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