when you smoke hemp  it leaves a residue 
 tar   inside  the   machine,   which  is 
 extractable  with  the  help  of a metal 
 rod. be  wary however, that the hemp tar 
 is  not as viscous  as  you may think... 
 it'll  quickly get on your  fingers  and 
 boobs... and it's hard  to get off. very 
   sticky business indeed. most people    
 just   get   rid   of   their   machines