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