We recently had the windows redone in our 1920s-era condo and, in the process, had a wall opened up to reveal windows that were walled off from the inside some time in the 30s. However, the grime on the exterior of the windows will not come off (action shot below). We've tried:
- Goo Gone acetone
- Soap and vinegar
- "Magic Eraser" sponges
Whatever substance has bonded itself to the windows, it's not just dirt. I'm guessing something like tar and soot perhaps? Regardless, I'm wondering if folks have encountered similar challenges and how they've tackled the issue.