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