I wanted to give charcoal bluing a try, I found this recipe in Clyde Baker's book "Modern Gunsmithing"
It reads:
An old English gun maker gave me the following which I have seen him use to produce very fine work, although I have never used it myself:
Make a boxy of heavy sheet iron large enough to hold the largest part to be blued. It is not necessary to rivet or weld the box, merely fold the corners. Fill it with pulverized wood charcoal in lumps about the size of a small pea, and heat in a furnace or large forge until the charcoal is partly burning throughout, but not quite redhot. Attach an iron rod at least two feet long to the gun, and bury it in the glowing mass, allowing the rod to stick out for handling. In 5 to 10 minutes, lift out and examine it. If the color has started, take a large wad of clean cotton waste or tow, dip it into dry powdered lime and rub vigorously over every part and work fast. You may be fooled at the first bright blue that appears. This is merely a "tempering color" and must be disregarded. It will not wear, and it is not the blue you are after. Continue the treatment until a deep blue-black similar to that seen on Colt revolvers has developed. Let cool in the air (do not quench) then apply any good light gun oil.
Oops this got submitted before I finished it
returning to Clyde Baker's book
The process may be repeated a second time if desired, usually deepening the color. The parts must of course be cleaned of all this by applying a mixture of chalk and water, letting it dry on the gun, then brushing it off.
A variation of this method was at one time used by Smith and Wesson, except that the gun was rubbed with oily waste instead of lime. Either method required considerable skill and experience, but the results fully justify the effort."
I had looked through the internet other discussions of this, and thought I would give it a try at home. I had a trigger guard that I wanted to reblue, a floor plate and a ramped front sight. I polished the portions of the trigger guard and floor plate that I wanted reblued to 600 grit and degreased them in acetone.
I smashed up some charcoal briquettes and put them in an old roasting pan. But that on my gas grill and cranked up the burners to high and waited, my grill may not be the most powerful, I reached a high temperature of 550 F. At that point, the charcoal at the surface was turning to ash and would glow if a breeze hit it. Not quite the description of the coals in Clyde Baker's book. But I gave it a try anyway. I submerged the floorplate and front sight in the charcoal and pushed the bottom of the trigger guard into the charcoal and used a trowel to cover as much of it as I could, the magazine box stood out of the charcoal. Every 15 minutes or so, I would pull the parts out and rub them with a cotton cloth dipped in rottenstone. Here are the results.
The quick release lever was fire blued. I was really pleased with the results, it could be done without much in the way of specialized equipment. I will definitely do it again. Next time, I will wait until I have a number of parts to blue, use more roasting pans and build holders for the parts. I was fishing them out with tongs and holding them with tongs while rubbing them with rottenstone. If the tongs slipped, I would get scratches.
