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