St. Ledger and other English firms reportedly used human bones at some point, imported from India. Bison bones reportedly were used in America during the latter part of the 19th Century. As were other carbon and phosphorus sources. It all really comes down to chemistry and methodology.
Again, methodology varies, as not too long ago I had a discussion with the teacher of a gunsmith school who was convinced of the need to quench at above critical temperatures, in direct contrast to Gaddy's technique, the points being covered in Gaddy's letter to Frank Brownell that I posted not too long ago. I tend to agree with Gaddy, as the actual science was not known at the time, as well as the ability to tightly regulate forge temps. Techniques were developed by trial and error, with the result being the pack to cool to below critical temp for the quench, eliminating distortion, brittle metal, and the need for "hard fitting".
It looks to me that DT changed something in the recent past, resulting in better color coverage, but with some changes in resulting colors.
Last edited by Ken61; 11/03/16 12:35 PM.
