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