why do they stand?

Sand sculpture seems magical, as if the artists working it possess the ability to defy gravity. But I can assure you this is not the case. Dancing a fine line between what looks good and what will stay is the challenge of any sand sculpture. It is a constant lesson in applied physics, if it won’t hold, it just falls.

But why do they stay? How do they stand? Why don’t they just fall down?

compaction

Let’s start at the top; compaction, the single most important element of sand sculpture. Without compaction, you just have a pile of sand. Compacted sand acts like a solid medium very much like a soft sandstone. Naturally occurring sandstone is formed as layer upon layer of sand is laid down by water, the weight of the layers above presses out the air and water compacting it into a block. When sand is compacted for sand sculpture the same principal applies, only a tamper or strong vibration replaces the weight of the layers above and the time it would take for nature to take its course. Water in the sand acts as a lubricant , much like oil on ball bearings, allowing sand particles to slide past each other and fall into position with themselves. The tamping and vibration speeds up the settling of the particles and helps release any air bubbles trapped in the sand that would create voids. The result; nice solid block.

support

From the solid block of sand shapes are sculpted and how they relate to each other, both visually and physically are of major importance. Each sculpted element must support the weight of that which is above, and the overall sculpture must be able to support itself.

This is a delicate balancing act, at any moment the sculpture could just give way. Any imperfection in the pack, any variation in the sand, a course layer here, could cause catastrophic failure.

adhesion

Particles of sand that are compacted into a block also tend to stick together, very much like velcro. Some elements can be sculpted out into open space, with no support beneath, using the adhesive qualities of the packed sand.

But be careful, some sand is only adhesive when it’s wet. I’ve seen sculptures fail two days into an event because they got too dry in the wrong places.

types of sand

“Is it just regular sand?” is a loaded question, and one of the most frequently asked. It’s a little like asking “is it just regular food?” Sand is created in nature in a myraid of ways but all sand is the result of rocks breaking down into smaller components. It’s what happens to sand after it is created that makes a difference.

Desert and ocean beach sand share one common fault, their particles are round. Sand that has been tossed by the waves or wind has had all the sharp edges removed, this reduces its ability to cling once packed. If you pick up a handful of beach or desert sand, moisten it and pack it into a ball, that ball will not stay packed. It will squish and deform and never hold its shape as you would like. There are a few exceptions of course, Gulf Coast sand has experienced less wave action and tends to be sharper and finer than true ocean sand.

Glacial sand on the other hand can be found underground in huge deposits left behind by retreating glaciers. This sand has experienced little to no weathering so it retains all its sharp jagged edges, when it contains a great deal of silts and fines glacial sand is some of the strongest, best packing and best carving sand known to humans.

Regardless of the quality of sand the reason a sand sculpture stays up is the result of the sand sculptor’s knowledge, experience and skill. There are no cheats or coverups, a true professional will know how to make any pile of sand look as good as it possibly can. Any professional will read the sand and formulate a piece within those obvious limitations.