PS 2. Am leaving this here so as to not be a jerk, but in reference to above, the plastic bottle thing is right! Glass doesn't work because (I *think*; I am going off memory completely) it blocks more of the spectrum than plastic used in water bottles, and I think heat + ultraviolet light is what provides the sterilization. And I would very much agree that plastic leaching is a concern for people who are not very worried about their access to clean water.