Pig Hunter
Member
Does anyone have a clue at what temperature range the old bluing process was used ? I have tried a similar system, but at a temp that would alter the heat treat on frames or cylinders. Experimentation continues.
Carbona bluing
- Thread starter Pig Hunter
- Start date
Register to hide this ad
DWalt
Member
Precise information is very lacking on exactly how the Carbonia process was performed.
cgt4570
Member
Copied from a 'firing line' thread from 2002:
Haven and Belden "A History of the Colt Revolver" reprints "A Century of Achievement"
"Frames, cylinders, barrels, slides, receivers and parts come to the bluing room direct from the polishing department. Side plates and cranes are removed. Everything is first given a bath in hot gasoline… gasoline heated to 150 deg F. This removes all dirt particles, dust, or grease that may have gathered on the way down from the polishing room. Hot air is then forced over them to eliminate all presence of moisture – the arch enemy.
After washing and drying is completed, the side plates (revolvers) are put back on. But they are put on with work screws that hide beneath the surface so that the entire surface can be completely exposed for cleaning and bluing. When finished, blued screws will replace the work screws.
All surfaces to be blued are then wiped with a solution of alcohol and whiting – a polishing compound of very fine texture. Wiped with a clean dry cloth, they are now chemically clean. From this point on until the bluing process is complete, not a human hand touches a surface to be blued.
“These are bluing racks,” interrupted Mr. Carmody. “They are built to hold a maximum number of pieces, yet allow ample room for air circulation with no chance for parts touching each other. This one is for barrels. We have racks for frames, cylinders, hammers, triggers, extractors, latches, grip safety, etc. All our screws and pins, however, are blued in bulk in those small part furnaces that you see over there.” Matched parts, such as a slide and receiver, are alternately fastened in place in the bluing rack. Racks are stored under uniform heat in closed compartments to keep them sterile and dry.
All this is preparatory to the actual bluing process itself.
Let’s take a look at the bluing room. What do we see? Twin rows of revolving drums – thirty large furnaces and eight small part furnaces.
A bluing run starts the first thing in the morning. A secret mixture of charred bone and primer is put into the furnace. Furnaces are heated up to 500 deg or more to evaporate all moisture. The racks are loaded into the bluing furnaces, the doors bolted. The furnaces slowly revolve. Pyrometers control the heat in all furnaces. Readings are taken every 15 minutes during the five hours it takes to complete the bluing process. Top heat is 650 deg.
The furnace itself is gas fired. Four burners supply the heat and it is interesting to note that the forward burner is larger to compensate for any heat loss through the doors.
The charge used in the bluing process is ground animal bone charred to chemical purity in a bone pot placed into a white hot furnace at 1400 deg hot. Two hundred pounds of bone are charred at a time, burning away all foreign matter.
The primer is bone, soaked in pure petroleum oil. Even the oil is boiled to remove moisture and foreign matter. It must be chemically pure. The primer is what gives off the smoke that keeps free oxygen away from the pieces being blued in the revolving drums. The primer and charred bone are mixed and put into the furnace before the work goes in.
What is the chemistry of bluing, anyway? How does this bluing process impart this handsome and lasting blued steel finish so famous on Colt firearms? Bluing is a combination of carbonizing and oxidizing that by heat, brings the inherent carbon of the steel through the opened pores to the surface. All the coloring is done by heat, no particle of bone ever touches the parts being blued. The smoke given off by the primer expells free oxygen from the drum leaving only sufficient to allow combustion. The primer and the charge control the composition of gas in the furnace, the heavy carbon dioxide shielding the parts from contact with oxygen. All this calls for expert knowledge and experience in mixing the proper proportions of the primer and charge not only to obtain the proper color but to create a smoke that shall be free from moisture. Otherwise, though blued, the pieces would be spotted.”
The picture shows an operator loading a furnace with a rack holding about 80 revolver frames.
