John and Richard - the very best cyanide color jobs can fool you; the process is very tricky to effect the "almost bone charcoal" color effect. If you recall the very earliest Perazzi guns imported by Ithaca into the US in the very early 1970s, you will remember the "zebra stripe" effect Perazzi achieved by constantly dipping and removing the receiver into a cyanide bath at the proper critical temperature. By lingering just a fraction of a second in the hot liquid, the darker violet-bluish lines would take; the short-time dip produced the much lighter, cloudy-white color. This process was an immersion-removal series process.
Cyanide colors can also be manipulated to achieve a much more even surface distribution by simply "paddling" the heated solution with the receiver; removing it briefly for examination, and reimmersing it in the bath for darker and more random color development. In this manner the receiver is kept in constant motion in the heated liquid and withdrawn periodically for inspection; when the colors "look right', it is removed and allowed to cool. So far as I know, once it is removed from the liquid bath, no more color intensification or migration takes place.
In the true classic animal-bone charcoal case coloring process as used by Parker Bros. and others, all of the components to be colored are packed into a powdered-laden crucible and fired at a prescribed temperature for a prescribed period of time. When the time has elapsed, the contents of the crucible is removed and immediately dumped into a vat of water. Years ago now, Oscar Gaddy published an exhaustive treatise on what takes place next; depth of penetration of individual component molecules in the mixture to achieve color, depth and hue of the finish, etc. In his work, he stressed that the dome of gas created when the red-hot metal parts hit the water produced rearrangement of molecules in the atomic structure of the metal, and that the secret to producing as nearly original to Parker Bros. colors was the sealing of this dome of gas over the cooling mixture as immediately and safely as possible. Loss of this gas volume, he hypothesized, was the reason for colors of diminished hue, colorations, and surface refraction.
A few years ago in Las Vegas, Doug Turnbull gave a captivating seminar on how his father Terry worked for years experimenting with the ingredients of the crucible mix to produce the Parker Bros.-like colors, and how he (Doug) continued the crusade to the method he uses today. If you want to see (IMHO) as close to Parker Bros. original bone charcoal case colors, take a look at Turnbull's standard ad where he shows the upgraded A-1 Special which began life as a VHE. They are spectacular.
Lastly, when Parker Bros. sold out to Remington and the manufacture was move to Ilion, one of the Storm brothers, who held the original ingredient formula for the colors developed at Meriden, went to Ilion to instruct the gunmakers there on how to achieve the original Parker Bros. colors. The time and precision involved in producing the colors was eventually judged by Remington to not be cost-effective, and they then went to the cyanide coloring process. As I mentioned in my earlier post, Parker Bros. actually experimented with the cyanide process themselves, but abandoned it when they could not achieve the depth, color, hue and vibrance of the bone charcoal process. The 'secret formula' for the original Parker Bros. bone charcoal case coloring process died with the Storm brothers, and many have speculated what was actually in it besides the raw animal bone powder. Theories ranged from bits of old shoe leather, plant material, rare-earth minerals, discarded brass belt buckle parts, and on and on. Whatever they put in there, the boys knew how to color a gun!
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