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