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