In the past, removing paint from any surface was challenging because you needed to use abrasives or chemicals to strip off the paint. Now, new and safer products are available that allow you to remove paint easier with less fewer toxic ingredients. This is the best option for cleaning paint off a metal window frame because you can avoid making a mess on the glass by applying the remover more precisely. Make sure the paint stripper instructions state the stripper works on metal.
Wash the window frame with trisodium phosphate. Use a sponge to remove any cleaner residue or dirt. Rinse with water and dry thoroughly. This step will ensure the stripper adheres only to the metal, not anything left on the surface.
Use a paintbrush to paint a gel paint stripper onto the metal frame. Use a paintbrush that is slightly thinner than the window frame so you don't spread the stripper onto the window. Cover the entire frame with the gel stripper.
Wait from 2 to 24 hours for the gel stripper to work. The length of time will vary depending on the type of paint that is on the window frame and the type of stripper you are using. Consult the manufacturer's instructions to better judge how long the stripper should stay on.
Test a small area using a scraper to peel off a section of the paint. The paint will peel off in strips when ready. Peel all of the paint off the window frame.
Rinse the window frame with plain water to remove any stripper residue.