Ron's Gun Shop - Carbonia Blueing/Charcoal Bluing

What is the Carbonia finish?

One of the most common questions I get when talking to quite a few people about the restoration of their antique firearms is, "what is the correct finish for this gun"? Well, for the most part that question is easily answered. Most people know that rifle barrels and magazine tubes were all rust blued in that time period, and case coloring is easy to spot, even if there are only scant traces left in hidden areas. But what about that shiny black finish on revolvers, and rifle receivers? If your firearm was manufactured between the early part of the turn of the century and up to WWII, then most likely the blued finish is Carbonia. Which brings up the other question of, "what is that"? This is probably the most misunderstood of all the pre-war finishes we are recreating for firearms today. Hopefully some of the information I can provide for you here will be found useful or interesting in answering some of the questions that you may have about this finish (for more info on all metal finishes we offer click Here). The main area of confusion with this finish are the many terms used to describe it.

Winchester 1892 Restoration By Ron's Gun Shop

Winchester '92 Restored by Ron's Gun Shop

We have shops today which are nitre blueing, or fire blueing pieces and calling it "charcoal blueing". This is wrong. Other than nitre blueing, which is blue, blueing finishes used on firearms is closer to black. I agree with, and prefer the term the English Smiths use when describing gun blueing as "blacking". It is a way more accurate description of terms. The Carbonia process can be varied to an extent to have a little bit of a "blueish" cast to it, but a lot of that depends on the final treatment given to the steel before blueing, and in any event, the final color is still very close to black. In the Winchester 1892 pictured above, you will see three different blued finishes. The barrel is rust blued, the receiver is Carbonia blued, and the extractor is nitre blued. You can easily see which is blue and which is black. Probably the most common name that the Carbonia finish goes by today is "charcoal blueing". Technically this is incorrect. Charcoal blueing is an actual metal finishing treatment that was used by arms manufacturers, but is not the same as Carbonia. There is a difference in looks as well as huge difference in procedure for both charcoal blueing and Carbonia blueing. What ever the terms used to call it, here is a quick and condensed explanation of the Carbonia finish. Carbonia blueing, developed in the United States by the American Gas Furnace Co., is a machine blueing process, in which a gas furnace is used. The super clean parts to be blued are fixed in racks, the proper mixture of chemicals added, the parts are brought up to a specified temperature for a certain amount of time, after which they are done. The skill required of the operator to perform this procedure correctly is more of an artistic ability, rather than one of going by a predetermined set of steps to create the finish. The process I use is the authentic Carbonia method. My results are exactly that of the manufacturers of long ago, which have not produced this finish for over 60 years. It's a lot more work, and increased cost, but nothing else can come close to duplicating this finish. Besides, if your investing a fair amount for quality restoration services, why wouldn't you want to have the correct finish on your gun? The fact that charcoal is used in this process is why I believe people have improperly coined this method charcoal blueing.

Comparison of Charcoal Blue (top), and Carbonia Blue (bottom)

Here is an example of the two early Colt finishes. The top is a barrel from a 5 1/2" artillery model, which is all original Colt blue, and is an exceptional example of Colts early style blue finish. This style of finish is not Carbonia. It was in use before the Carbonia method. This finish is a heat type blueing, and yes, I do reproduce this finish as well. The bottom picture is of a SAA which is an excellent example of Colts carbonia finish, super glossy black. The above example of finish is not as glossy and deep black in appearance as carbonia, but is still a black finish none the less. Another interesting variation of this finish, which should be quite interesting to pre-war military arms collectors is the very close variant of carbonia blueing called "oil blackening".

The oil blackening process was a quicker method of obtaining the black color on the parts using a lot less time and higher temperatures, followed by a quenching process. This method of finishing provided tempering for the parts in addition to providing the final metal finish. The color was not as fine in appearance or as durable, but for it's intended purpose was more than adequate. Another military finish was using the standard carbonia method with a final bead blasted metal finish as compared to a polish, which gives the parts a nice satin non-reflective finish. Winchester collectors will commonly talk about the finish on the receivers of old rifles as having a flaky blue finish. This is a common wear pattern of this finish, mostly witnessed on Winchester rifles, and not as much on the handguns of the day.

Colt Police Positive

Another example of the finish is seen here on a Colt Police Positive. You will note the revolver does not have the mirror shine to it that the Winchester 1892 and the SAA have. This is a difference in metal preparation prior to the blueing process. Higher grade, or higher cost guns were generally given a better polish than lesser cost utility grade pieces. The finish, while not having the mirror reflective qualities, still possesses the trademark deep black color.

This picture shows the difference in shininess between the forend cap which is carbonia blued and the barrel and magazine tube which are rust blued. Well, there you have it. Carbonia ruled the day for about 50 years. It was brought to an end by the hot salt method of blueing, which is much easier, faster, and more cost effective. Not to mention the individual size of these furnaces was quite large. Colt alone had 30 of the large production furnaces, and 8 of the smaller versions for parts and special work. Talk about a hot work environment! Their gas consumption must have been unreal.

Winchester 1892 Restoration By Ron's Gun Shop

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