Does anyone here know how much control is available for the colors achieved when case hardening. I have one project I would like to have colored in golds and ambers. I have seen that some case hardened parts show only warm colors while others show only cool. But can this be taken further to exclude the pinks, magentas and violets which I do not want?

On a second project I would like blues and blacks. When I have seen case hardened work show a cool color scheme the result has always been blue and light grey with the blue fairly light. I would like my blue project to be dark, but with the splotchy and irridescent appearance of case hardening not simply gunblued. Can such a thing be done? Is this much control possible?

Thank you for the information.

Here's some info for you Brian.

Case Hardening

The following is a composite of two excellent posts on case hardening by subscribers Bruce Conner and Ward French.

It can be found at: http://members.aol.com/illinewek/faqs/case.htm

For readers wishing to pursue colour case hardening further, I strongly recommend a series of two articles by Mr. Oscar Gaddy on the subject, found in the winter 1996 and spring 1997 issues of the Double Gun Journal.

Bruce begins:

Case hardening involves putting carbon (or a combination of carbon and nitrogen) into the surface of the steel to make it a high-carbon steel which can be hardened by heat treatment, just as if it were tool steel or any other high carbon steel. Only the outer skin gets hard this way, the center is still tough and malleable. This makes for a strong part with a tough surface.

Ward continues:

Low carbon steel, i.e. steel with about 20 points or less of carbon, cannot be made to harden by heating and quenching, as higher carbon steels can. Low carbon steels are tough, soft and flexible. They wear quickly and batter easily.

Many parts, including gun actions in days gone by, were made with low carbon steel. It was cheap, strong and easy to machine. Unfortunately it would not stand up to the battering of use in the field. Case hardening added carbon to the surface skin of the steel part and left it in a state which could be hardened by quenching.

To case harden a part (the process is also known as pack hardening) the finished low carbon steel part is placed in a sealed container, packed with a high carbon compound. In the old days this was simply animal hide or bone. The container filled with parts and carbon bearing material was brought to a red heat and held at that temperature for a time determined by the size of the part. The time might be from a half hour up to several hours. As the bone or hide became carbon in the container, and a carbon rich gas formed, some of the carbon would infuse into the surface of the steel. Over time this would penetrate several thousandths of an inch, producing a high carbon surface on the low carbon steel part.

At the proper time the container is removed from the furnace and the contents dumped into a quenching bath, usually water with perhaps a surface coat of oil to lessen the shock of the quench. The high carbon surface skin becomes glass hard, but the low carbon body of the piece remains soft and very ductile and able to resist shock. Properly done it made a simple and very durable system for treating metal action parts.

Colors are produced when the steel surface is cooled unevenly, capturing the natural blues, oranges and yellows of cooling steel. Several methods are employed to do this. Stevens moved the parts into the quench in a jerky fashion, producing a barred effect of color. Perazzi did the same. In the London trade the quench bath, usually a barrel with soft water and a skim of oil, was agitated by stirring, or with bubbles of air, producing a mottled effect on the steel.

Bruce adds:

Color case hardening is done much the same way except that generally only leather and bone are used as the carbon source. I don't know why this works better than charcoal, but it does. You get more brilliant colors with them. The other thing you do is modify the quenching bath. You need a source of bubbles. LOTS of bubbles to really rile up the quench bath. Adding a bit of potassium nitrate to the water increases the brilliance of the colors as well, but isn't a requirement. You have to watch the temperature more closely with color case hardening or the colors won't come out well. Don't go over 1350 F.

Kasenit and similar compounds are a lot easier to use and you can just use a torch. You heat the part up red, dunk it into the Kasenit compound and get a good coating of it sticking to the steel in the places you want hardened. Then reheat it up to a good red and quench it in water. This can be repeated to increase the depth of the case hardening. It works very well and is quite fast, but leaves a kind of dull grey color to the surface. For parts that are internal it works great and if you make the hardening deep enough, you can polish the metal and still have a hard surface.

Ward continues:

The colors have nothing to do with the effectiveness of the case hardening. Many, if not most, parts are hardened without colors. The surface takes on a dull gray look. The London makers usually polish this surface bright. It is glass hard, but without the decorative affect of the colors.

Anyone who has a case colored part should be aware that colors will fade on exposure to direct sunlight over an extended time period. Parts must be protected. Clear fingernail polish or a similar lacquer will protect the surface and a gun case or cabinet will do the rest. Case hardening was widely used on all lock parts except springs, and the process could be carried out even on the frontier with a minimum of equipment and knowledge.

Here’s some outfits that do color case hardening.

http://www.z-hat.com/color_case.htm
http://www.lonestarrifle.com/casecolr.htm It has a pix of their work.
http://housersgunsmithing.com/gunsmithservices1.html
http://www.danthegunman.com/
http://www.runniron.com/finishes/color_case.html

Here’s a complete color case hardening kit from Brownell’s

http://www.brownells.com/aspx/ns/store/productdetail.aspx?p=1026

In the winter 1996 and spring 1997 issues of the Double Gun Journal, color case hardening is explained in detail, these issues are available from the publisher at P.O. Box 550, East Jordan, Michigan 49727.


Here’s some video tapes that may help you.
American Custom Gunmakers Guild
Publications/Videos
ACGG offers various publications and videotapes for purchase. Most orders can be shipped via USPS Priority Mail within two weeks of receiving the order. Prices include postage, except for non-United States destinations. We do not accept on-line orders, but you can print out an order form to mail or fax. (PDF files are require Adobe Reader available free from www.adobe.com.)
Here’s the link.
http://www.acgg.com/pub.html
1997 - Tape 1
Color Case Hardening by Mr. John Hackley
• Mr. Hackley shared his experience, tricks, puzzles, and frustrations. Includes 24-minutes in shop experience as well as the seminar presentation. Additional feature includes Pete Mazur in his shop demonstrating Nitre blue.


That should keep you busy for a while.

I have wanted to have some stock hardware etc. case hardened and in my researching I believe this is what causes the coloring and any patterning- the carbon source and the quenching method. I think every gunsmith that case-hardens uses a different carbon source in their case hardening... some use bone charcoal, some charred leather, others hooves etc. and I think that makes some difference in the result. The patterns I believe come from how violent the quenching is, as far as different substances that are used to quench or different ways to disturb the quench (bubbles?).

I hope my limited knowledge helps some. I have wanted to experiment some with case hardening, and if my principal at school (high school) wasn't such an idiot (doesn't understand that buttplates or grip caps are not critical parts) the shop teacher would have gladly helped me.

About a month ago I asked this question of one of the Case Hardening houses. But they apparently did not feel any need to answer email.
I may try another metal treatment house soon.

Call them. Easy for email to get lost in a spam filter.

Brian, contact these folks. They are well versed in color case hardening and can consistantly offer differing color combinations. The 1930 FN action I had them do came out in wonderful shades of browns and straw with bits of blue hue included.

My brother does the case hardening for a fairly well known gun company. I doubt he knows the difference between "warm" and "cool" colors much less exactly what color magenta is. I know I don't.