Re: Case Color Hardening

[Roger Stanford]

I've been case color hardening for a few months now with consistant results, I use the standard 4/1 bone/wood charcoal mix, 1400 degrees for from 1 hr 15 min to 2 hrs. Aerated quench water from 50 to 70 degrees with no air gap. The colors are good with grey edges. concistant with modern CCH shops. I am trying to duplicate the older colors of the Stevens and LC Smith with no grey edges. Any suggestions ?

 

[Swede]

You've obviously researched CCH. Did those guns you mention use cyanide? I was always under the impression that the traditional charcoal CCH was more grey in color, and to get the outrageous blues and magentas calls for molten cyanide.

Have you tried adding anything to the quench? I've heard of heavy concentrations of potassium nitrate in the water, an oil slick on the surface, combination of both.

 

[Roger Stanford]

I've read something about cyanide in the process and you are proably correct. That seems to be something dangerous they would have used in the old days {before OSHA} I had'nt heard of the oil slick. Something I'll have to investigate. I've also read about the sodium nitrate in the quench. but I have no idea what the concentration would be. So many secrets of the art died with the old timers.I've never read any definate instructions on the process. Everything so far has been " You just have to experiment" There are a few commercial shops that case color but rightfully so, they guard thier secrets.
Thanks for the response and ideas.
Roger

 

[bezalel2000]

Hi Roger

Just curious, are your temperatures measured in F, C or K ? :-\

Bez

 

[Roger Stanford]

Farenheit. One hard lesson I learned about temp. Use two pyrometers, preferrably digital. Had the "one" malfunction once and overheated a piece by at least 400 degrees. Part hardened so much it became too brittle. Repeated annealing did'nt even work

 

[Swede]

Long ago, I had a chemistry background, and there is something to potassium nitrate as a coloring agent. Potassium nitrate salts melt fairly low temp, and immersing carbon steel in them will give them a rich blue. I think what might happen in a quench heavy with KNO3 is that the water flashes on the steel, leaving behind the KNO3, which has moments to deliver its color before washing away.

If you want to try it, you can buy KNO3 at hardware stores where it is sold as "stump remover", maybe $4 for a pound. I'd dissolve as much as the water can hold. If it works well, it can be purchased in bulk for less than $1 per pound.

Yes they did use cyanide salts, and I think they still do industrially. Definitely avoid it, sooo dangerous. Good luck, let us know if it works. Personally, I love the more subtle CCH that bone delivers.

 

[Roger Stanford]

Swede
Thanks for the information on the sodium nitrate. I'll give it a try next time I color and will let you know the results.

 

[Swede]

Roger, look for potassium, not sodium, nitrate. Makes a difference. Good luck w/it.

 

[flatbelter]

Other thing is the color depends on the oxide thickness, try getting it from the oven to the quench faster. One old reference I had used a closed container to hold parts packed in the carbon source. They just opened the lid and dumped everything into the quench. It did mention the need to watch out for flying sparks and such. I haven't tried it that way myself.

IIRC nitrate (with sodium hydroxide) salts in water are used for hot bluing steel for firearms. Molten nitrates can be used as a high temp heat treating media and wikipedia says that they can also be used for coloring refered to as niter bluing.

Cyanide just made the process faster (deeper hardening) IIRC.

 

[Roger Stanford]

My elapsed time from the oven to the quench might be 30 seconds. I position the delidded crucible over the water, open end up. With a quick twist of the wrist, I'm able to dump the charcoal and parts with nearly no air gap. And I HAVE experienced the charcoal shower once. That's all it took to learn to wear sleeves.
Thanks for the response
Roger

 

[maverick]

My experience with CCH was rather brief, one week at a NRA sponsered summer class. It was a two man operation

to quench the parts. One man latched the handle onto the crucible and removed it from the oven, then set it on

the ground where the second man popped off the lid. Then the first raised up the crucible, turned it over and

slammed the handle down on the edge of the quench barrel to eject the parts. The less time hot parts are exposed

to air the better. We used an 80:20 mix of wood to bone charcoal and an aereated fresh water quench. The

instructor told us that spraying 409 cleaner on the parts before packing would enhance the colors. I did see some

very nice colors on our parts.

 

[Swede]

I used to use ceramic pots (modified flower pots) for CCH, and you can turn the quench into an easy one-man job by resting the tongs on the rim of the quench bucket and simply popping the pot with a hammer. Everything gets dumped instantly into the quench tank. A screen is in the quench to collect both the parts and anything else that might sink. It's messy but effective.

 

[Roger Stanford]

409 cleaner huh ? wonder what's in there that would make a difference. It's worth a try. I've always heard that there is a certain amount of witch craft in CCH.
Again, thanks for the replies
Roger

 

[44-henry]

Roger,
I have been doing this for several years in my university laboratory. I have posted quite extensively on the process that I have used both here and on other forums. It sounds like from your description that your temperature and bone to wood ratios are reasonable, as is your quench temperature, and soak time. If you are keeping your gap between the pot and the water at zero you can't get much better than that.

That still leaves a lot of things that you can try. I never found the air lines in the water to be all that critical; however, I do believe that oxygen concentration in the water is critical. I tend to wrap parts with soft iron wire prior to placing them in the pack and I think this has more effect than the air stream. I also pay a lot of attention as to how I place parts in the pack, and the blocking that is used. This provides much more control than just random placement. I also use chemically pure charcoal purchased from Brownells and other sources.

I do use nitrate in the water occasionally, but if you use too much you will find your parts are almost completely blue. I do think that some of the original recipes contained potassium cyanide (Howe even mentions its use in his book), but as too how much effect it had I do not know. If you are to believe Howe (and I really have no reason not to) it supposedly made colors appear rather gaudy. I briefly thought about using the stuff once, but the dangers associated with using it and disposing of it outweighed the potential gains. Besides, I get very good colors without it so I really don't know what the point would be. If you are really curious than try making charcoal out of things like fruit pits and try those, many contain trace amounts of cyanide and would probably give some indication of the effects that could be achieved. I have used less dangerous cyanide's with no noticeable differences in dozens of tests, not to mention a host of other chemicals.

I have a new Johnson Triple Treat furnace with digital controllers that arrived a couple days ago. When I get it set up I plan on doing more experiments during the coming semester, I will post back if you are interested.

Regards,

Alex Johnson

 

[Swede]

Great information, Alex, thanks. CCH is a tad voodoo and it can be pretty frustrating to have a complex part ruined with a failed attempt.

The "other" cyanides are materials like Kasenit and similar, which use a ferrocyanide molecule like potassium ferrocyanide. While not totally safe, it is 1,000 times better than the straight cyanide like potassium cyanide. I've actually made homemade Kasenit using ferrocyanide, which is cheap and can be bought as a photo chemical, but of course there are no colors.

The old cyanide true CCH was, I believe, a bath of pure molten salts of KCN. One spatter in your mouth or eye, and you are dead. One drop of acid into the KCN and you get a gas, hydrogen cyanide, that'll drop you in your tracks. The old California gas chambers used to use KCN pellets dumped remotely into an acid bath to do the job.

Enough said on cyanide!