We use a water-fed pole system with hot, purified water. The water goes through a filter that strips out everything dissolved in it, the chalk, the minerals, the lot, until there’s nothing left in it but water.
Ordinary tap water dries and leaves behind everything that was dissolved in it, which is what those white spots and streaks actually are. Pure water has nothing to leave behind, so the glass dries clear on its own with no cloth, no detergent and no smears.
Surrey is a hard water area, so this matters here. If somebody cleans your windows with a bucket of tap water, they are rinsing your glass in dissolved chalk and then letting it dry on.
