Talk:Bluing (steel)

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Heat treating[edit]

How does this relate to the blue finish one gets by simply heating steel or to "blue srping steel"? (See martensite). —BenFrantzDale 05:20, 6 December 2005 (UTC)

In gunsmithing terms that'd be "salt bluing," which was always rather rare, and more common in Europe than in North America. Pre-World-War-I production Lugers from the Mauser plant often had many of the small parts salt-blued (that is, immersed in molten salt until the martensite composition gave the desired surface color). It was both a heat treatment and a cosmetic coloring process, and the uniformity of color on the small parts was intended to show off the skill and technical prowess of the manufacturer.

The process of heating steel after it has been hardened, known as tempering, can impart colors to steel ranging from pale yellow "straw" to very light blue. When done for decorative purposes it can be referred to as "Fire bluing", see the article on tempering for pics and more. — Preceding unsigned comment added by (talk) 04:26, 21 May 2012 (UTC)

Please quit using an end ) in the URL as HTML does not like it. Captain Cummings ( (talk) 23:54, 2 June 2008 (UTC)). Thanks

I would like to add some comments about how this process related to blacksmithing. I believe that the process that blacksmiths use to blacken their forged pieces results in the same finish. After hot forging the piece will be naturally corroded. Allowing it to cool to the point that is can be coated with wax and then allowed to cool completely results in a hard and very black finish. Some people, me included, believe this how blacksmith got their name. They worked the black metal. I am not a metallurgist or chemist so I am not certain that this process results in the same finish. Could someone with more technical knowledge confirm that it is the same finish?

Dc6482 (talk) 18:44, 5 May 2011 (UTC)

That's not bluing, it's just laziness. It certainly doesn't give a particular hard, black or corrosion resistant finish.
Mild steel (unless it's bright drawn) is usually supplied with this black oxide finish. However that's produced by a rolling mill, not by hand forging. It's somewhat resistant, and is very black. When wrought iron is hand-smithed, you'll also get something of a black oxide finish. When mild steel is smithed though, the scale produced isn't thick enough or strong enough to make a useful finish. Wax is always applied cold. Whilst many smiths do just wax over hammer scale, it's a bit shoddy and certainly not a resistant finish. A better finish, and very popular, is to apply a hot oil finish. This can be brown, blue or black, depending on the oil used (vegetable, mineral motor oil, used mineral motor oil). It's quite a good finish for indoor use, although it's not as good as bluing for weather resistance.
Traditional smithing's finish for gunsmithing was browning, not bluing. Deserves an article, if we don't already have it. It's mostly a controlled rusting to produce the unhydrated Fe(III) oxide (brown rust). This is produced carefully, brushed and oiled. Unlike most rust, it can then produce a surface that's fairly impermeable and doesn't rust further (unlike the common hydrated red rust).
Neither of these are bluing (even a blue oil finish). Bluing is a chemical change to the surface, brought about by supplying more than just oxygen. Andy Dingley (talk) 20:13, 5 May 2011 (UTC)
Browning (steel) redirects here, by the way. Huw Powell (talk) 03:24, 1 August 2012 (UTC)


I think the modifier on the title (steel) should be changed, because this process can be applied to other metals. For instance, the military documents in the references section state that it can be applied to wrought iron. Perhaps the modifier should be metal or ferrous metal. --Wizard191 (talk) 22:42, 7 September 2008 (UTC)

Black oxide[edit]

I'm considering making a black oxide article, however, this article seems to have a lot of info on it. Upon reading the article I'm not sure if they aren't the same thing. Also, the military references refer directly to black oxide. So I guess my question is: 1. are they the same? 2. If not what's the difference? --Wizard191 (talk) 23:13, 7 September 2008 (UTC)

