doublegunshop.com - home Forums General Discussion DoubleGun BBS @ doublegunshop.com Bone charcoal for blueing?

The process described by Damascus is essentially identical to one found in an old Machinery's Handbook I have with a 1946 copyright date. They recommend putting the part in the charcoal, in an iron pot & then stirring while bringing up to heat. They also mention that sand or wood ashes can be used for a lighter color, but for the darker color pulverized charcoal should be used. No mention is made of sealing the container or that the charcoal should be bone derived, seems to indicate ordinary wood charcoal.

The American Gas Furnace process is also mentioned in this book & it does specify charred bone to be used. Also a liquid is injected during the tumbling process. What this liquid is, is not specified, probably because it was a patented process.

It is said that the liquid used in the American Gas Furnace or Carbonia process was a mixture of several oils including sperm whale oil and fish oil. It's reported that because of that, the process stunk to high heaven. It was a proprietary process that was a trade secret owned by Smith & Wesson, but Turnbull and others claim to be able to reproduce it. The Carbona process used by Colt reportedly involved heating gun parts in charcoal and rubbing the heated steel with rags soaked in fish oil. This was said to smell pretty strong too.

My tried and tested heat bluing of gun pins (screws) giving a good deep lasting blue colour is.
Firstly heat the screw to the correct bluing temperature 570F or the colour you want by eye, slowly to increase the oxide thickness. To halt the colouring process drop the screw in oil. This is where we modern folks have to substitute something for the Whale oil that gave the best colour in days gone by.
Over the years I have found three substitutes that work extremely well, though all require some heating to make them a liquid. My preferred oil is "Lard" second is "butter" the final one is "Tallow" though I do not like the smell Tallow gives off when the hot metal is dropped in.
As you can see they are all animal derived oils leaving Whales to get on with their lives.

I heat blue in Niter salts, very different from charcoal blue which is really a deep black when done correctly. My heat blue comes out more of a peacock blue.

What temp are you nitre bluing too?
Higher temps will get darker colors.

I niter blue right around 575 F. I have never been able to get a deep black with niter salts.

When I heat blue using a torch, my quenching oil of choice is olive oil. I can�t tell the difference in finished color between using olive oil or brownells quenching oil

Larry Schuknecht of Dutchman Woodworks does a nice job of blacking using niter salts. Very black, smooth finish. Even he admits though, it�s not a very durable finish. I believe a lot of early American SxS guns had their furniture finished using the niter method. .

The target temp for jet black with nitre salts is 830 degrees. But i can usually get very good color at around 750.

LeFusil, Is the heat blue durable? Enough for a trigger guard? I have one to blue. Interested as the heat blue method doesn't appear to take a lot of special ingredients!

Thanks!

It doesn't take a lot of special ingredients, but it takes a great deal of caution. Molten potassium nitrate at over 700 degrees can cause some very severe burns. Leather gloves, safety glasses, and a full face shield are good precautions. Heating a pot of previously melted salts can erupt violently as the bottom melts and the top is crusted solidly over. For this reason, put a bolt or lag screw in your pot before it cools, and unscrew it to provide a pressure relief hole when re-melting. Heat blue is not as durable as hot salts bluing or rust blue, but it is fairly durable, and a good method for screws and other small parts that won't have their temper changed adversely.