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