0:00:28 > 0:00:32Look on any sandy beach on a sunny day, and you can guarantee
0:00:32 > 0:00:36that there will be dozens of aspiring architects at work.
0:00:36 > 0:00:38As with any other property
0:00:38 > 0:00:40the key to its success is its location.
0:00:40 > 0:00:45Many resorts would have you believe that their sand is the best for building sand castles.
0:00:45 > 0:00:50So along our journey we've chosen three great holiday spots to put that to the test.
0:00:50 > 0:00:56Here in Weymouth, then Lyme Regis and finally Torquay.
0:00:56 > 0:01:00With the help of Professor Matthew Bennett of Bournemouth University,
0:01:00 > 0:01:05we're going to put the sand from each resort through a series of experiments
0:01:05 > 0:01:09to reveal which beach has the best chance of making the ultimate sand castle.
0:01:09 > 0:01:14What's the most important thing to look for when you're looking for the perfect sand to make a sand castle?
0:01:14 > 0:01:19OK, I think it's probably water, because the water, the right mix of sand and water,
0:01:19 > 0:01:22is the thing that's gonna make it stand up or fall down.
0:01:22 > 0:01:24So kind of stick the sand together.
0:01:24 > 0:01:27Right, so it's this property of cohesion, is the posh word
0:01:27 > 0:01:31for that stickiness of the water, because it binds the grains together.
0:01:31 > 0:01:35Now by lots of experimentation we reckon that the best
0:01:35 > 0:01:41ratio of water to sand is eight parts sand to one part water,
0:01:41 > 0:01:44but if you're wanting to build sand castles on the beach
0:01:44 > 0:01:46you need to know where to look.
0:01:46 > 0:01:50- Do you think you can actually spot this consistency on the beach then? - Yeah.
0:01:50 > 0:01:54- So where shall we start? - Try and make a sand castle here and see what happens.
0:01:54 > 0:01:59This is feeling a lot more like your eight-to-one mix.
0:01:59 > 0:02:00OK.
0:02:04 > 0:02:08- That's fantastic.- The key thing is the smoothness of the sides.
0:02:08 > 0:02:11- It's lovely and smooth. - Just right there.
0:02:11 > 0:02:15Now we're off to Lyme Regis and Torquay in our quest to find
0:02:15 > 0:02:17the perfect sand castle sand.
0:02:18 > 0:02:24Lyme Regis Council put a lot of effort into researching different types of sand for their new beach.
0:02:24 > 0:02:27They believe they've found the perfect complement to their sea front,
0:02:27 > 0:02:30but is it any good for sand castles?
0:02:30 > 0:02:32We take a little bit of French sand...
0:02:32 > 0:02:35We'll examine the quality of the French sand grains
0:02:35 > 0:02:38to see how it compares to the Weymouth sand we tested earlier.
0:02:38 > 0:02:42The first thing that's obvious is that the Weymouth sand is much more homogenous.
0:02:42 > 0:02:46- That's right.- It's similar grains throughout, very fine.
0:02:46 > 0:02:50I'll just compare it now with the French sand here at Lyme Regis.
0:02:50 > 0:02:53It's got a range of sizes - quite angular.
0:02:53 > 0:02:57This helps the French sand bind together a little bit more.
0:02:57 > 0:02:59All the different shapes interlock.
0:02:59 > 0:03:02But what do the people whose opinion really counts
0:03:02 > 0:03:05think about the new-look Lyme Regis sand?
0:03:05 > 0:03:07It's quite grainy, it's quite sharp.
0:03:07 > 0:03:11- Any hot tips then for building sand castles?- Pour water over it.
0:03:11 > 0:03:15Add a bit to the base as well, makes it solid to stick the castles on.
0:03:15 > 0:03:19- Right, so you've got to have solid foundations.- Absolutely.
0:03:19 > 0:03:23Torquay recently boasted that it had the best sand castle sand in Britain.
0:03:23 > 0:03:28It's a claim we're going to put to the test in the final stage of our sand castle quest.
0:03:28 > 0:03:33After putting Torquay's sand through the same experiments as Lyme Regis and Weymouth,
0:03:33 > 0:03:36we have discovered that Torquay and Weymouth are
0:03:36 > 0:03:40neck and neck in terms of grain size and the angle of internal friction,
0:03:40 > 0:03:42but Lyme Regis is not far behind.
0:03:42 > 0:03:45Now for the ultimate battle of strength.
0:03:45 > 0:03:51We're using measured amounts of water to increase the weight on top of our sand castles.
0:03:51 > 0:03:52Which one will crumble first?
0:03:55 > 0:03:56SHE GASPS
0:03:56 > 0:03:58Oh, there's definitely a crack there.
0:03:58 > 0:04:01This is going to be the fourth kilo.
0:04:03 > 0:04:05- Yes!- Yes!
0:04:05 > 0:04:09- I told you.- Lyme Regis, look at that!
0:04:09 > 0:04:12'The French and Lyme Regis have been knocked out already.
0:04:12 > 0:04:16'With only my Torquay and Matthew's Weymouth sand castles left,
0:04:16 > 0:04:19'it's down to a straight shootout between the two of us.'
0:04:19 > 0:04:23Mmmm... Aaaaah! SHE LAUGHS
0:04:23 > 0:04:26Let's see how many more Torquay can take.
0:04:28 > 0:04:31- Wow!- Seven kilos!
0:04:35 > 0:04:38- Whay!- Yes!
0:04:38 > 0:04:41Eight kilos. Torquay is the out and out winner.
0:04:41 > 0:04:44- It took eight kilos to flatten it. - Eight kilos...
0:04:44 > 0:04:46What a mess!