i like the colors created by case-hardening... i was told by a gunsmith that there is a difference between case-coloring and case-hardening..... i know that the hardening process is a heat treating process.. but thats about it...so whats the difference???.. can a receiver (like a 1917 remington enfield), be case-colored???... or does it need to be case-hardened???.. thanks...

This is a popular topic.

From what I have gathered, the difference between the two is that the coloring process produces colors, while the other does not. Both processes harden the surface of the steel to the same effect to a depth some thousandths of an inch.

It's my undersdtanding that case coloring is a very thin case (like .001 or so) and is very different than case hardening which (in some circumstances) can reach .06 deep and more if one decides to include induction hardening as case hardening! (typically case hardening is .005-.015 deep)

Case hardening is a well documented science used to heat treat low carbon (mostly) steels like ball bearings and literally millions of other components. Almost all sizing dies for reloading are case hardened as are case trimmers and many deburring tools.

The artists that produce blues, greys, and shades of yellow in case coloring are not at all interested in the hardening process but the cause of colors.

Hopefully someone that actually does case coloring will post the process.....it seems to be a trade secret however as to how they manage the colors.

Just remember that 1917 US Enfields, and their companion P14 British rifles, were made from 3 ½% Nickel steel and were truly heat treated throughout rather than case hardened like early 03’s and Mausers made from soft low carbon steels.

If I were you I would contact someone like Doug Turnbull who does this stuff for a living and see what he says about applying a color case to that type of steel. If anyone would know if it is practical or advisable he would.

I have read the color process is as follows:

The part is packed in a chamber (the case) surrounded by charcoal made of bone and leather; some recipes call for cyanide added. The case is heated to a determined temperature, and allowed to soak in that heat for a specific amount of time. Then the case is removed from the heat, and emptied into a quench of water that has been charge with air or oxygen, I don't know which. It is the air or oxgen present in the water that produces the colors- stagnent water, or perhaps another kind of quench, produces the hardening only.

I don't know if carburizing gas used instead of heating the part in a case will produce colors.

I'm open for correction, because it will surely appear.

Tin Can.
The oxygen in the water is critical for vivid colors. You are correct in your post. The trick is keeping the charcoal packed against the steel during the quench.
Doug

I read some years ago in a gunsmithing book (a "home gunsmithing" book- the title of which I forget) where the author went through the procedure, used burned leather and bone meal, and dunped the case into the quench while air bubbled up through it. His results were a mottled grey- pretty close to what an un-colored case harden.

I mentioned all this in a post on this topic, and was corrrected that the bubbling was done prior to quenching, not during the process. That would explain the authors results. Mind you, his book wasn't about case hardening, he covered his other topics very well.

By your explanation above, I guess color hardening can't be done with carburizing gas.

Vapo-
The coloring of the color case hardening is very thin but I understood (when done correctly) the carburized hardened layer is deeper. The hardening part is critical....color-casing a gun without regard to hardening is unprofessional. When I occasionally see cracked frames of 'restored color' guns, I wonder if the hardening was mis-handled.

Even worse, there's a couple of hacks using a torch and cold blue to get almost natural colors but imagine what they're doing to the frame; tempering a section, annealing another, hardening others...These evil-doers are not case coloring - just ruination.

Turnbull and Classic Resto are good at this. They have the craft and vood00. Apparently polishing is huge part of achieving a full palette, as well as; packing material, temperature, heating/time curve, and what's going on in the water quench.

Pure water, warm, with bubbled oxygen was the late Oscar Gaddy's quench process. If you're unfamiliar with him, he's the only one who openly shared all of his work - published in series of articles the Double Gun Journal and in Q&A on the internet. He was one of the pioneers of restoring the old lost processes, and as a PhD EE he took a scientific approach to his trial and error. He also perfected the refinishing of damascus barrels, both the typical brown/white and Parker style black/white.

If Oscar were here today he would tell you in a heart beat to NOT color a rifle action like th eMauser or your Enfield or modern ones in 4140. We exchanged many emails on this very topic about 10 years ago. At the time I was in engineering graduate school and doing a lot of work with materials.

I know others do it,but that does not make it a sound enginnering decision. There will be a certain amount of failure and you are hoping that your action will hold together when setting off a 60k psi cartridge 3" in front of your face. If you are one of the unlucky ones, then you have a hand grenade going off 3" in front of your face. And all risk of this for some colors that will mostly wear off in 3 season of hard use. I used to ride bulls and would not take this risk.

Some asked on this forum a short time ago if you could color an Enfield action. My answer is the same now as it was then-you can, but you should not.

Yes , color case hardening is for color while case hardening is to diffuse carbon into the steel for strength .Color case hardening is very much an art .My Lone Star RB is done by Turnbull and it would make you drull !! I,ve also seen it done with a torch and some of the moder cheap stuff is actually painted on !! If a receive ris properly heat treated I'd leave it alone !

Here's some of Turnbull's work on a couple of my 44 Special's.