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