Charcoal Bluing

[NSBrown]

Instead of filling the bore with pulverized charcoal when heating the barrel, would it work to use a wooden dowel close in diameter to the bore and the length of the barrel? Would this work to eliminate oxidation in the bore during the charcoal bluing?

[Long Ears]

I'm lost, sooo wouldn't the dowel burn up in the fire? Try heating a barrel in boiling water with both ends plugged. The air inside expands and presto, a cork gun like when we were kids! Either way your barrel is no longer plugged. I believe a couple of the reasons you pack the barrel with charcoal is to keep it from developing scale in the bore and to keep even temperature across all surfaces to prevent warping. I'm sure others will help if I'm way off base with what you are asking. Bob

[FALout]

I haven't done a barrel with charcoal bluing, but I would think that the filling of the barrel with pulverized charcoal is to prevent oxygen from being in the barrel.  A wooden dowel is only going to provide fuel and oxygen while heating the barrel.

[Acer Saccharum]

the dowel will off-gas water and acids...you'll probably end up with a horribly pitted bore. Dunno, really, what the end result will be. Try a test on a piece you don't care about.

[Mark Elliott]

The charcoal is just to keep air away from the bore so that you don't end up with forge scale (which is basically what a charcoal blue is) in your bore.   You can buy jars of powdered charcoal in a good art supply store.   I think 1-2 jars should do it.   I want to charcoal blue the barrel on my chunk gun, but I really don't have a safe place for the charcoal pit.   By the way you don't really need the charcoal pit if you have a heat treat oven big enough for a barrel,  which I don't.   Basically,  if you heat steel till it just glows red in the presence of oxygen, then you get that nice blue-gray oxidation on the surface.   

[kutter]

Charcoal bluing is the oxidation color the steel gets at about 850F,,which is the temp the charcoal embers cook at. The charcoal gives off CO, which keeps the air (oxygen) away from the surface.
If you're getting a heavy heat scale coating, even if it looks nice,,the temp is too high to call it charcoal bluing.
A very fine line between the two.

Nitre blueing works the same way,,the fact that the part is immersed in the molten nitre keeps it safe from the oxygen in the atmosphere. Run the nitre up to 830/850F and the results look amazingly like charcoal blue.
No heat scale,,just the oxidation color of the steel at that particular temp.
I did many of the small parts on restorations in nitre at high temp and left the bbl and any larger parts that needed the charcoal 'blacking' for the real thing. To difficult for me to handle tiny parts at those temps and properly burnish them w/o either damaging the part,,or me,,or both.

Any uneven coloring that does start to show up in charcoal bluing can be burnished out and built up to a uniform appearance though just that, burnishing.
The old methods suggested 'tow' w/ lime as very mild abrasive. Then a coating of (whale) oil and back into the charcoal.
The oil smokes but does not catch fire, further protecting the surface from atmosphere contact.
The oil can give you some problems if it's not applied evenly or it's put on too heavily. Like everything else, it takes some practice.

The process is done over and over till the results are viewed as complete.
It's not a one step process like nitre or heat bluing though there are a couple of quicky methods around for small parts.


Burlap and sisal along with lime or even talc make for good burnishing. They don't scratch the surface finish but will even things out.

No need to plug the bore or do anything special with it. When you're done it will be blued also of course and unless you've gone through the effort to  run a dry brass brush through the bore on each step,,the blue will be a bit spotty. But there shouldn't be anything that a normal bore cleaning won't remove at the end of the process.

All the firearms mfg'rs used the process till the gas fired rotating furnaces came about in the early 1900's.
Labor saving devices is all that they were. The continuous rotating drum gently dumped the fine charcoal over the parts wired inside,,this acted as the burnishing action that was done by hand before. The temps were the same but better controlled of course, A closed atmosphere where oxygen is pushed out and kept out by the smoke from the oil and the CO from the charcoal.
The rotating furnace process had the propietary use of a certain oil in the char mix. But some users of the furnaces used nothing more than linseed and other common oils. The hardward business was a big user of it. Remember when all those nuts, bolts and washers were 'blued'..
Using different oil will alter the color of the finished blue surface color.

Look at any Colt firearm made before about 1912 and you'll see the labor intensive charcoal blue finish.
The polishing was and still is the secret if there is any to the brilliant and rich look of it.
It's dangerous work, becareful handling 800+F degree pieces of steel and burnishing them down.

[Mark Elliott]

Thanks Kutter!   That was very informative.   I learned something useful.   I do have a question.   How do YOU handle a hot barrel to burnish it?     I can't really think of a way to safely handle a 46" 12lb hunk of steel that is 850F.    I would have just used some black iron wire to lower it in and pull it out of the charcoal, but you couldn't really handle by that to burnish it.   

Mark E

[kutter]

You place a very smooth steel rod through the bore that is long enough to extend out each end a few inches.
Put an 'eye' on one end, and  a screw on eye' on the other.
Through those eye attachments you can handle the barrel into and out of the char.
I used T handled hooks made out of steel rod. I didn't want the thing swinging around on a wire.

It's takes some practice even then as sometimes you can reach the length of a L/R bbl,,but to do that put's your face and body mighty close to it. You need the hooks or what ever you use to be long enough to be able to comfortably lift it and carry it but still keep it at a safe distance from you.
You'll feel it when it gets too close!

Next you need something to set it down on to work on it.
Sturdy but simple Y shaped supports placed at the right distance to set the barrel down between them.
They must be sturdy and secure from movement..