Black oxide is a true gun bluing. However, not all gun bluing is black oxide based. As you note, the MIL references and standards mentioned do refer directly to black oxide. Take a look at the Parkerizing and Phosphate conversion coating articles; one is on historical Parkerizing, and the other is on modern phosphate coatings. Perhaps the same kind of treatment would be worth applying here, too. "Bluing" is used more in an historical firearms terminology usage, whereas "black oxide" is used more in modern engineering terminology, for firearms as well as for non-firearms. Yaf (talk) 01:33, 8 September 2008 (UTC)
OK...let me make sure I understand this correctly. Bluing is just a firearms term for a black oxide coating applied to guns. However, it is used. Yes? If this is the case perhaps the modifier on the title should be changed to "guns".
Just for clarification I am looking at black oxide from the engineering side of things, and know nothing about firearms or its terminology. --Wizard191 (talk) 11:59, 8 September 2008 (UTC)
Black oxide is but one type of bluing for firearms; there are other types of bluing used on firearms, too. (Hot bluing vs. cold bluing, and hot bluing versus "hot and cold" mixed bluing, for example.) Black oxide is also used to refer to thicker bluing that is black oxide based. "Bluing" is also used to refer to an historical protection against corrosion for steel parts in general, such as used in wind up clocks, firearms, internal gears in fishing reels, and other similar precision-machined steel parts that are subject to corrosion. So, bluing is not a "gun-only" terminology. Because bluing does not change the dimensions of steel parts by an easily-measured amount, it has long been used to achieve corrosion resistance for steel parts, while always ignoring any tolerance buildup for mechanical dimensions of blued steel parts versus the same unblued steel parts. On the other hand, black oxide coatings typically refer to coatings that are much, much thicker, and that often do change the measured dimensions of protected steel parts by an easily measurable amount. So, "Bluing (firearms)" would not really be an accurate title. Why not have an article on "Bluing" and another article on "Black oxide coatings", with the historical usages centering on "Bluing", and with the modern usages centering on "Black oxide coatings", with a differentiator disclaimer at the heading of the article that was worded similar to what is used in the Parkerizing and Phosphate conversion coating articles. This would make the encyclopedia more useful to both non-technical users (who would be looking for bluing) and for technical users (who would be looking for black oxide coatings). With the appropriate discrimination wording line at the head of each article, this would work well. Yaf (talk) 18:11, 8 September 2008 (UTC)
Having two articles is perfectly fine by me. I was going to make a "black oxide" article, but then I found this one, and wasn't sure if it was the same thing, but you have cleared that up for me. I'll go ahead and make the article then. Thanks for the info! --Wizard191 (talk) 18:25, 8 September 2008 (UTC)
Yikes! My laziness seems to have set a precedent. I was the one who made the link between Parkerizing and Phosphate conversion coating, realizing that they were the same thing. I actually think they should be merged, but I was mostly just lazy. I foresaw a dispute on the names, because it "phosphate converstion" is easily the more common name in industry, but "parkerizing" appears to be better known on Wikipedia. So I just put in hatnotes so people would clue in to also look elsewhere. I also think black oxide and bluing (steel) should be merged. I don't really want to lead that effort, but please don't enshrine my past mistakes.--Yannick (talk) 15:52, 13 June 2009 (UTC)

Hot Bluing?[edit]

I have tried two different ways of hot bluing; both failed. I then read it has to be done under pressure, and can be dangerous. Why not mention this?Tintinteslacoil (talk) 00:48, 13 March 2009 (UTC)

