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