Unless you’re a fan of reading or water sports, building sand castles is still a seaside vacation “must”. But how do you make your castle look as majestic as it is sturdy? Luckily, there is a scientific formula that just might help you.
It all started in 2004, when a tour operator asked my team to investigate the matter. As a sedimentologist, that is to say a specialist in rock deposits left by water, wind and glaciers, I started by thinking about the type of beach that was best suited to building sand castles.
I conducted the investigation by comparing the sand of the ten most popular beaches in Britain (at the time). Although you can really build castles on any beach, Torquay topped my rankings with its stunning red sands, followed closely by Bridlington, while Bournemouth, Great Yarmouth and Tenby vied for the 3rd place. At the very bottom of the ranking was Rhyl Beach.
But once the beach has been selected, you still have to find the ideal location. This question is rather a function of individual preferences: some prefer to settle near the car park, to be able to clear off in the event of a shower, while others prefer the proximity of a café. Still others opt for an isolated spot, perhaps better protected from the wind by a natural promontory.
If you want to build a real fortress, it is better that your building stands upright. And for that, you need solid sand! The strength of sand depends on two factors: the properties of the grains that make it up and the water that allows them to bind together.
If the sand contains too much water, your castle will drip, if there is too little, it will crumble. You must therefore find the right proportions, so that your castle stands straight, and for a long time. It’s all a function of water’s surface tension, or “water meniscus,” the phenomenon that makes a glass of water on a damp, smooth surface seem hard to move.
Our experience has shown us that to build the perfect sandcastle, you need 1 bucket of water to 8 buckets of dry sand. Or if you prefer, here’s the magic formula: water = 0.125 x sand. But if you don’t have scientific equipment, don’t panic! All you have to do is find a spot in the strip of sand between the high tide line – easily spotted by a pile of seaweed and marine debris – and the low tide line. Keep in mind, however, that this area moves during the day, depending on the tides.
So that the atmosphere of the team remains harmonious, plan a wide selection of tools. The size and shape of the bucket are also important. Prefer simple, round buckets to those that take the form of a castle with crenellated towers. A round bucket will allow you to produce a lot of turns and details to achieve the monument of your dreams, by making your imagination work.
And as you build, keep a thought for the story, not just the imaginary story of the castle and its cohort of outdated fairy tales, but also the real story of the sand you’re handling. Each grain is indeed a fragment of rock that encapsulates a long history of vanished mountains, ancient rivers, dinosaur-infested swamps and seas, climates and events of the past: all elements that tell the story of our planet.
Finally, a word about the size of the castle. While you can get away with a modest castle with pretty towers, ramparts and moats, the castles that make a difference on the beach and are the most successful are also the most imposing. Think big! Pebbles, shells, driftwood and feathers can embellish your work.
Besides, let’s be honest: a sandcastle is meant to be admired. And while there’s a bit of science behind the perfect castle, most importantly, have fun building it.
* Matthew Robert Bennett is Professor of Environmental Science and Geography at Bournemouth University (UK).