This seems a cop-out to me -- if one process is done under pressure, or different results are done under pressure, this should be mentioned -- there is a BIG difference between "Take the batter and drop it into hot oil. . . ." (Donuts) and "Take the batter and drop it onto a well oiled flat piece of steel. . ." (pancakes) -- etc. THAT is a 'COOKBOOK'. I disagree with the concept of giving 'instructions' -- and explaining the process. "cook under pressure" will give you a Bagel, OR will give you a type of dumpling -- Which is it? I would HOPE that Wilipedea would be ALLOWED to tell the readers the difference -- or the Jack-booted thugs of small brains, sharp teeth and beady eyes will soon take over. I wonder if the censor has a clue about how many kinds of 'bluing' there are - or that various bones from various animals give predominately different colors -- how DO you get more "red" in the "blue", or more "straw" or more or a 'lighter' or 'deeper' blue? Very little is known about Color Case Hardening because most recipes are handed down from father to son. I have part of a book that talks about the difference between one year old lamb ribs, or 8 month old ham hocks smoked in hickory for 3-5 months -- and so on through various animals and bones, and how long they need to set out before you use them -- "Must not stand more than half a season. . ." to "3 Seasons in a sunny location seems to give the most metallic blue. . . " I ALSO don't see the place of oxidation in the 'harness' or 'coloring' of the metal. One person found that while the metal was still hot, it was best to use a billows to blow air between the metal being blued and the bucket it's about to be dropped into: "Hold the magazine cover no further away than 3/8th of an inch above the water and that instant you begin to see the color change, pump on the foot billows directing air between the metal and the water. I am told that this 'fixes' the finish to the metal, and turns it a (the discussion was mutton rib and lower limb bones mixed with some calf-clavicle)a light blue with streaks of ruby red floating on top of the blues and straws"..... the idea being that the introduction of oxygen in the presence of hydraulic steam at the exact temperature where you can 'feel it change' is VERY useful to people seeking the difference between various types of color in hard cold steel bluing -

There is reference to using wood chips - and each wood will give a different hugh when burned to charcoal -- Just as ANY beginning BBQ-er if Apple wood and Peach wood -- even when burned to black charcoal give off a different flavor for the wood-- or if you BBQ in black-oak, THEN follow that by apple and Cherry -- if the flavor is the same is starting with Cherry, and then switching to some Apple and finishing off with a very heavy black-oak smoke -- same woods, same lengths of time, only you change the order.

How would one make oat-meal -- Well first you put the oats on a fire, then you get a pot and fill it with water and bring it to a boil, add the oats, and cook for 20 minutes is FAR different than Boil water, add oats, then stir and cook oats for 20 minutes. NEITHER is a recipe -- but when I wanted to find out what Haggis was, it sure was handy to look it up and see that it was sheep stomach stuffed full of innards (lungs, liver, kidney, etc) the packed solid with oat-mean and sewn shut and tossed into a fire, preferably underground -- and there you have it -- the National Dish of Scotland.

So -- let's keep this an encyclopedia and not go around pretending it's not, or having someone say -- yeah, that "IT'S NOT A COOKBOOK" - especially when **I** want to know what color case hardened bluing is - and telling me that it is simply a 'black' bluing is like asking how they get the blue in Crayons and being told "Well, this old man, a Magician employed secretly by Crayola, takes just a little bit of blue from the sky and mixes it in with the wax like substance -- or While the color wheel is spinning, an elf with VERY fast hands snatches a color from the wheel, and puts it back before it's missed -- so when the wheel stops, the blue is still there!

A little knowledge is a dangerous thing, and someone who enforces rules they don't understand by hiding behind other rules they don't understand -- just doesn't cut it when it comes to people who DO know that there's a difference, but not exactly what it is --

I'll bet every old-time rilfe smith has his private recipe that works for him -- so many can pick up a rifle or pistol and say - Oh! Gary Davis blued this one! -- because Gary Davis has his own formula you will pry from his cold dead hads (IF you can get his safe open). Rust is NOT the same as 'black' -- and the color in color case hardening seems to do do with the amount of oxyigen and a bit of steam that work together to BOND the gas that forms between the water in the bucket and the barrel of the rifle and causes it to stick tight and repel water enough that it can last 100+ years if taken care of correctly.

