I've been following this thread, so I had to give heat bluing a try. I watched two videos by Larry Potterfield, one titled Flame Blue (
), and the other titled Nitre Bluing (
). Using equipment on hand (torch, hemostats, motor oil for quenching), I tried it on a couple of cheap machine screws, and here is the result: [Linked Image from i.ibb.co]

I'm satisfied with the results given that this was a first try. I expect I could do better with more practice. My biggest challenge was catching the color change where I wanted it. The screws heated up so fast that when the color change started to happen it was hard to get them into the quench fast enough. Again, with practice and patience I could do a little better.

A couple of things I'd welcome input on - when doing this with heat is the durability of the finish any different than doing it with nitre salts? Similarly, what is the overall durability of the finish? I realize it polishes off easily. Does the finish bring any additional rust protection? Any input is appreciated.