What sort of sand do sand sculptures use?

Question

http://sandstormevents.com.au/index.php?option=com_content&task=view&id=19&Itemid=56

In the second paragraph 3rd line down they descibe it as 'heavy sand'

http://www.turtlenursery.com.au/index.htm

i then went to "turtle" (arn't i cool) and the list of sands doesn't mention this "heavy sand"

In the first link it also mentions :Sculptors use a special kind of sand that is also used on building sites and was most likely used in the foundations of your home.

Thanks for your help!!

Answer 1

  Some sand has sharp particles and a bit of clay and salt in it - naturally at the beach - while other sand has rounded particles and does a very bad job of packing.  Beach sculptures are done with this sand kept damp.

  The sand used for building sites is commonly called "bedding sand" and when it is pounded it forms a surface that is very firm.  

  If sand is mixed with sodium silicate (water glass), it is sticky and after a while being exposed to the CO2 in the air, forms a hard carbonate that binds the sand into a strong mass.  It is used to make sand cores for casting metal.