Removing old paint from wood surfaces can be a difficult endeavour because the wood's porosity causes it to absorb much of the paint's adhesive. Fortunately, if you need to remove old paint from a brass doorknob, you will have a much easier time. Because brass is slick, hard and nonporous, it is not an ideal surface for paint adhesion. However, you must know the proper materials to use and the appropriate manner in which to employ them, or you may end up scarring the brass.
Remove the brass doorknobs, using a screwdriver.
Place the painted brass doorknobs in the plastic bucket.
Fill the bucket with enough paint thinner to completely cover the doorknobs. Allow the doorknobs to soak for 10 minutes.
Remove the brass doorknobs, and place them on a fabric dropcloth.
Scrape away as much of the loosened paint as possible, using a plastic putty knife.
Remove any remaining bits of paint, using steel wool.
Clean the brass doorknob, using a rag dampened in paint thinner.
The term "paint thinner" is often misused. It refers to white spirit, a petroleum-based solvent. Do not confuse white spirit for lacquer thinner or turpentine. Work in a well-ventilated area like a porch or an open garage. Protect your hands by wearing rubber gloves.
Many people claim that vinegar can remove paint from brass. While this may be true, the acids will also abrade the brass, creating pits in the surface. Do not use vinegar in place of paint thinner or you may damage the very surface you are trying to salvage. Do not use a plastic dropcloth in place of a fabric one, or the paint thinner may drip and pool up. Do not use a metal scraper in place of a plastic putty knife or you may scratch the brass.