Nitre Blue Colt 1902

by Clint Hawkins
Hawkins LLC, Pro Course Graduate & GCA Charter Member

The Tragedies and Triumphs of a Gunsmith

“Best foot forward,” they always say, but you have to know the story! This is not a story about how great I am in doing Nitre Blue for you will quickly see that’s not true, or even how great the results can be if you use it on your projects. It is really about the things you need to watch out for to successfully complete the project. Gene Shuey shows all the right things to do and how to do them in his Rust and Nitre Bluing course. AGI courses do warn about what can happen “if” … but their time is too valuable to show anything except what is the right result.

Photo 1--the original

Photo 1–the original

This gun came to me looking pretty bad. Rust pitted, worn, beat up, actually. My client wanted me to restore it to as new as possible. It wasn’t possible to make it “like new” for a number of reasons, which we will go into, but it was possible to make something that looked worse than this Google photo (1) into this shown in photo 2. Actually, my client wanted it to be a little bit customized. He wanted it to be as close as possible to original color for the frame and slide, but he wanted a Peacock Blue for the screws and pins. The hammer and lanyard ring swivel was to be Color Case Hardened. That was the easiest part. He, being somewhat of a craftsman himself, was going to make custom hardwood grips for it.

Photo 2--the goal

Photo 2–the goal

The first problem was the frame and slide, as they were in terrible condition. The only way to get rid of the rust pits and dings on the sides was to have them surface ground by my trusty machine shop (everyone needs one of those). Further examination also showed that someone else had worked on this gun, as evidenced by the rather plain Bakelite grips and for some odd reason, the extractor pin hole at the top of the slide had been welded over. This needed to be drilled out. The extractor itself was broken. The weld had also been poorly done, leaving some pits and small sink areas in the top of the slide. To restore the contour, those areas needed to be filled in as well. The problem was the steel was porous enough that bubbles kept popping up until it was obvious that further effort would be non-productive.

After the surface grinding and re-contouring was completed, the only stamping that was left was the serial number, which indicated this gun was produced in 1914.

Other than to make you aware, for the purpose of this article, it is not necessary to mention the tremendous delay that can occur when using out-of-shop services.

It was my plan to provide all the colors wanted by my client using the Nitre Blue Process. Gene Shuey gave excellent instruction in his course. If you pay close attention to that course, you will notice that all the parts he puts through the process are small. This is for good reason. Large parts are more difficult to process because of uneven mass concentrations. You will notice on the Mauser extractor, that because of the varying thickness the colors did not come out even until sufficient time brought the mass of the extractor to the same temperature.

In consulting with Gene, he advised me that while it was possible, but not advisable, to use Nitre Blue, I might get better results if I sent the gun to Turnbull Manufacturing in New York. Turnbull informed me that they used the same Charcoal Bluing method used by Colt from the late 1890s to the late 1920s for their restoration work. I told them about the removal of the Colt imprints, and they informed me they also had the roll stamps that would give the same imprints the gun had been manufactured with. Eureka!! I so informed my client and he said, “Do it!”

A few weeks later, Turnbull informed me there was a problem and that they were just going to send it back. The primary issue was the welds introduced different steel alloys that would not produce the same color as the main steel alloy. And, with their very apparent bubbles, it would give results with which Turnbull did not want their name associated. The only thing that took some of the sting out of that was that without the welds, the slide would still have the dings that Turnbull still would not put their name on.


On the other hand, that also meant that I was back on the other, difficult, plan of nitre bluing large parts. I reasoned that since the primary cause of concern was the stabilization of temperature of large variable mass concentrations, I could eliminate that concern by immersing the large parts as soon as the salts became liquid and bring the temperature of the metal up with the salts, instead of immersing after the salts were up to temperature, as is often done with small parts.

This strategy proved to be correct. I had little difficulty in that regard. Now, however, I will reveal the real challenges experienced in what should have been a rather straightforward job.


I was really only interested in two temperatures: 570° for Full Blue and 640° for Light Blue. Here was where a considerable number of variances came into play, temperature and alloy, not to mention the possibility of calibration of the gauge. The plan was that when the frame and slide reached their temperature of 570°, they would come out and the small parts would go in and they would have their masses equalized by the time 640° was reached. That was the plan.

Reality is often different than plans. As General Eisenhower stated, “Plans are useless; planning is essential.” The alloys of the frame and the slide just happened to be a little differ-ent, would they be ready at 570°? The frame wasn’t ready to come out of the bath until 580° and the slide at 590°. Not a real problem. Then, in go the small parts in a Stainless Steel Tea Ball with the trigger hanging on the handle. On we go to 640°. No Light Blue. Well, the parts obviously needed more heat, so we’ll just keep going up. My 15,000 BTU burner topped out at 690°. The small parts were just as dark as ever.

Folks, the pictures I am showing here are the results of not one, not two, but seven different firings. I thought that somehow the alloys in the small parts were different and maybe needed a lower temperature, and I had just skipped right past it. So, I polished the parts again and started over, going very slowly after going yellow and checking about every 10°. Nope. I went all the way back up to 690° without seeing Light Blue.

Next, I contacted Brownells. They assured me there might be a very small likelihood of the gauge being off, but, more likely, the alloys involved here just never would turn Light Blue. They told me that they had given a demonstration of Nitre Bluing and had gotten some results that were quite unexpected.

A number of other attempts were made to get that blue. The last such, I even applied my handheld propane torch to get even more heat. At 740°, I called my client and asked if he would consider the idea of a golden yellow color. As we talked, the temperature topped out at 750°. It just not would go any higher. I pulled out the parts and the trigger showed (GASP) a Turquoise Blue. This was achieved at a full 110° off the top of the color chart! Of the small parts in the Tea Ball, only the Take Down Plug and Slide Lock took on that color.

