A Shortcut for Bluing Gun Parts
In past issues of The Hobby Gunsmith we demonstrated ways to use rust to blue a gun at home. Rust was the original method of browning or bluing a gun part, but it is very slow for darkening smaller parts like screws or other small parts.
Comparing the results of the new room-temperature chemical bluing process to the more extensive rust bluing appear to be very similar in appearance. However; it will be some time before we can determine how well the chemical darkening process holds up under hard usage.
For this project we are going to use the Caswell Black Oxide process to darken the backing plate of the Dragoon cartridge conversion project and to fix some damaged screws.
We begin the project by examining the backing plate from the dragoon project. Some rust had formed on the surface and it needed a little sanding with 220 grit wet or dry sandpaper that we lubricated with unscented mineral spirits.
Figure 2 shows the backing plate after using the sandpaper to remove most of the surface scratches and pitting. The parts are ready to be dipped into the Black Oxide solution.
The solution comes as a couple of bottles of solution that is mixed with distilled water to form the oxidizing solution. The solutions mix quickly and are stored in a plastic bucket at room temperature. The kit comes with a container of sealant solution that is used to stabilize the finish.
We began by cleaning the part in either hot sodium phosphate solution or other suitable degreaser to remove any protective oils that may have gotten onto the steel part and might prevent the interaction between the steel and the solution.
I usually dip the part in a mild pickling solution made from hydrochloric acid, but that is not really necessary. The etches any smooth surfaces of the steel and gives the chemicals some bite.
The parts are dipped into the aqua colored solution and left there for about five minutes. Figure 3 shows the backing plate down in the solution. The part immediately begins to rust and then starts to darken into a black oxide coat.
The part is ready to be removed after about five minutes in the solution. It should be rinsed under running water and will have a black coat that should be removed for the most appealing finish. I use 0000 steel wool to burnish the part and bring up a nice shine that is similar to a rust blue finish.
I generally repeat the process of dipping into the black oxide solution about three or four times. After the first dipping, I find a shop towel can remove the surface material and prepare the part for either another dip in the solution or to be dipped into the sealing agent.
Immerse the part into the sealing agent illustrated in Figure 4. Leave the part in for at least five minutes to allow the solvent to soak into the finish and help protect it. Remove the part and allow it to dry. I like to then add a coating of gun oil to parts as an extra precaution.
We decided to treat some rusted and defaced screws to illustrate how quickly a damaged screw can be returned to a nice black color.
The screws illustrated in Figure 5 were polished using the same sandpaper method as the backing plate for the cartridge conversion.
When they were bright and shiny, they were dipped into the black oxide solution and then wiped with steel wool. After one or two applications of the solution, the screws look as they do in figure 6.
Figure 7 illustrates the backing plate installed in the approximate location on the frame of the Dragoon. The photograph does not do justice to the silky smoothness of the new finish. The color of the new finish is a blue-grey that allows some reflection from base color of the steel.
Those who have followed the Hobby Gunsmith from its earliest days will recognize the dragoon from the first issue, but may note that it has been nickel plated. The Dragoon parts were illustrated in the articles about electroplating that appeared in earlier issues.