I think my windows are dirty on the inside. I didn't think it was possible but it's the only explanation. And it doesn't seem too far-fetched, considering they are the cheapest, whitest, vinyliest windows that almost no money can buy. Thus I believe the seal has broken and schmutz is accumulating between the double-hung panes. After taking a bunch of window-cleaning advice under advisement and still being unable to get the windows clean, this can be the only explanation.
I promise never to write so much about window cleaning again. But when you've spent as much time on it as I have over the past 5 days, you start finding really dumb stuff fascinating.
The result of all my work: slightly cleaner home and a big scab on my head from a tilt-in window that smashed me on the head. I'm trying to convince people that I received the injury while head-butting a Nazi skinhead at a Judge show, but I'm pretty sure they broke up when I was still in high school. Plus no one would believe it anyway.
Next exciting project: cleaning the basement! Well, yes, but there's an interesting reason for fixing up the cellar: my triumphant return to screenprinting! More on that once i move all the cat shelter materials off my worktable.
Extra reference: Paradise Exteriors – Hurricane windows.