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