[GSBN] Help us help in Haiti

[Bruce King]

Happy New Year, baleheads.

We have a lot of soil in Haiti that is rich in both clay and silt.   
Easy enough to separate the sand and gravel, but we haven't figured  
out a good way to separate silt from clay.  So far we've tried:

1) Asking nicely
2) Offering every silt particle a chance to win a Hawaiian dream  
vacation if it separates itself from the clay
3) Telling the silt that if it just leaves quietly now, no one will  
get hurt
and, getting really hardball,
4) Hanging a few "example particles" of silt by their silica crystals  
in the public square, with warning notes attached.

Still no luck!  Anyone have a good low-tech field method for separation?

Thanks,

Bruce "Hang 'em High!" King