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