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