Haven and Belden "A History of the Colt Revolver" reprints "A Century of Achievement"
"Frames, cylinders, barrels, slides, receivers and parts come to the bluing room direct from the polishing department. Side plates and cranes are removed. Everything is first given a bath in hot gasoline… gasoline heated to 150 deg F. This removes all dirt particles, dust, or grease that may have gathered on the way down from the polishing room. Hot air is then forced over them to eliminate all presence of moisture – the arch enemy.
After washing and drying is completed, the side plates (revolvers) are put back on. But they are put on with work screws that hide beneath the surface so that the entire surface can be completely exposed for cleaning and bluing. When finished, blued screws will replace the work screws.
All surfaces to be blued are then wiped with a solution of alcohol and whiting – a polishing compound of very fine texture. Wiped with a clean dry cloth, they are now chemically clean. From this point on until the bluing process is complete, not a human hand touches a surface to be blued.
“These are bluing racks,” interrupted Mr. Carmody. “They are built to hold a maximum number of pieces, yet allow ample room for air circulation with no chance for parts touching each other. This one is for barrels. We have racks for frames, cylinders, hammers, triggers, extractors, latches, grip safety, etc. All our screws and pins, however, are blued in bulk in those small part furnaces that you see over there.” Matched parts, such as a slide and receiver, are alternately fastened in place in the bluing rack. Racks are stored under uniform heat in closed compartments to keep them sterile and dry.
All this is preparatory to the actual bluing process itself.
Let’s take a look at the bluing room. What do we see? Twin rows of revolving drums – thirty large furnaces and eight small part furnaces.
A bluing run starts the first thing in the morning. A secret mixture of charred bone and primer is put into the furnace. Furnaces are heated up to 500 deg or more to evaporate all moisture. The racks are loaded into the bluing furnaces, the doors bolted. The furnaces slowly revolve. Pyrometers control the heat in all furnaces. Readings are taken every 15 minutes during the five hours it takes to complete the bluing process. Top heat is 650 deg.
The furnace itself is gas fired. Four burners supply the heat and it is interesting to note that the forward burner is larger to compensate for any heat loss through the doors.
The charge used in the bluing process is ground animal bone charred to chemical purity in a bone pot placed into a white hot furnace at 1400 deg hot. Two hundred pounds of bone are charred at a time, burning away all foreign matter.
The primer is bone, soaked in pure petroleum oil. Even the oil is boiled to remove moisture and foreign matter. It must be chemically pure. The primer is what gives off the smoke that keeps free oxygen away from the pieces being blued in the revolving drums. The primer and charred bone are mixed and put into the furnace before the work goes in.
What is the chemistry of bluing, anyway? How does this bluing process impart this handsome and lasting blued steel finish so famous on Colt firearms? Bluing is a combination of carbonizing and oxidizing that by heat, brings the inherent carbon of the steel through the opened pores to the surface. All the coloring is done by heat, no particle of bone ever touches the parts being blued. The smoke given off by the primer expells free oxygen from the drum leaving only sufficient to allow combustion. The primer and the charge control the composition of gas in the furnace, the heavy carbon dioxide shielding the parts from contact with oxygen. All this calls for expert knowledge and experience in mixing the proper proportions of the primer and charge not only to obtain the proper color but to create a smoke that shall be free from moisture. Otherwise, though blued, the pieces would be spotted.”
The picture shows an operator loading a furnace with a rack holding about 80 revolver frames.
OP
Pig Hunter
Member
Thanks Chris, that is the most information I have ever seen on the process. What I have done is quite similar, but we used a higher temp. This was done on non-critical parts that are not under stress. I need to do more research on heat treat temps.
Chicoine notes (in Gunsmithing Guns of the Old West) Carbonna bluing was accomplished by initially placing the work pieces in a special retort (a large sealed oven, in this case a special rotating furnace) where they were heated to what were called "oxidizing temperatures" of 700-800 degrees (F). The mixture of charred bone meal and carbonia oil was then added to the retort. At this point temperatures were lowered to 500-600 degrees (F) and kept there for several hours, all the while the retort rotated continuously. The furnace was then turned off and allowed to cool, the parts removed and dipped in sperm oil." Perhaps of note (vis-a-vis heat treating), Carbonna bluing was also referred to as a "tempering finish" because it served to combine the tempering of the steel while providing an oxidizing surface finish all in one.
