Steve,
I believe the bone smoke and sperm oil is a simple charcoal bluing process (Winchester called it “Machine Bluing”). Ned Schwing wrote about it in his Model 21 book on page 43/44 as did Renneberg in his Model 94 book. Both authors reference the sperm oil and bone smoke. Pauline Muerrle also has an employee reference for Winchester using this process with sperm oil in her book “Winchester, The Way it Really Was”. Pine tar was one of the eventual substitutions for the sperm oil.
Doug Turnbull does it. http://www.turnbullmfg.com/ The process uses some of the same equipment and material as case-hardening so I am sure there are other restoration specialists that can still do it also. Do a search for “Charcoal Bluing”.
Hope that helps.
Regards,
WACA Life Member #6284 - Specializing in Pre-64 Winchester .22 Rimfire
JWA,
I first heard about it from Ned Schwing in his Winchester Slide Action Rifle books. They did in fact refer to it as “Machine Bluing” The process sounded very interesting to me. Ya just have to have an oven big enough to hold the parts that will heat up to 850* for a long period of time. Pretty cool how they must have figured that out.
Steve
I believe the gas fired ovens also had a rotating retort which is not typically found in most small shops. It seems to be a very simple process using a bone and oil formula which most manufacturer’s kept proprietary, the oven is the key though.
Best Regards,
WACA Life Member #6284 - Specializing in Pre-64 Winchester .22 Rimfire
Winchester bluing. Always an interesting subject. Pick an era of your choice and you might likely find guns that are a very dark, black like blue, and those that take on a much lighter shade…the difference being like night and day. Trying to figure out the why of it all is fun, huh?!
I really liked reading Mike Hunter’s article Winchester Metal Finishes, 2014 Fall Issue of The Winchester Collector Magazine.
James
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