I recently moved into a new house. Several of the exterior vinyl
windows have these strange fingerprints on the outside of the upper
pane just above the meeting rails. I've tried cleaning them with a
razor blade, soap and water, Windex, Simple Green (full strength), Goo-
Gone, Goof-off and Turpentine. With tons of elbow grease, I'm able to
get the fingerprints off - with no one product obviously dissolving
whatever the fingerprints are made from. Still, when I go to clean
the window afterward, just spraying a soapy solution to squeegee, you
can clearly see where the fingerprints are - even though the window is
mostly clear. I have 19 windows to go and dread the thought of having
to spend 15-20 minutes on each getting these prints off and even then
- not really getting them all the way off. Any ideas what they could
be and what would dissolve them without damaging the glass or windows?