Simple Science -- Magic Sand

Magic sand is ordinary sand which has been coated with trimethylsilanol, a compound which makes the sand resistant to water. The result is a hydrophobic sand which can be used in all sorts of interesting ways. Magic sand was originally developed for use in the cleanup of oil spills, but it has come to be used as a children's toy and educational tool instead. Many stores which sell science-orientated kid's toys stock magic sand.

Because magic sand resists water, it performs very strangely when it is exposed to water. Individual grains of sand tend to stick together in the water, creating blocks of sand underwater which can be molded into various shapes. When scattered lightly across the surface of water, magic sand will stick together and form a thin layer of sand which eventually get too heavy to float, sinking slowly to the bottom. Magic sand also appears slightly silvery underwater, thanks to the bubble of air which forms around the granules of sand.

When lifted out of the water, magic sand is perfectly dry and free-flowing. People who grew up playing with magic sand may remember how mesmerizing the mysterious substance was, as the seemingly solid underwater shapes would dissolve instantly when pulled out of the water.

The idea behind this sand when it was initially developed was that it could be scattered across an oil spill to bond to the oil. As the sand bonded with the oil and to itself, it would grow extremely heavy, eventually sinking to the bottom of the ocean and taking the oil with it. However, magic sand proved expensive to manufacture, and doubts were raised about the environmental soundness of this cleanup method.As a result of its commercial failure, the manufacturer was left wondering what to do with its new invention. The solution was to dye the sand in eye-catching colors, label it “magic sand,” “Mars sand,” or “space sand,” and sell it as a toy. Magic sand was immensely popular in the 1980s, much to the chagrin of parents who had to clean up after their children, and it continues to be used in scientific demonstrations of the properties of hydrophobic materials.

You can make magic sand at home, should you feel so inclined. Magic sand can be made by baking sand to remove the moisture and then coating it with a water repellent such as 3M's Scotchgard, tossing the sand to ensure that it is evenly coated.