There's more, but while I understand all the words; their combined meaning is best left to those who understand more than just the words.
Ralph Tremaine
There's more, but while I understand all the words; their combined meaning is best left to those who understand more than just the words.
Ralph Tremaine
Last edited:
Watchdog
Member
- Joined
- Apr 6, 2013
- Messages
- 12,511
- Reaction score
- 32,351
Great post! Full of information...most of which I don't understand, but still very informative.
Interesting. The 7-800 degree range is what is used to temper steel for use as springs.
I have messed a little bit with coloring steel with heat. A polished piece of high carbon steel just stuck in an oven at 400f will usually turn kind of gold higher than that the blue color starts to come. But, any oil can cause a color change. Just heat colors it but not very long lasting.
These were some of my early Damascus knives colored with heat
I have messed a little bit with coloring steel with heat. A polished piece of high carbon steel just stuck in an oven at 400f will usually turn kind of gold higher than that the blue color starts to come. But, any oil can cause a color change. Just heat colors it but not very long lasting.
These were some of my early Damascus knives colored with heat
Attachments
Last edited:
This is how DWM / Mauser produced the straw colour used for the small parts on Lugers. Just heat the part to about 450*f for 15 minutes and the "straw" colour will develop. There are charts that will show what colours are produces at what temperatures.
Best regards,
It's a zero atmosphere condition. The temp needed for the deep blue is in the 750/800F range.
Any oxygen from the atmosphere that gets into the bluing chamber,,spoils the finish. The smoke from the oil/bone-char mix exits a tiny vent in the chamber to continually prevent air from outside from getting in. The reason for an air tight vessel.
Carbonia Oil was the propietary oil of the patented process, thus the name, but it will work with most any oil with varying results. Linseed and even pine tar oil were used.
The hardward industry used the process to blue common fasteners for years and used cheaper oil. Even Winchester used linseed when quantity bluing small parts like washers, pins, screws, plungers, ect.
We experimented with several different methods, set=ups, temps, times, ect till we started to get results. Absolutely clean parts are a necessity. The rotation of the furnace was also part of the process as it gently sifted and dumped the char over the parts to burnish them during the process and avoid hot and cold spots.
Manualy turning a chamber every 15 or 20min during experiments was a big jump in getting results as I recall. Parts were wired to a rack inside, small paddles of sorts welded to the removable rack helped to lift and sift/pour the char over the parts. Sort of like a slow rotating cement mixer for lack of a better explanation.
Air gets in,,reddish colors and hazzy casts of poor blued areas on the parts. White specks,,oil or moisture on the parts (silicone oils are the toughest to clear from parts).
Moisture can most likely come from the char and oil mix when first placed into the chamber. The char and the oil to some extent absorb moisture from the air. When placed in the chamber, sealed and warmed, the moisture first starts to evaporate from the char but does not leave the chamber. It seems to go right onto the parts then evaporates. Those evaporation marks come back as tiny white specks (no blue).
To avoid,,warm the char and oil before use to drive off any moisture.
We warmed the char up for use in case hardening too for the same reason. That use to sit in a big steel box on top of the shut down oven(s) at the end of the day for use the next AM. That overnite drying did the trick.
l
Like CaseHardening,,it's not a particularly difficult process,,just one that you need to figure out a very planned and precise detailed way that nets results. Then stick with that.
Just what I can pass along..
Any oxygen from the atmosphere that gets into the bluing chamber,,spoils the finish. The smoke from the oil/bone-char mix exits a tiny vent in the chamber to continually prevent air from outside from getting in. The reason for an air tight vessel.
Carbonia Oil was the propietary oil of the patented process, thus the name, but it will work with most any oil with varying results. Linseed and even pine tar oil were used.
