandcastle building is no child's play

The recipe for the perfect sandcastle? A delicate balance of 99 percent sand and one percent water, say physicists who have given new meaning to mixing work and play. For their contribution to science, researchers in Amsterdam and Paris spent hours building beach sand columns in their laboratories to come up with a complicated mathematical formula for a stable and long-lasting sandcastle. Not too much water, they concluded -- just enough to form small "bridges" between grains of sand, making them stick together. "If this optimum concentration is used, sandcastles reaching five meters in height can be built," said a statement on the report that elevates a popular childhood pastime into the pages of the journal Nature Scientific Reports. The formula also sets out the desired height-to-base-diameter ratio and sand compacting force. The findings are of interest for civil engineering and soil mechanics, fields which deal with structural stability, wrote the scientists. "In addition, it explains the maximum height of, and provides us with a recipe to construct the perfect sandcastle."