This has probably been covered before, so please forgive me in advance.
I recently purchased a "new" Model 21 with a beautiful case colored finish on the frame. I realize that true case coloring fades over time, but from what I have researched, this was a chemical vs. heat application . It appears to have a clear coat or laquer finish. In any case, it has almost disappeared in places. How can I preserve what's left of the finish, if at all, and if I can't, does anybody still do case coloring the right way? Any help would be greatly appreciated.

Thanks!

Doug Turnbull is the name most often mentioned when it comes to case coloring although there are other firms doing this work. There is a commercial heat treating firm by the name of Fred Heinzelman that used to do firearm case coloring. I visited them years ago in the 1970's, they were doing Griffin & Howe's case coloring so you know their work is first class. A Google search will produce the names of other firms less well known than Turnbull. Turnbull's work may seem pricey but he has decades of experience and your job will get done right with no disappointments. I once owned a Winchester 1886 that Turnbull had case colored, it was a beautiful job of restoration. You are correct in your finding that many of the guns of recent production have colors that are chemically produced. They are even more fragile than real case coloring, I have no idea how to preserve them.

Thank you, sir! I will take a look at the gentlemen that you recommended. Otherwise, I guess I'll just have it blued.

I have several old single shot rifles with case hardened receivers. The case coloring is fragile especially when exposed to light. The blued finishes stand up to a lot more punishment.

I think Turnbull did the Classic series S&W casecolored frames. Don't know if he's still doing any work for them.

Keep a protective coating on the colors. That's the best way to preserve the look. We used to use orange shellace on the restoration jobs as that's what the most of the original makers used. Laquer, even a thin coating of tru-oil works well.
But the colors are fragile. They are after all just a by product of what was the real purpose of the process--to harden the surface of low carbon iron & steel.

Heintzlemann uses cyanide process for color hardening. They've been around since WW1 and were the company AH Fox sent their shotguns to for color hardening starting after WW1. That's when they changed from bone/charcoal casecoloring (same type that Turnbull does) to the Cyanide process.

I used to send an occasional Fox restoration to Heinzelmann for coloring but haven't since the late 90's.
Parkers also started being cyanide colored when Remington bought them out and moved the operation to Illion NY. Before that in Meriden CT,,they too were bone/charcoal hardened.

Cyanide colors have a different look to them. They tend to be a bit tougher and resist wear better than bone charcoal.
You see cyanide colors on Stevens, Iver Johnson guns too. A wavy rainbow look to the sides of the receivers. That's a result of a staggered quench opperation.

Cyanide case colors will be hard surfaced. Bone charcoal colors may be either hardened or done w/o hardening the surface,,just giving the customer the pretty colors they want w/o hardening the metal at all or very little.

The best way to preserve them in 100% condition is make the gun a safe queen. Other than that they will wear and wear fairly fast.
Some like the look of a it when they start to wear, especially on an engraved piece where the light and dark contrast of the color in the cuts makes for a particularly stunning effect.

There area couple of ways to enhance existing case colors but I hesitate to mention them. You can easily do more damage than good and alot depends on wether the surface was actually hardened or not when it was CCH in the first place. Many are not.