Research has shown that water holds sand together by forming “liquid bridges” between the contact points of the grains. But too much or too little water will make the castle crumble.
So exactly how much water do you need to make a perfect sandcastle? Traditional estimates put the ratio at one pail of water for every eight pails of sand. But new research revises the amount of liquid down to just 1 percent.
That optimal mixture will allow your castle to reach a maximum height that equals roughly the radius of the base to the power of two thirds, the researchers say. That equation means it is possible to build tall, skinny columns of sand that won’t fall apart.