About all I got out of this is that is should be a Ferris material, though I'm not certain about that. Just like Grandpa told me his Winchester 94 shifted 1/2 MOA at 100 yards after the first 10 rounds, so keep that barrel at a Kentucky of 1/4 MOA for an hour after that last shot -- but that's THAT gun,not Winchester 94's in general, and it had a VERY low SN, let's say within the first 100,000 or less. Someone needs to patrol these pages and make sure the truth is not being cut off, or misrepresented as it was here - and then 'ended' by saying 'this is not a cook-book, but how many people knew that different animals and different bones from those animals would change the color of the metal? Certainly not the firearms 'expert' who squashed the article. Heck, just this summer or the one before an NRA armorers school had a student do a project and found out it was OXYGEN and not some other active or inert gas that cased the color change. Firearms bluing is where there is still PLENTY of room for Alchemy since we have moved away from 'bluing' to more 'stable' and 'bonding' substances, like parkerizing, or even 'electroplating' parts so they'll out live the metal they encase! So let's all hear it for 2 sheep vertebrae, a veil femur, 1 ham-hock smoked in 2 parts hickory and 2 parts apple wood, heated to a whiteish red smoked over a hot oak fire, then held over a bucket of water where you made some peach wood 'tea' the night before -- and after you 'feel' it begin to cool, pump up that old billows made from horse hide and direct that copper and deer skin nozzle right between the water and the receiver - and let go the entire receiver the absolute SECOND it stops glowing red (because you KNOW the difference between the hallucinogenic cherry red, and the REAL cherry red) and just let it drop into that bucket of ICE COLD water - even if you had to go to the ice shed and brush aside some sawdust and get a chunk of real ice to get it cold enough -- and you'll have ruby red and brilliant emerald green that glows at you ALL night.

So let's not worry about what the exact pressure is, just knowing that some bluing happens under pressure and some doesn't is a VERY important piece of BASIC knowledge and I don't need a goody-goody two-shoes to tell me what the pressure is, I can find out if I need to -- This is NOT mean to be an ad hominum attack since I don't even care if the person name is real or not -- only that he doesn't know what he's talking about and that he's trying to keep me from finding out the truth! Pgalioni (talk) 22:00, 28 March 2011 (UTC)

Wikipedia is not a how-to manual. We don't give instructions and, by the same token, we do not offer advice about health or safety for those attempting to do it themselves. Kafziel Complaint Department 01:09, 13 March 2009 (UTC)
Hot bluing is extremely sensitive to certain impurities, and to properly cleaning the metal of all oil residue prior to attempting to blue it. If some specific impurities are present, or if all oil is not carefully removed, then the hot bluing always fails. If an adequate amount of water is not present, then the bluing fails, too. If the water contains certain minerals, depending on the exact mix, the bluing can fail. Distilled water is generally a good idea. Bluing does not have to be done under pressure. As for dangerous, yes, bluing can be, especially for cyanide based recipes. Suggest further study of some of the older treatises be done, as they are much better at describing the process and how best to overcome the problems. That said, Wikipedia is not a how-to guide, as noted above. Yaf (talk) 03:37, 13 March 2009 (UTC)

Volume Change of Iron Oxide[edit]

I was doing some calculations based on the beginning statement: "the black oxide of iron, which occupies the same volume as metallic iron." According to the Pilling-Bedworth ratio,, this statement is not true. It has a volume change of about 2. I suggest that we change it unless I made a mistake somewhere.

Tycedi (talk) 18:03, 1 November 2010 (UTC)

I agree. It's not true. There's LESS volume change with magnetite, but there's still a volume change. Tarchon (talk) 00:24, 1 August 2013 (UTC)

Niter bluing[edit]

"This is not a chemical means of bluing." That makes no sense. You hang it over fuming chemicals but it's not "chemical"? Tarchon (talk) 00:24, 1 August 2013 (UTC)

That jumped out at me, too. Using hot salts to convert Fe into FexOx is certainly a chemical process. I don't know if it's a typo, or a confused author. Steve8394 (talk) 19:09, 23 August 2014 (UTC)