The Magazine Follower came close. Everything else was still a pretty dark blue with just a hint of the lighter color.

Now comes the tale about the last two firings. As I started to put the pistol together, I noticed a rash of tiny white spots on the slide near the front sight. “Aargh,” I thought, “how could I be so stupid as to get that next to something that would mar the finish?” Upon looking around, I could see no such thing that would account for it. Air Bubbles!! Gene had taught us about air bubbles, and he had avoided them by swishing the parts around in the salts bath. I had not been able to swish vigorously enough with the large parts and did not get rid of the bubbles. Brownells had suggested using 000 steel wool to scrub air bubble off the parts.

Another firing would take care of that. Repolish and reimmerse in the bath using a cut off pad of steel wool held by a set of mechanical fingers. By gosh, I got those bubbles this time. “YIKES!! What happened? I do better clean up work than this!?!”Nitre3

The slide at first looked like it had gotten caught in a sand pit. Thorough cleaning showed nothing wrong with the surface, although it needed to be polished again. What caused this? Aha! In my haste, I had not cleaned the steel wool. The salts didn’t want the oil but the steel did. Steel wool looks clean, but isn’t. Cutting off a fourth of a pad and rinsing it in about a pint of lacquer thinner gave a pretty brown result. Another rinse in fresh thinner gave clear and we’re good to go.

Time & Money

Nowhere in the course or in Brownells literature is there any mention of the time involved. My client is fortunate that I cannot charge him for all the time I have spent on this project. I use a Flat Rate Sheet that I made that uses data from two sources. Each publication of Brownells main catalog has a Shop Price Survey which is a cross-section of their Gunsmith/Dealer customers across the country and we, as students of AGI are privileged to have the gunsmithing worlds only Flat Rate Time Manual. My Flat Rate Sheet then reflects my determination to anchor myself very close to the mid-range of the gunsmiths across the country. This is to remain competitive without undercharging myself out of business.

However, in the case of this particular gun, while I feel that I cannot ethically charge more than the original quote, except for the unanticipated additional work that the client is informed of and authorizes, a great deal more time was involved due to the nature of the alloys, and the time required heating the solution. Using the diffuser plate nearly doubled the time. Without it, the time required in my set-up was about 1-3/4 hours to reach the 570° temperature that the chart said would be correct for the frame and slide. It took about another 10 minutes before they were actually ready for removal. The small parts, required almost another 45 minutes to come up to the final temperature, which you may recall was 110° more than indicated by the chart.

Cool down time is about 1-1/2 times the heating time. During the entire heating/cooling cycle, one must remain with the set-up for safety and liability reasons, if other people might be able to come in contact with it. Total time for a normal bluing process should be just over 4 hours.

Nitre4None of the previously mentioned times include the time involved in experimenting to find the correct temperature for these particular small parts. Altogether, not including the two firings to correct my mistakes, I spent over 20 hours. At $65 per hour, that’s a bunch that I could have been making on someone else’s guns.

Finally, here is something that will make my client happy. There is an iridescent beauty in it. He’s waited long enough for it.Nitre5

Tank Set-Up

Gene shows a stainless steel bowl in his course. In many ways, this is superior to what I used and Gene tells why. In my mind, there are two reasons: 1st is that, being round, there is more efficient transfer of heat to the salts, and 2nd, more visible change in color without removing the parts from the bath until it is time to be more critical in the observation of the color. My application requires portability that is more difficult to achieve with a bowl. So, I used the iron quarter tank recommended by Brownells. Be aware that a quarter tank, while more amenable to the shape of pistol frames than a bowl, still leaves very little room for a large pistol.

Even that would not give me the portability and safety that I required. I needed to be able to safely move the tank out of the way quickly, and also to store it with the salts in it. It seemed to me that handles and a lid were a necessity. Those additions to the tank cost twice what the tank itself did, but I now have a dedicated nitre bluing tank that I fully intend to put to use.

Nitre9The other photos show my barbeque grill with two 15,000 burners (minimum requirement), stainless stirring spoon, and steel wool with mechanical fingers for removing air bubbles, using the lid as a trivet. Also shown is the iron diffuser plate recommended by Brownells to help eliminate hot spots.

I found that the diffuser plate greatly slows and limits the heating of the salts. Stirring is much more efficient in solving hot spot problems, especially when you start getting within 30° of your target temperature.

The amount of salts is also important. Those of you who are acquainted with me know that I am a cheapskate. I started out with 10lbs. of salts. You really need 20lbs. Save ordering the 10lb. buckets for replenishing the loss from drag-out. The Haz-Mat charges are the same. Every time you pull parts away from the tank, you lose some of it. I was astonished at how quickly the level went down.

Jump in, the water’s fine.

Avoid the salts, though, they’ll burn ya.

3 Responses to Nitre Blue Colt 1902

  1. Oh what a pain bluing as such looks like. Glad others do it though.

    Really good article and well written Clint, thanks a bunch for sharing! Cheers

  2. Great article. I do this for a living, so it’s nice to see info that includes the time sensitive thoughts, as time equals money! A good source for stainless steel containers is a restaurant supply house. They usually have a good selection of used stuff and at reasonable prices. I’m with you on diffuser plates, they really slow things down.

  3. I have a question. Even though it would be an additional piece of equipment, why not use a heat oven/furnace to pre-heat? Even a toaster oven type that reloaders are using for the powder coat craze? That go to about 450.

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