Charcoal bluing hardware

[dave_person]

Hi,
I am learning to charcoal blue the steel hardware on the late flint English rifle I am finishing up. I did a bit of experimenting and found that a temp of 790-800 degrees worked best. I polished the breech with stones and oil up to 800 grit. I degreased it intially, and packed the breech, which is made of 4140 steel, in a metal box with bone charcoal. I heated it to 790-800 for 1 hour in my oven, took it out, let it cool a bit, then removed the breech and carded it with light oil and pumice stone. At first I did not use the oil but simply the dry powder, but I found the oil seemed to darken the blue. I then wiped it clean and returned it to the pack for another cycle. I did 5 cycles to get the color you see. I then let it cool a bit, wiped it clean, and then coated it with tung oil while still very warm. In a day or so, I will buff it with a canvas rag.

dave

 

[hanshi]

That is a beautiful blue color that you ended up with. I like it much better than the blue finishes that look more black than blue.

 

[George]

Hi,
I am learning to charcoal blue the steel hardware on the late flint English rifle I am finishing up.

Dave, in his Essay on Shooting, 1789, Wm. Cleator discusses charcoal bluing and has this to say:

"Formerly, barrels were coloured by exposing them to a degree of heat which produced an elegant blue tinge; but as this effect arises from a degree of calcination taking place upon the surface of the metal, the inside of the barrel always suffered by undergoing the same change. This, therefore, added to the painful sensation excited in the eye by looking along a barrel so coloured, has caused the practice of blueing to be disused for some time past. Instead of it, barrels are now browned, as it is termed."

Do you understand what he's talking about, or have you seen anything such as he describes? As I understand it, his 'calcination' is what we would call oxidation.

Spence

 

[dave_person]

Hi Spence,
Yes, I believe I understand Cleator's point. Prior to wide spread use of acid mediated rust bluing and browning, barrels were temper blued and charcoal blued. Temper bluing was just heating the metal to 575-600 degrees and letting cool. The blue was vivid but did not last long. However, the temps were well below that which would cause scaling of the metal. Charcoal bluing used much higher temperatures and a relatively O2 restricted atmosphere within the charcoal pack to create a deeper, long lasting blue and the charcoal helped inhibit scaling at the higher temps. However, heat control was not what we have today and there likely always was some risk that scale would form in the bore of the barrel, potentially ruining its shooting quality. Eventually acid-mediated rust browning replaced charcoal bluing because it had little potential to damage the barrel, was long lasting, and rust resistant. Heat blued barrels were shiny and I suppose heat waves and reflections off them affected sighting. Browning also was better in that respect. In my case, the barrel of the rifle is rust browned to a nice warm reddish plum brown and the charcoal blued breech with inlayed gold looks really nice in contrast.

dave

 

[Phil Coffins]

Dave, that's quite handsome. I played with charcoal bluing a bit and after a couple of test pieces did this pistol. I had already made grips and color cased as needed then did the bluing with wood charcoal. My method was polish and degrease then pack in the wood charcoal. Held at 800 f for 3 hours then allowed to cool in the pack. When cool the dust was blown off then machine oil applied and hung up to cure for three days. A simple wipe down then assembled it.
The test piece and pistol.
IMG_0241 by Oliver Sudden, on Flickr
IMG_0400 by Oliver Sudden, on Flickr

 

[dave_person]

Hi Phil,
That is very nice. Probably your longer heat soak was the same as my multiple cycles. I was going by some old instructions that recommended the oil and abrasive carding. Here is another photo showing the blue color.

dave

 

[Kansas Jake]

Phil and Dave, the work you do leaves me in awe.