The hardward industry used the process to blue common fasteners for years and used cheaper oil. Even Winchester used linseed when quantity bluing small parts like washers, pins, screws, plungers, ect.
We experimented with several different methods, set=ups, temps, times, ect till we started to get results. Absolutely clean parts are a necessity. The rotation of the furnace was also part of the process as it gently sifted and dumped the char over the parts to burnish them during the process and avoid hot and cold spots.
Manualy turning a chamber every 15 or 20min during experiments was a big jump in getting results as I recall. Parts were wired to a rack inside, small paddles of sorts welded to the removable rack helped to lift and sift/pour the char over the parts. Sort of like a slow rotating cement mixer for lack of a better explanation.
Air gets in,,reddish colors and hazzy casts of poor blued areas on the parts. White specks,,oil or moisture on the parts (silicone oils are the toughest to clear from parts).
Moisture can most likely come from the char and oil mix when first placed into the chamber. The char and the oil to some extent absorb moisture from the air. When placed in the chamber, sealed and warmed, the moisture first starts to evaporate from the char but does not leave the chamber. It seems to go right onto the parts then evaporates. Those evaporation marks come back as tiny white specks (no blue).
To avoid,,warm the char and oil before use to drive off any moisture.
We warmed the char up for use in case hardening too for the same reason. That use to sit in a big steel box on top of the shut down oven(s) at the end of the day for use the next AM. That overnite drying did the trick.
l
Like CaseHardening,,it's not a particularly difficult process,,just one that you need to figure out a very planned and precise detailed way that nets results. Then stick with that.
Just what I can pass along..
A gun smith friend trained at the S&W factory also observed the bluing process as using cement mixer-like furnaces.
“I can tell you this that the different steel in the revolvers will blue with slightly different colors. I have seen it many times with the old carbona hot blue. That is one of the reason the factory changed in the late 1970s to the penetrate bluing process.” Roy
“I can tell you this that the different steel in the revolvers will blue with slightly different colors. I have seen it many times with the old carbona hot blue. That is one of the reason the factory changed in the late 1970s to the penetrate bluing process.” Roy
Last edited:
What about using an inert atmosphere oven. My heat treat oven is electric and I can flood it with an inert gas like argon. Nitrogen might even work and it helps dispel water. I have never tried it for coloring. The colors above were produced in an kitchen oven or with a small torch.
A couple I used to work for worked for a industrial heat treating company and they had some large inert ovens that were used to treat stainless steels. One of them being either Gerber or Leatherman parts. I don't know how big or much stuff your trying to do, but, an electric oven that went up to 800f and sealed up would not be that hard to make. It doesn't really have to seal up 100% if you keep a bit of positive pressure on it with your inert gas.
Good luck with your experiments and process.
I do have to seriously think that some of the stuff in the smoke itself effects the coloring. It can't be just about keeping an inert atmosphere.
A couple I used to work for worked for a industrial heat treating company and they had some large inert ovens that were used to treat stainless steels. One of them being either Gerber or Leatherman parts. I don't know how big or much stuff your trying to do, but, an electric oven that went up to 800f and sealed up would not be that hard to make. It doesn't really have to seal up 100% if you keep a bit of positive pressure on it with your inert gas.
Good luck with your experiments and process.
I do have to seriously think that some of the stuff in the smoke itself effects the coloring. It can't be just about keeping an inert atmosphere.
"...I do have to seriously think that some of the stuff in the smoke itself effects the coloring. It can't be just about keeping an inert atmosphere..."
It is the combination of the bone char and the oil, it's smoke and the temp that produces the blue.
Simply placing parts in a zero atmosphere and running the temp to 650 will give you the same bright blue as Nitre Blue,, another zero atmosphere blue process.
Nitre Blueing salts taken up to betw 750/800 will give a very deep blue/black that mimics Carbona Blue on most steel.
A few purveyors of Carbona Blue use that latter method good or bad.
