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