Pure water and why upper glass dries clean
Tap water in Naples carries dissolved minerals, and inland well water carries more. Leave a drop to dry on glass and the minerals stay behind as a spot. Pure water has been run through filters that take those minerals out until there is essentially nothing dissolved in it. Fed up a pole to a soft brush, it scrubs the glass loose of dirt and then rinses it, and because nothing is left in the water, nothing is left on the glass. It lets us clean second-storey windows and the high glass above a lanai from the ground, with no ladder leaning on the stucco and no one standing on the cage frame.

