Make a simple water purifier with 2 soday bottles and a copper wire

Pretty nice build.  Basically the one bottle evaporates the water to help with purifying it.  Apparently the coppyer wire also helps here (not sure I understand that bit fully).  But this does seem too work.  2 changes I would do, use glass (little leery of using plastic here).  The other is a better shade for the 2nd bottle.

http://www.instructables.com/id/Huaico/?ALLSTEPS