Europe's biggest sandcastle, depicting the Bruges skyline, has been built at Zeebrugge in Belgium, but did the sculptors do it all with buckets and spades? William Hartston has his doubts
There is a corner of a foreign beach that is forever England. And you can be fairly sure it has a sandcastle on it. Look around you when you're on holiday abroad and you will discover that making sandcastles is a curiously British thing to do. The Germans will sunbathe, swim and towel-drape, but they don't make sandcastles. Which makes it all the more surprising to hear that Europe's biggest sandcastle, pictured above, has been constructed by more than 50 sand sculptors from Denmark, Ireland, the United States, Belgium and the Netherlands. It is 13 metres high and 51 metres wide, used 10,000 tonnes of sand and took them 10 days to complete.

"By the time we have finished," said the Dutch project leader, Eppo Vogel, half-way through the project, "it will have taken 10 man years to sculpt it, and in a month it will have worn away." Others described the whole project enthusiastically as a "monument to disposable art".

But are all those intricate carvings really made of unadulterated sand? After a little chat with our architecture correspondent, Nonie Niesewand, I have my suspicions that the sandmen in Zeebrugge may not have played totally fair. Ms Niesewand remembers taking a party of British architects in the late Eighties to make sandcastles on Cumber sands for a feature in Vogue magazine. It was the depth of the recession and the poor chaps didn't have anything better to do, it seems. Lord Snowdon tagged along too, to take some seaside snaps.

Each of the architects was allowed one assistant, one extra prop of his own choosing, and a bucket and spade, and their choices and subsequent methods of castle construction throw a good deal of light on the techniques that may have been used in Belgium.

John Poulson had the right idea from the start. He asked for some quick- drying cement to add to the sand. David Chipperfield preferred builder's glue so that he could make his castle as a cardboard cut-out, then glue sand on it at the end to create that genuine sandcastle effect. "Pure facadism," says Ms Niesewand.

Ron Arad found a trick the Belgians clearly missed - he used one of those compressors road-builders use to drive jackhammers, then built a splendid volcanic construction that used compressed air to spew out sand. The only trouble was that local council regulations forced them to use it near the road, where the sand was rather coarse, leaving the whole extravaganza liable to shower bystanders with pebbles.

Combining their methods, and those of the other architects who participated in the project, we can make the following recommendations for anyone serious about their sandcastles.

1. Have a survey done. It is vital to choose the right type of sand - alluvial sand with high clay content makes the best castles. You must also select the correct place on the beach, to ensure that the sand is wet enough, yet not so close to the sea that it will be washed away too quickly. Consult the local coastguard and tide tables to assess the likely affect of waves on your construction. If in doubt, employ a surveyor. One architect on the project spent so long surveying the beach that he did not leave himself with enough time to build the castle.

2. Practise beforehand. Any time you can spare at a local builder's merchants playing with their sand will be well spent. It is essential to gain familiarity with your materials before embarking on a task of this nature.

3. Choose a photographer with care. The sort of fine sand that makes the best castles can be very damaging to a good camera. Ensure that your photographer has had sufficient experience working in these conditions. On balance, several of the architects thought that a Gulf War cameraman might have been easier to deal with than Lord Snowdon.

4. Consult the scientific literature. The relevant paper was published earlier this year in Nature. Until recently, scientists had been unable to explain why sandcastles stay up after the sun has dried them. After all, as every child knows, you cannot make a sandcastle with dry sand, yet if you make it with wet sand it does not collapse after drying out. The answer, as discovered by physicists at the University of Notre Dame, Indiana, lies in what they call the "wet sandcastle effect", a phenomenon that affects granular material coated with liquid. Experiments with minute polystyrene balls coated in thin films of oil showed that the liquid forms tiny bridges between the grains, holding them together like mortar gripping bricks. A minute amount of oil added to the polystyrene greatly increased the "angle of repose" - the steepest stable slope the grains could form. "Our results indicate that interstitial liquids can alter many aspects of pattern formation, self-organisation and segregation in granular material," the paper concludes. And without it, they might well have continued, sandcastles would all fall down.

Finally, two practical recommendations for anyone who feels they lack the necessary artistic skills. First, and the most practical application of the research in Nature, is the sludge castle. You build this simply by dribbling very wet sand in a steady trickle from your hand. You will find it makes wonderfully Disneyesque gothic turrets quite effortlessly. Second, forget sandcastles, try sand sculpture. Sand is the easiest stuff to sculpt. Any errors, and you can fill in the holes immediately. It's child's play to build your own crocodile crawling out of the sand. And from personal experience I can tell you it scares the hell out of the Germans.