I don't usually do the cleaning on the exterior of the vinyl windows, that's something DH has always done, as it's difficult for me to reach it all. So, last night, I decided to go out and do the windows, before I put up new curtains, since DH is not here right now. I opened the one on the door side, spread it all out and sprayed with vinyl cleaner. To my shock, there was solid black grime coming off it. Not brown or tan, but dark solid black like coal. Since we live in Florida, I was confused about this. It took about 1/3 roll of paper towels to get it all cleaned. We don't have coal mines or coal dust here, just tan sand. So, finished up that side and opened up the rear window to start on that. To add to the mystery, that side only had tan/brown dirt on it. A few hours later, it finally dawned on me how the front side window got blackened. I'm just curious if anyone here comes to the same conclusion. What do you think?