Things You'll Need
Old credit card (or razor)
Mildly abrasive cleaner
Vinyl window frames are designed to be mostly maintenance-free, since most dirt and grime do not adhere to vinyl. Even paint may not always stick to vinyl, but when it does, it really stands out against the whiteness of the vinyl. Removing fresh paint is as easy as wiping it off, and maybe rinsing the area, but after the paint has set, you will need to carefully scrub it off without damaging the vinyl underneath.
Place the edge of the plastic credit card against the beginning of the paint. Press down and scrape the card over the paint stain to remove as much as you can. If the paint hasn't been there all that long, it should all come off. You can use a razor blade instead of a credit card, and you might get better results, but be careful that you don't cut your vinyl.
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Apply a bit of a mildly abrasive cleaner, like Soft Scrub, Ajax or Bon Ami, to the sponge and apply it to any part of the paint stain that remains. Wait a few minutes before continuing.
Use the scouring pad and scrub the vinyl surface where the stain is. Don't try to dig in with the scouring pad. Just try to scratch the surface of the vinyl.
Use the sponge and water to clean the area. The paint should now be completely removed from your vinyl window frame.