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