I use if for small parts, trigger guards, floor plates ect where the look is needed sometimes in restoration.
Temp is very critical at these levels and a bit too much (more) and you spoil the finish.
There seems to be a lot of similaritys to these finishes but yet they are distant in their application and materials.
The keeping the outside atmosphere out of the vessel during the 'Carbona' process is key in getting a complete and even coverage with no variation in color, blotches, hazy spots on individual pieces.
Yes some steel alloys or HT differences will blue differently from one to another.
Winchester had a difficulies at times matching colors betw the M12 and M42 frames and their frame extensions when they still used the process.
They abandoned the process in full and went to hot salt DuLite in late 38 or '39 on all their guns.
The Carbon Blue had a tendency to flake off on the Win lever action receivers..so many of them around look 'in the white' while the bbl still has near all the (rust) blue in tact yet. Just something about the steel and HT of it.
FWIW,,charcoal bluing is another related bluing process. Done in the embers of burning charcoal, the piece is covered in the 'coal'.
Two things are similar,,the charcoal cooks at the nice temp of approx 850F if you have the correct wood type,,,,and covering the piece with the burning char keeps it in an atmospher free envelope as the char gives off CO as it burns.
Several different techniques were/are used to get even results inluding burnishing the pieces occasionally with different substances (chalk, lime, ect). Some coat the pieces with a very thin coating of different types of oil after burnishings,,some don't.
Techniques vary as they do with any of these finishing processes wether case hardening, stock finishing or painting a picnic table.
The pit method of building the charcoal fire is often mentioned in M/Loading bbl finishing. It was done and succesfully.
The reason for a 'pit' was to put the char fire down below ground level and keep it from being affected by drafts and wind. You want the char to burn at it's natural rate of 850f. Fanning the fire increases the intensity and ruins the finish and process by inducing too much heat.
You can actually get a 'heat scale' finsh that way and with a bit of air getting at the bbl or parts. Not unattractive in itself I guess,,but deffinetly not a charcoal blue and not fit for precision cartridge guns. The excessive heat involved is a question also.
The only factory long gun bbl I can think of quick off hand that was charcoal blued was the Henry rifle. There were probably others.
It is the combination of the bone char and the oil, it's smoke and the temp that produces the blue.
Simply placing parts in a zero atmosphere and running the temp to 650 will give you the same bright blue as Nitre Blue,, another zero atmosphere blue process.
Nitre Blueing salts taken up to betw 750/800 will give a very deep blue/black that mimics Carbona Blue on most steel.
A few purveyors of Carbona Blue use that latter method good or bad.
I use if for small parts, trigger guards, floor plates ect where the look is needed sometimes in restoration.
Temp is very critical at these levels and a bit too much (more) and you spoil the finish.
There seems to be a lot of similaritys to these finishes but yet they are distant in their application and materials.
The keeping the outside atmosphere out of the vessel during the 'Carbona' process is key in getting a complete and even coverage with no variation in color, blotches, hazy spots on individual pieces.
Yes some steel alloys or HT differences will blue differently from one to another.
Winchester had a difficulies at times matching colors betw the M12 and M42 frames and their frame extensions when they still used the process.
They abandoned the process in full and went to hot salt DuLite in late 38 or '39 on all their guns.
The Carbon Blue had a tendency to flake off on the Win lever action receivers..so many of them around look 'in the white' while the bbl still has near all the (rust) blue in tact yet. Just something about the steel and HT of it.
FWIW,,charcoal bluing is another related bluing process. Done in the embers of burning charcoal, the piece is covered in the 'coal'.
Two things are similar,,the charcoal cooks at the nice temp of approx 850F if you have the correct wood type,,,,and covering the piece with the burning char keeps it in an atmospher free envelope as the char gives off CO as it burns.
Several different techniques were/are used to get even results inluding burnishing the pieces occasionally with different substances (chalk, lime, ect). Some coat the pieces with a very thin coating of different types of oil after burnishings,,some don't.
