The process of Bluing (otherwise known as Black Oxide) starts with the firearm being completely disassembled and cleaned.
Depending on the desired finish it will either get polished or Media Blasted. A lot of the “Black Guns” are media blasted then dipped in Black Oxide.
The finish comes out a Matte Black. This is also a good finish choice when a firearm is very rusty. In this case, the media blasting will not only get rid of all the rust but it will also help blend the metal so the damage (pitting) caused from rust is not as noticeable.
If the desired finish is a more glossy finish then the metal is polished multiple times using different grits starting out at 90 grit and ending at 400 grit.
The metal at this point almost looks chrome plated. The shiner the metal before dipping the better the finish will look when completed.
Due to the amount of polishing that is required to get a glossy finish it is usually hard to give an accurate quote without seeing the firearm.
The bluing process that Under Ground Gun Works does is called HOT blue.
Once the parts have gone through the required prep stages, they are then dipped in a heated cleaner bath solution. This removes any grime or grit left over from the blasting media or polishing compound as well as all oils from handling.
The parts are then moved to the bluing tanks which are heated up to 285 degrees. The parts soak in there for 20-30 mins then move to a rinse and oiling station. Once they are oiled they need to cool down for as long as two hours. Then they can be reassembled.
The bluing process does not affect tolerances. The process is more of a penetration coating then a layer coating like paint.
Metal is the only item Under Ground Gun Works can blue - within the following exceptions: