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Author Topic: Why can I build castles with WET sand?  (Read 1677 times)

Offline saligari

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Why can I build castles with WET sand?
« on: 23/12/2014 22:22:13 »
Hi, I am Chris and I was wondering why it's possible to build castles with wet sand at the beach and not with dry sand. This happens with soil and mud as well. One could shape things with mud but not with soil. So what does water do that makes things mold-able ?


 

Offline evan_au

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Re: Why can I build castles with WET sand?
« Reply #1 on: 24/12/2014 09:05:56 »
Perhaps the surface tension of the water holds the wet sand grains together?

Sand grains tend to slip past each other when the pile exceeds the angle of repose. This angle can vary from about 15 to 45. Too much or too little water will cause your masterpiece to collapse.

Sand sculptors are also careful about the kind of sand that they use...

Also see: https://van.physics.illinois.edu/qa/listing.php?id=680
 

Offline evan_au

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Re: Why can I build castles with WET sand?
« Reply #2 on: 31/12/2014 11:32:11 »
I saw an interview with a team doing sand sculpture, including popular movie characters. There were parts of the sculpture that were vertical (ie greater than the angle of repose for wet sand).

They commented that they spray the sand with a mixture of glue and water to hold it in position (ie they "cheated").

But the sand sculpture definitely looked impressive!
 

Offline nicephotog

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Re: Why can I build castles with WET sand?
« Reply #3 on: 11/01/2015 00:12:27 »
A simple quick explanation is to look at a drop of water under a leaf or object such as wood eves rafters e.t.c. after rain and you will see the droplet hangs underneath and sticks to the surface.
Water is H2O and is polar covalently bonded - meaning - the electron bonds that orbits the oxygen and hydrogen atoms is in a state of "both covalent bonding and ionic" bonding.
In plant osmosis ionic attraction with water and salts allows the ionic bonding force to attract water from one side of a membrane to the other.
This ionic attraction occurs when molecules of water are together causing a powerful enough attraction for small "total weights of water" (example size of a drop of water) to hold together against gravity or any other surface.
The other half of wet sand holding together is its piling effect of being a heap of microscopic rubble.
The two processes together makes it more efficient at holding together.
 

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Re: Why can I build castles with WET sand?
« Reply #3 on: 11/01/2015 00:12:27 »

 

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