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