Carbonia bluing or machine bluing is one of the most beautiful finished I’ve ever seen on a gun. Found on many if not most guns made in the early 1900’s, it is one of the lost arts of the 20th century. Not many gunsmiths offer this service as there is not specific written formula that one can find to recreate this beautiful finish. I set out 2 years ago to find the formula to this secret mixture of time, temperature, bone charcoal and oil mixture that must remain in an oxygen free environment during the entire process. I built a miniature rotating furnace like what could be found in the few pictures that exists from 100 years ago. After many months of trial and error I have arrived at a finish undoubtedly like that found on the early Colt Woodsman’s that were machine blued in the vapor using the forementioned mixtures. I have concluded, right or wrong, that Winchester’s parts were more charcoal blued where Colt and Smith & Wesson (and many other manufactures) were machine blued as the temperatures and longevity of the each are different. Winchester’s bluing seems to flake over time indicating the possibility they were immersed into the charcoal where Colt parts wear off over time implying to me that a carbon reaction of the heat, smoke and lack of atmosphere brings carbon to the surface to harden similar to case coloring, which I also have done for many years but the parts never touch the charcoal. I’m excited to work on a Colt Woodsman and Colt 1902 project soon to confirm that the process works well on different era guns. I plan to do a short video to show the steps that make these restorations quite special. If all goes well, I will build a larger version that will accommodate long gun barrels so I can avoid rust bluing altogether in the future.