Techniques vary as they do with any of these finishing processes wether case hardening, stock finishing or painting a picnic table.
The pit method of building the charcoal fire is often mentioned in M/Loading bbl finishing. It was done and succesfully.
The reason for a 'pit' was to put the char fire down below ground level and keep it from being affected by drafts and wind. You want the char to burn at it's natural rate of 850f. Fanning the fire increases the intensity and ruins the finish and process by inducing too much heat.
You can actually get a 'heat scale' finsh that way and with a bit of air getting at the bbl or parts. Not unattractive in itself I guess,,but deffinetly not a charcoal blue and not fit for precision cartridge guns. The excessive heat involved is a question also.
The only factory long gun bbl I can think of quick off hand that was charcoal blued was the Henry rifle. There were probably others.
The "bible" on heat treating is the heaters guide. It is about $300, but you can find some of it on the net.
Most carbon steels without a bunch of nickle or chrome need to be taken to 1500f then quenched to harden. If you forge it you really need to normalize before you harden it. Either take it to 1500f and then slow cool by leaving the oven cool on its own or quench then reheat to 1500f and quench again. Tempering after that is also critical. To get the best temper 2 cycles of 2 hours at your temper temperature. Near full hardness will be retained at 350 f and working down from there. A spring is tempered at about 750f. Many frame parts are dead soft, but there is a difference between non heat treated and heat treated even at the same hardness. Hardening causes thee steel to form a different structure (martensite) than untreated steel (pearlite). Martensite is much tougher even at the same hardness as pearlite. Ordinance steel like 4140 and the like responds to this type of treatment because of its low alloy content.
Carbon, 0.40%
Manganese, 0.75-1.00%
Chromium, 0.80-1.10%
Molybdenum, 0.15-0.25%
Adding nickle and especially chrome causes the needed temperatures to harden to rise and in addition you need to let the steel soak at the higher temp because the alloy makes it harder for the carbon to move into solution. Usually around 1800f or more depending on the alloy and at least 30 min. To do this you need to keep the piece in an inert atmosphere in some manner to keep the steel from decarbonizing. When I do stainless steel blades I enclose them in an envelope of 309 stainless foil. Interestingly high alloy steels do not need to be quenched as rapidly because once again the carbon has a harder time moving. Mostt stainless steels are air hardening, but I clamp my blades between to large aluminum plates.
Last edited:
DWalt
Member
"Winchester had a difficulties at times matching colors between the M12 and M42 frames and their frame extensions when they still used the process. They abandoned the process in full and went to hot salt Du-Lite in late 38 or '39 on all their guns."
Most firearms manufacturers (also manufacturers of other steel items) adopted the hot dip black oxide bluing process in the 1930s, under such trade names as Du-Lite and Black Magic. Ned Schwing's excellent book "Winchester Slide Action Rifles" (Krause, 2004) discusses Winchester's bluing operations in some detail. In the pre-WWII period, before the black oxide dip bluing process, Winchester used what Schwing calls "Carbonium" bluing (but Winchester called it "Machine Bluing"). His description of it is similar to "Carbonia". I'll greatly abbreviate Schwing's description of Winchester's Carbonium (or Machine Bluing) process:
-It used a gas-fired furnace five feet in diameter and seven feet in length. (Furnace rotation is not mentioned)
-Animal bone (sic) and sperm oil were mixed together and allowed to heat inside the oven at 475 degrees F.
-Parts were placed in the oven which was then gradually heated to 850 degrees F. and allowed to remain there for four hours.
-Oven temperature was gradually lowered to 500 degrees F.
-Parts were then removed, quenched in oil (type not specified), and allowed to dry.
Small parts were similarly blued except that pine tar was used instead of sperm oil.
Winchester also used a "Niter" bluing process for some components, which involved placing parts in a "hot solution" (Schwing's description, 600 to 1000 degrees F.) of sodium and potassium nitrates. I suspect it was really a molten salt bath rather than an aqueous solution.
