Frank, thanks for the reference reminder, I read the Colt info and as with many sourses, it lacks detail although interesting in mentioning charcoal, and top heat of 650 degrees. Can't find any specifics on bluing in Hamilton's book, but nice to remember my name in the index (the SAA I worked on is on pg. 160).
Does the Metals Handbook have any specifics about the carbonia process?
2152hq, are you currently offering charcoal bluing? Have you personally done the process, and are you willing to share your experiences?
Thanks much,
Steven Dodd Hughes
The 1930's era New Service was apparently blued at 650!