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