Once the red oxide converts to black (this will be obvious to the naked eye), it’s time to “card” off (remove) the excess rust. Wearing your gloves and using a soft wire brush, a wheel or degreased steel wool, you basically scrape the steel until all of the loose black rust is removed. Don’t use too much force or you might remove the finish that you’ve worked so hard to establish.
Now we re-coat the steel in solution, using a little less solution each time, and let it rust again. We don’t apply the solution more than once after the first cycle. When the rust forms, re-boil and re-card. This process is repeated anywhere from five to 12 times until you see the finish that you’re looking for.
Once the desired finish is achieved, liberally coat the steel in oil and let it sit for at least 24 hours.
The Verdict Once we got the water situation figured out, rust bluing went exactly as the instructions said it would. The result is a nice, satin finish and is attractive and durable. It takes plenty of time and effort, but minimal equipment cost. Rust bluing really is a finish that the home hobbyist can use to refinish steel firearms or components.