here you go, if I am not wrong this is from Dave, I saved it,,,,,,,,,,,,,,,,,,,,,,,
Don't let anyone tell you that browning, bluing, or darkening the cast textured surface of the lock is in any way historically correct. It is an immediate give away that the gun is modern made. No matter how you color it, file, sand, and polish off the cast texture. The photos below show how I finish gun locks. Locks in the 18th century were usually made from wrought iron and were case hardened. A color case as shown in my last photo is appropriate for some 19th century American guns and some English guns made after about 1780 or so. In America, any colors from casing were usually polished off. Locks were either polished bright or colored by temper bluing and charcoal bluing. Rust browning or bluing was not used in America until almost the 19th century. The late flint lock on the third gun down is charcoal blued, the others not polished bright were temper blued or temper bronzed. It is easy to polish a lock bright. Just use files, polishing stones, and/or wet sand paper. Burnish with steel wool. Do not use a buffing wheel because it will round corners and dish out screw holes. When using sand paper always back it with a file or wood to keep from doing the same thing. For temper coloring, polish the parts and then heat slowly to 490 degrees F to get a bronze color or 600 to get a blue. You can do the bronze in a kitchen oven. Leave the part for at least 30 minutes at temp. For blue, you can use a torch but a casting oven is better. Regardless, heat the parts for at least 30 minutes and then air cool. When just cool enough to touch with dishwashing gloves, rub the parts with rottenstone dipped in boiled linseed oil. That will deepen the color and also the oil will bond with the warm metal. For charcoal bluing you need a real heat source. I have a casting burn out oven with programmable temperature controls. The parts are packed in charcoal within in a steel box with lid. Then the box is heated to 900 degrees F for 3 hours. It is then let cool and the still warm parts are removed an rubbed with rottenstone and linseed oil. Then they are again degreased and packed in charcoal for another heating cycle. Two cycles is usually enough and the parts rubbed with rottenstone and linseed oil after the second heating. This gives a deep and durable blue hat was often found on English guns and occasionally on 18th century American guns.