I teach a manufacturing process class at the University of North Dakota and I have all of my students (28 this semester) do bone and charcoal color casehardening on the baseplates for the steam engines we build. I've found during my own experiments (and that of students) that it is quite easy to get decent colors; however, we don't do gunwork at the university. Our recipe is 50/50 mix of wood to bone charcoal (purchased at Brownells) and a soak at 1350-1400 degrees for two hours in an electric furnace. I use an old 55 gallon drum for a quench tank that has been rigged up with a thermometer, airline, and a drain. We have a sheet steel lid with a hole cut out of the center. The quench process involves sliding the crucible over the hole and the air exposure is almost nil, which seems to improve the odds of getting good colors significantly. I've got really good colors at temps lower than 1300 degrees, in some cases better than I get at the higher ranges, just not as hard a surface. We always draw our parts in a 400 degree oven for 1-2 hours following the quench which I think improves the color somewhat, but it also would be a good way of preventing some sections from being to brittle.
My experiences have been the higher 1600+ temperatures don't yield great colors, Dr. Gaddy suggested many of the original makers probably stayed in the lower temp ranges. The poster that commented that this process is unsafe for firearms receivers is contradicted by millions of existing shotguns that were subjected to the same process. I'm not in the business of doing this process except in an educational sense and the only reason that I mention it is that if students with little or no prior experience can pull this process off, so can you. All it takes is a bit of equipment and a lot of experimentation, plus, it is a great deal of fun.
Last edited by Alex Johnson; 01/13/09 10:25 PM.
