As any sand sculptor worth his or her plastic shovel might guess, the strongest piles turned out to be the ones made from relatively damp sand. The reason: Water forms so-called liquid bridges in the narrow channels between sand granules. The high surface tension of these tiny bridges makes individual grains adhere into durable clumps. In other words, Kudrolli explains,"The sand grains come out sticky. They form a heap that's more stable.â€ The effect has its limits, though. If too much water is added, the sand particles are"drownedâ€ and no liquid bridges form. So what's the ideal recipe?"About 8 parts sand to 1 part water," Kudrolli says."Although our data indicate that anything from 6:1 to 20:1 sand-to-water would work."