Half a croissant, on a plate, with a sign in front of it saying '50c'
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Sortable Sand

Re-usable 'toy' for making sand pictures
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Tiny plastic beads of various colors which can be sorted after use. It seems that a sieve / separator would get clogged up given that everything has to be small. Thus, separation would be done in steps: low-density plastic that floats v. high-density that doesn't. A tiny iron core for half of the colors (assume they still float). I'm a little foggy on other binary filters. Maybe 2 sizes with enough difference not to clog a sieve, can static electricity be used (before the floating test)? Play set comes with all necessary sorting equipment, but not a mass spectrometer. Teaches some science, I guess.
obscuresttourist, Aug 21 2008

The Brazil Nut Effect http://findarticles..._20_160/ai_80747803
The "Brazil Nut Effect" is a hot topic in the study of the physics involved in mixing different sized particles. It originates from the way in which shaking a box of muesli will cause the Brazil nuts to rise to the top. The explanations are very interesting. It looks like particle size is much more important than weight. [hippo, Aug 21 2008]

The Brazil Nut Effect http://www.seed.slb...b/brazilnut/res.htm
Simple experiments, with pictures [hippo, Aug 21 2008]

Review of cell-sorting technology http://www.cytonome...ll_Sorting_Methods/
60's method of separating small stuff [csea, Aug 21 2008]

Hele-Shaw Cell http://web.ncf.ca/j...valanche/index.html
Avalanche Segregation and Stratification [baconbrain, Aug 21 2008]

[link]






       Different grades/weights of sand could be sorted by use of the 'Brazil Nut Effect' (links)
hippo, Aug 21 2008
  

       yes I like this. fun for making art, but also you can devise and present puzzles requiring the use of the sorting equipment...
conskeptical, Aug 21 2008
  

       oh yes, this doesn't fit all that well in the fasion/hat/flight category...
conskeptical, Aug 21 2008
  

       That there is a fashion/hat/flight category is a beauty unto itself.
theleopard, Aug 21 2008
  

       Here's an idea - put all the beads in a medium they're neutrally boyant in. This might be an oil of some sort. Then shine some purple light on them. The purple beads reflect all the light, so remain colder than the rest which will absorb some. Purple beads sink, other beads rise. Remove the purple beads and repeat with orange light...   

       Then you need to clean the oil off, but that's hopefully a smaller problem.
Srimech, Aug 21 2008
  

       See [link] for some history of sorting small stuff.
csea, Aug 21 2008
  

       You could do all the sorting with sieves. Much cleaner.
ldischler, Aug 21 2008
  

       If you pour a mix of two sizes of sand through an hourglass, the sizes sort themselves into stripes. It's called a Hele-Shaw Cell. See link.
baconbrain, Aug 21 2008
  
      
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