naptha takes forever to evap and most naptha has some contaminants that will make the end product taste bad. alcohol on the other hand evaps quick and its contaminants are just water and other alcohols or ketones used as adulterants that also evap just as quick leaving behind a relativly pure extract. think of it this way say you pulled some jungle with xylene, it just evaped and is as 'dry' as it is going to get. would you smoke it right away or do a heptane/alcohol cleanup on it to get out lye, bark juice and whatever else is in there. i suppose i could try evaping the naptha but i think most of that would oxidize or react with the air somehow or the taste would be ruined.