Gun Bluing...at TechShop Yo.

Metal
Sandblaster, (TechShop) 
Cotton Rag, cotton balls
Gun Blue
Small Glass Dish
A sink with Running Water
Gloves
Clear coat or wax
Steel wool 000 / Scotch Brite
Spray Booth (TechShop)
Respirator

This is a piece of metal that I gun blue last year, but I was not happy with the clear coat. I have learned over the years that it takes a lot of trial and error to get to the look that you are looking for with gun blue. I like when you have some of the red and green streaks.

The method that I use to clean the metal is sandblasting, can also use pure alcohol or naval Jelly. Sandblasting forces large amounts of sand against the metal surface, breaking down the rust and some metal into fine particles that separate from the surface. When sandblasting, make sure that you a consent pattern moving across the metal. The Naval Jelly is an acid that breaks down the rest. You want to get any old bluing off the metal along with the oils from your hands. When you are done with clean process, do not want to touch the metal. The oils from your hands will leave marks on the metal. They may not show up for a year or so.

I have all of my supplies laid out by the sink before I start to work. The heat gun, small dish with gun blue, cotton balls or cotton shirt cut in to smaller pieces. Put on gloves. With the heat gun, heat the metal. You want the metal warm to the touch, you should not have to wear work glove to handle that metal.  If you have an oven handy you can heat the metal in the over, set the temperature to low/warm. How long you have to keep you piece in the over will depend on you size of you piece.

With the small cotton rag dip into the gun blue and wipe on to the metal. I try to go in a pattern. Moving across the metal, you may have to re-dip the rag or cotton ball. When doing a large surface have some extra per cut cotton rags so you can grab a new rag when needed. This is true with steel wool as well, but the steel wool will oxide and turns black. I like the look when it has some green, purple and blue streaks threw out the metal. Don’t let the gun blue puddle or run; it will be much darker than the rest of the metal.
In between coats lightly sanding with 000 steel wool or a scotch brite, if you sand too much you will sand of the gun blue that you applied. Rinse off with water, the water will stop the oxidation. After the last coat of gun blue I still walk out the water with a heat gun.

For the finish I use matte clear coat, which I pick up at my local hardware store. Before you start to spray. Make sure that the spay booth is on along with  your respirator. Start to spay your metal working back and forth from one side to other and over lapping as you move along. When the clear coat is dry you can pick up the metal.

And you are done.