The important thing to realize about bluing is, it is rust. Bluing is an iron oxide. Anything that removes rust will also remove bluing. Iron oxides are complex mixtures and can be formed by rusting, heat tempering, and chemical baths. The nasty loose rust we all despise is mostly ferrous hydroxide. Heat and/or drying out will result in a mixture of ferrous and ferric iron oxides.
Classic browning uses no heat other than room temperature or a low heat in a rusting cabinet. The brown can be given a darker color more quickly by steaming the parts or using boing water on them. The loose rust is carded off and the process repeated until the desired darkness is obtained.
Heat or "temper blueing" results in "magnetic oxide" or ferro-ferric oxide. Most of what I understand about the process comes from "Firearm Blueing and Browning" by R.H. Angier that was written in 1936 before much of our modern understanding of quantum mechanics
. If you want to really understand the process you can still find the book.
Angier does give a description of the Smith and Wesson temper blue provided by Major D. B. Wesson. That process, involves heating parts in special tumbling drums. The parts were mounted on armatures and tumbled with bone black and Carbonia. The drum turned in one direction, the parts armatures in the other. This produced the famous Smith and Wesson Blue. This heat color is a Ferro-Ferric Oxide heavy in the Ferric Oxides.
The Ferro-Ferrric oxides are harder and tend to produce thinner coatings than the common ferrous oxide rusts. In classic browning, which we use on muzzle loading rifles and twist shotgun barrels, the rust brown is carded of, a fancy term for soft wire brushing, leaving the darker harder oxide behind.
All blues and browns will absorb oils and waxes and darken when they are applied.
Oil or wax will deter oxygen and moisture in the air from reacting with the ferro-ferric oxides in the blue. No blue is truly stable in the presence of oxygen over a long period of time.
The quality of the finish is dependent on two things, first, the polish of the basic part before the bluing is done, and second, the corrosiveness of the rusting or heat tempering process used.
Under every layer of rust there is a darker layer of ferro-ferric oxide. The ferro-ferric layer is thinner and slightly harder than the "nasty" loose rust. However the ferro-ferric layer will readily come off with harsh abrasives. Metal polishing techniques that will shine up steel will remove the bluing.
My experience in doing the old fashioned browning process is that 0000 still wool can be used only with extreme care. Bronze wool is better but care must also be exercised. Burlap and oil work well on finished parts. White or green 3M abrasive pads work well, I prefer the white although they are much slower. The white pads will remove rust and leave a patina.
Any of the abrasive pastes, like simichrome, are good for polishing chrome or steel, risky on blue.
Coarse linen tow, or unravelled hemp rope, also make good rust removal tools with a little oil. The goal is to remove any loose rust from the surface and out any pits while leaving the dark patina behind, and not disturbing the original finish. If you remove the pits, you remove the blue.
Classic browning uses no heat other than room temperature or a low heat in a rusting cabinet. The brown can be given a darker color more quickly by steaming the parts or using boing water on them. The loose rust is carded off and the process repeated until the desired darkness is obtained.
Heat or "temper blueing" results in "magnetic oxide" or ferro-ferric oxide. Most of what I understand about the process comes from "Firearm Blueing and Browning" by R.H. Angier that was written in 1936 before much of our modern understanding of quantum mechanics
. If you want to really understand the process you can still find the book.Angier does give a description of the Smith and Wesson temper blue provided by Major D. B. Wesson. That process, involves heating parts in special tumbling drums. The parts were mounted on armatures and tumbled with bone black and Carbonia. The drum turned in one direction, the parts armatures in the other. This produced the famous Smith and Wesson Blue. This heat color is a Ferro-Ferric Oxide heavy in the Ferric Oxides.
The Ferro-Ferrric oxides are harder and tend to produce thinner coatings than the common ferrous oxide rusts. In classic browning, which we use on muzzle loading rifles and twist shotgun barrels, the rust brown is carded of, a fancy term for soft wire brushing, leaving the darker harder oxide behind.
All blues and browns will absorb oils and waxes and darken when they are applied.
Oil or wax will deter oxygen and moisture in the air from reacting with the ferro-ferric oxides in the blue. No blue is truly stable in the presence of oxygen over a long period of time.
The quality of the finish is dependent on two things, first, the polish of the basic part before the bluing is done, and second, the corrosiveness of the rusting or heat tempering process used.
Under every layer of rust there is a darker layer of ferro-ferric oxide. The ferro-ferric layer is thinner and slightly harder than the "nasty" loose rust. However the ferro-ferric layer will readily come off with harsh abrasives. Metal polishing techniques that will shine up steel will remove the bluing.
My experience in doing the old fashioned browning process is that 0000 still wool can be used only with extreme care. Bronze wool is better but care must also be exercised. Burlap and oil work well on finished parts. White or green 3M abrasive pads work well, I prefer the white although they are much slower. The white pads will remove rust and leave a patina.
Any of the abrasive pastes, like simichrome, are good for polishing chrome or steel, risky on blue.
Coarse linen tow, or unravelled hemp rope, also make good rust removal tools with a little oil. The goal is to remove any loose rust from the surface and out any pits while leaving the dark patina behind, and not disturbing the original finish. If you remove the pits, you remove the blue.
