bubble bags - Explanation

obviously they are for hash.
BUT
how do they work,EXACTLY?

the first screening is to remove plant matter correct?

then what?
the mesh gets finer to screen untill a better more refined product?

but what of all the other stuff that is left over in each screen untill you get to the final refinement?

.....lost

thanks
Later

http://www.bubblebag.com/products/bubblebags.php

Read everything there.