In 1939, Winchester began a changeover to using black oxide dip bluing, Schwing says it was Du-Lite. This was a double-dip procedure. Parts were first dipped into the bluing salt solution bath held at 300 degrees F. for 30 minutes, then into another bluing salt solution bath held at 310 degrees F. for an additional 30 minutes. This was said to produce a darker and more uniform bluing than a single dip into the bluing bath. The various black oxide bluing baths such as Du-Lite and Black Magic are essentially aqueous solutions of sodium hydroxide and sodium nitrate and/or potassium nitrate.
Schwing's book is a little hard to come by and is somewhat costly (around $200) on the used book market. But it is worth it if you happen to be a Winchester slide action rifle collector as it is extremely thorough in its treatment of the topic.
Most firearms manufacturers (also manufacturers of other steel items) adopted the hot dip black oxide bluing process in the 1930s, under such trade names as Du-Lite and Black Magic. Ned Schwing's excellent book "Winchester Slide Action Rifles" (Krause, 2004) discusses Winchester's bluing operations in some detail. In the pre-WWII period, before the black oxide dip bluing process, Winchester used what Schwing calls "Carbonium" bluing (but Winchester called it "Machine Bluing"). His description of it is similar to "Carbonia". I'll greatly abbreviate Schwing's description of Winchester's Carbonium (or Machine Bluing) process:
-It used a gas-fired furnace five feet in diameter and seven feet in length. (Furnace rotation is not mentioned)
-Animal bone (sic) and sperm oil were mixed together and allowed to heat inside the oven at 475 degrees F.
-Parts were placed in the oven which was then gradually heated to 850 degrees F. and allowed to remain there for four hours.
-Oven temperature was gradually lowered to 500 degrees F.
-Parts were then removed, quenched in oil (type not specified), and allowed to dry.
Small parts were similarly blued except that pine tar was used instead of sperm oil.
Winchester also used a "Niter" bluing process for some components, which involved placing parts in a "hot solution" (Schwing's description, 600 to 1000 degrees F.) of sodium and potassium nitrates. I suspect it was really a molten salt bath rather than an aqueous solution.
In 1939, Winchester began a changeover to using black oxide dip bluing, Schwing says it was Du-Lite. This was a double-dip procedure. Parts were first dipped into the bluing salt solution bath held at 300 degrees F. for 30 minutes, then into another bluing salt solution bath held at 310 degrees F. for an additional 30 minutes. This was said to produce a darker and more uniform bluing than a single dip into the bluing bath. The various black oxide bluing baths such as Du-Lite and Black Magic are essentially aqueous solutions of sodium hydroxide and sodium nitrate and/or potassium nitrate.
Schwing's book is a little hard to come by and is somewhat costly (around $200) on the used book market. But it is worth it if you happen to be a Winchester slide action rifle collector as it is extremely thorough in its treatment of the topic.
Last edited:
cgt4570
Member
I also read somewhere once that some of the gun companies insisted on only using human bones for the bone charcoal! It was sourced from third world (at that time) countries such as Egypt where there were tons of ancient slave and lower class grave sites to be found.
***groan***
Attachments
OP
Pig Hunter
Member
And for case colors to be authentic you need to use the fresh urine of a female dromedary after it's first heat cycle, applied during a full moon. For those who have contributed, thank you. As I said experimentation will continue. The reference materials will be valuable. It's too bad those of us that want to try to use traditional methods have to re-invent the wheel.
DWalt
Member
I have never heard of that, but it is a fact that in the 19th century there were huge amounts of Egyptian mummy linen wrappings exported to Europe and used there for making paper. I suppose that after the mummies were unwrapped, the Egyptians could have ground up and shipped all the leftover mummy bones to Winchester, S&W, and Colt. No reason it couldn't have happened.
Last edited:
Roy Jinks mentioned that the unavailability of human bone meal meeting S&W standards was a key factor in S&W discontinuing the process, and if I remember correctly, India was mentioned as the source.
