Color variations in color case hardening

partsproduction · Dec 4, 2020

I've seen a few CCH guns and the colors that look best to my eyes are bright blues with red highlights. Of course this is something I'd like to do. One video of CC Hardening had the fellow mentioning that he likes a specific ratio of wood charcoal to bone and hide charcoal to get the colors he likes, and that got me wondering if there are any chemical salts that can be added to the packing to make more fire color?
Thanks,
parts

john.k · Dec 4, 2020

Simple-cyanide.....or more specifically cyanides of alkali metals.....Do wash your hands after use tho.

FredC · Dec 4, 2020

Never done it so I am not 100% certain but I think another part of getting attractive colors may be quenching in water that has a bubbler in it.

NRDock · Dec 4, 2020

It doesn't look to bad to try, but I fear that unless one wants to keep at it long enough to become an expert, it's probably better to just pay an expert.

One thing I've noticed with my CCH guns is that these areas rust easier than blued steel. A few years ago I had to store some guns in marginal conditions. When I spot checked the blued ones they looked fine. Upon returning the guns to proper storage, I discovered various degrees of rust on the CCH. The finish on my CCH custom shop Contender frame was effectively destroyed.

Paolo_MD · Dec 5, 2020

I believe that the color are given by nitrogen salts (present mostly in bone and hide charcoal). And, yes, I think bubbling is essential both for the color development and for the shape of the pattern (i.e. less bubbling and agitation, larger and more uniform patches).

Paolo

partsproduction · Dec 7, 2020

Thanks, experimentation makes sense, as one guy mentioned a secret formulae based on proportions of bone/leather charcoal and wood charcoal. His colors were very bright BTW with lots of reds and oranges.

steve-l · Dec 7, 2020

I have not done this for awhile, but I remember the actual color of the result was a product of the steel alloy, ie hardness and/or the the temperature of the salt bath. Where the salt bath temperature is controlled by changing the boiling point by adding either salt or water to the mixture.

Paolo_MD · Dec 9, 2020

steve-l said:
I have not done this for awhile, but I remember the actual color of the result was a product of the steel alloy, ie hardness and/or the the temperature of the salt bath. Where the salt bath temperature is controlled by changing the boiling point by adding either salt or water to the mixture.

Are you talking of hot bluing, or case-hardening?

Paolo

steve-l · Dec 10, 2020

Paolo_MD said:
Are you talking of hot bluing, or case-hardening?

Paolo

Hot bluing. It is not uncommon that parts of the gun are not always of the same alloy or the same hardness. If hot blued together, you will end up with different colors.

Paolo_MD · Dec 10, 2020

steve-l said:
Hot bluing. It is not uncommon that parts of the gun are not always of the same alloy or the same hardness. If hot blued together, you will end up with different colors.

In this thread we are talking about case hardening which is a completely different process in which you add carbon on the surface layer of low-carbon steel (i.e. hardening it through the quenching step). If the packing contains other minerals (generally present in bone and hide charcoals) and the quenching brings oxygen to the cooling surface, the result is the formation of various superficial (and very hard) oxides giving patches of different colors on the same, uniform piece of steel.

Paolo

steve-l · Dec 10, 2020

Paolo_MD said:
In this thread we are talking about case hardening which is a completely different process in which you add carbon on the surface layer of low-carbon steel (i.e. hardening it through the quenching step). If the packing contains other minerals (generally present in bone and hide charcoals) and the quenching brings oxygen to the cooling surface, the result is the formation of various superficial (and very hard) oxides giving patches of different colors on the same, uniform piece of steel.

Paolo

I don't think the issue is different. It is the same. Hardened steel is more difficult to color. It makes no difference what method you use to create the oxidation layer, it takes not only longer in salt exposure time and concentration level in use. As the oxidation layer builds the color of it also changes. When the color of the surface is light the effective corrosion protection is also light, which is the subject of this thread. CCH is not very effective at creating corrosion resistance in any case. If a color change and corrosion protection is desired, it must be done by a different process AFTER case hardening.

pat_j0nes · Dec 10, 2020

steve-l said:
I don't think the issue is different. It is the same. Hardened steel is more difficult to color. It makes no difference what method you use to create the oxidation layer, it takes not only longer in salt exposure time and concentration level in use. As the oxidation layer builds the color of it also changes. When the color of the surface is light the effective corrosion protection is also light, which is the subject of this thread. CCH is not very effective at creating corrosion resistance in any case. If a color change and corrosion protection is desired, it must be done by a different process AFTER case hardening.

I don't believe you understand the process they've been taking about. Case hardening is a hardening process. When done with traditional bone charcoals, it just happens to leave pretty colors. When you heat the metal to critical temperature (red hot) in the furnace, it aneals the steel completely.

You may be thinking of some of the other processes that mimic these colors.

--
Pat Jones
Firestone CO

john.k · Dec 11, 2020

A lot of confusion is caused by the by the restorers who use "sub critical case colouring" in restorations.....pretty colours ,but insted of hardening,these processes actually soften the end result....New guns may also have the subcritical colours ,as the material used is 4140 ,and is not adversely affected by the heat involved.

1yesca · Dec 13, 2020

just think about what is happening to the part being cc its like kicking someone off a roof and then going over and asking them are you ok

72bwhite · Dec 17, 2020

a lot depends on if it's an antique or a modern gun
the color on the old stuff was actually just a by product of the
case hardening process used.
the modern reproductions it's kind of like cold blueing process.

remember in the old days it was just plain old low carbon steel
if you wanted it harder you packed it in charcoal cooked it and quenched it.
for real honest color case hardening some mixture of bone maybe some leather and wood charcoal is
used. and some times it gives good colors and some times not.

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Color variations in color case hardening

partsproduction

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john.k

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FredC

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NRDock

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Paolo_MD

Stainless

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