That long steel rod through the bore is what sets on the supports,,not the bbl itself.
Also, the distance the rod extends from the bore on each end is minimal where the support rests.
That is important in the burnishing step.

It's important to do some pre-planning and dry run to make sure everything is ready and set up right before the real thing takes place. You're not going to be adjusting the supports later while hanging onto a 800+F degree bbl with a couple of hooks.

Now that the bbl is set down on the supports, get right at it to burnish it down.
It's secure in position horizontally by it's own weight and the fact that it can't slide back and forth on the rod because of the spacing of the secure supports.
Those supports are placed to be between the ends of the bbl and those 'eye' fixtures on the ends of the steel rod so the bbl can't slide back and forth.

So you're going to rub this thing down but how do you turn it ,,or keep it from turning,, as you work...

The barrel pin lugs on the L/R bbl are handy. They must be secured in dovetails,,not soldered on obviously.
A small vise grip plier is good for the chore.
Attach it to one of the lugs,,pick one that suits you and leave it attached while doing the entire burnishing session.
Use it to hold and turn the bbl as you work it over. Smooth the jaws of the pliers if you don't want any marks impressed into the lug and you may have to run the drill through the hole when you're done if you turn the metal over a bit.
Keep using the same attaching point,,makes for only one spot to clean up if needed at all.

Doing any parts with this method means you have to make some sort of handle or fixture to be able to carry the part around and also be able to work on it w/o endangering yourself.
A bit of originality comes into play in figuring out how best to do that sometimes. Along with a box full of seldom, if ever to be used again odd shaped widgets that only you will ever know what they were made for.


Burnish with canvas. Clean shot bags are (were) pretty good, but don't use the printed side of the bag against the finish. The older shot bags in the 60's and 70's were sturdy canvas,,now the stuff comes from where-ever in more of a medium weight cloth bag material. That may work too, but I've never tried it.


 Burlap works good. I guess you can still find 'tow'. I think it's jute plant or something like that. Some of it is already oily and may be all you need to work with.
All you're doing is trying to even up any discolored spots or areas where some contamination may have gotten on the finish. Kind of the same things you do when carding rust blue and you fine those annoying small spots that ruin an otherwise nice finish.

Use a big enough piece and  heavy gloves to avoid getting burned. I used to use welders gloves doing this and were pretty good. You could still feel the heat through them if you were touching something you probably shouldn't be. Probably better stuff around today.
If you do this enough,,you will burn yourself most likely.

Have lots of burnishing mat'l available. You'll be dropping it from the heat or clumsiness of the gloves. Don't be tempted to reuse it as it may pick up a tiny bit of grit you don't want,,and you may put some interesting  lines in the metal finish with it if you do.

Some burnish with the material alone. Some use with lime, talc, or other very fine polishing powder to further enhance the look.
The application of a very thin coating of oil after the burnish is done is part of the process,,though it will work w/o that being done I've found.
 You don't want much and the hot metal will thin it and it'll run all over the place anyway. So if you use it,,don't get sloppy with it of it's just make for more burnishing work the next time around.
This always gave me mixed results. Maybe it was the type of oil,,I tried many.
My best results were applying the oil with a cloth dampened with it. Almost like wiping down the part after cleaning the gun to protect from fingerprints.

Do all of this as quickly as you can,,but don't do a poor job of it either.
It gets easier the more you do it and like rust bluing, you find little tricks that seem to work for you. Those same tricks may not work for someone else trying the same process, but that's just the way most of these metal finishing processes are. Case color hardening is no different. What ever works for you.

Back into the charcoal for another heating.
Use the hooks to lift the bbl off the supports and place it back into the coals. Rake the coals over the bbl. Keep it covered at least  an inch deep all around. A little more is even better. Carefull you don't scratch the bbl when raking the coals around.
Add charcoal to the fire to keep it up. But don't add it to the top of the pile directly. Off to the sides to allow it to get going and burn down some. Then pull the coals on to the pile if needed. Prepare the bed with new while the bbl is out being burnished if needed.
You want to be able to set the bbl right back down into the bed, cover it back up with the coals and let it alone.
It's an inexact science for sure.

Maybe 15 to 20 minutes for a session in the coals. Longer won't hurt but the oxide coating can start to build up  too much and getting it evened out is more difficult then.
It can depend on how long it took you to burnish the last coating and how much the temp has dropped too. The heavy bbls stay pretty hot though.

I know some do this charcoal bluing method in one long sustained cook,,then they are done. No burnishing.
It can be done that way, and holding the temps right, keeping it covered, ect will give you charcoal blue.
It's easy to let it get away from you that way. If it gets too hot and/or the air gets at it you end up with a heat scale coating that while not unattractive, it's not charcoal blue.
The real fine finish is done by building and refining multiple oxide coatings.
Maybe that's something people don't even want on a L/R,,I don't know. But that's the method I always did  in the restoration business. But that was 95% cartridge guns.

Anyway,,,Keep building the finish up till it looks right for you. It may take 5 coatings,,it may take 10. It may look great at 10 so you do one more and you get something on it that leaves a big discolored mark. You burnish that out over the next couple of coatings and bring the color back up to where you should have stopped at 10 like you told yourself to do.

You'll be tired when you're done.

Small parts are way easier.
I think the only commercial cartridge rifle that had it's barrel charcoal blued was the Henry rifle.
Might be others, but I can't think of any. It was the mainstay receiver, small parts and handgun  bluing finish process for most all the manufacturers till about 1911/12.

Hope this helps..

[Mark Elliott]

Thanks Kutter!