Well said Edgar.

I take issue however, with your statement that "the colors achieved in the process are a secondary byproduct." If that were the case, Parker, as well as virtually all other gun manufacturers, would not have refined and guarded the formula of the types and ratios of organic material that the receiver and other parts included in the crucible were packed in in order to achieve the colors that are usually definitive to a particular manufacturer.
In my opinion the colors produced in the case hardening process became as intentional as the case hardening itself.

This is not to detract from your very learned description of the hardening process, but only meant to shed light on the intended resultant colors.

Your pal, Dean





.

On the DH yes. The late great Russ Bickel did them.





.

I wouldn't expect anything else from you.

As an engineer by profession, It is my view that the case hardening process is a heat treat process, not an esthetic procedure. It is part of the process of a manufacturer, so that function and durability are incorporated in the final product. This is the Primary purpose, and proof of the process is by testing the surface hardness of the product, by achieving some measureable result. Today, that would be by Brinell, or, more appropriately, Rockwell testing. This test is specific.
Aesthetic, eye appealing colors are subjective and might vary from one person to another, but certainly it was known that the colors were appealing, and procedures to closely reproduce those colors from piece to piece were important. The idea that the process was a 'closely guarded secret' is intriguing, and even legend, but other than Colt Patent Firearms, I never read anything elsewhere stating it was so. We just want to believe that. Was it true? Maybe. However one only needs to look at other makers to know they too knew how to do it. Charles and Walter wanted first to be sure the gun was sufficiently heat treated to withstand use, and second to see that it was eye pleasing.

Okay, I'll go along with the color being a by-product of case hardening and even "secondary" when viewed in that context. But I didn't say the process was closely guarded, but that the "formula and ratio of organic material packed into the crucible with the parts" was closely guarded by each manufacturer.

Good discussion Edgar and I bow to your expertise.





.

Thank you gentlemen for answering my question so thoroughly.
What a great resource this forum is for these fine guns.

Beautiful gun Dean

The DH is mine but the AAHE 16 belongs to a friend.





.