Nitre Bluing Basics
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- Опубликовано: 5 сен 2024
- Nitre bluing is a process for producing a colored patina on metal parts. The classic color is "peacock blue." But nitre bluing is capable of producing yellow, brown, blue, purple and silver. Knife maker Walter Sorrells shows how it's done.
More at:
Instructional videos: www.waltersorre...
Tactix Armory: www.tactixarmor...
Walter's Instagram: walterstactix
Tactix Armory Instagram: tactixarmory
Twitter: @WalterSorrells
Facebook: / waltersorrellsblades
Patreon: / waltersorrells
Dang Walter, that multimeter has seen better days. Obviously one dedicated to shop use, and many years of it. Thanks for your expertise in ALL your vids, love them. Just another Guy in Tucson
Also exactly the explanation I've been wanting. Several smiths in Russia turn out beautiful blue blades, and I figured it was Nitre bluing, but I also figured it was only suitable for art blades. Thanks for confirming that! Still a beautiful effect.
that is a gorgeous set of damascus!
This is exactly what I've been wanting to see! Thank you so much for showing this!
almost everything Ive ever wanted to know in knifemaking or general tool craft, you have done a video on. thank you for everything you do for the up and coming knifemakers/makers in general.
finding you on patreon to donate to the channel
Just fyi you can use hot niter bluing on D2 because the 600 degree temp you blue at is the same temp you temper the steel at after hardening. But yeah it's too hot for regular carbon steel or even like S7 because you can basically anneal alot of the strength out of the blade. Check out time/temp charts for the steel you are using and pay attention to the post heat treat temper instructions and you should be good.
You hit all the highlights listing types of bluing, but there's one to add to your list, not because it's a viable home shop process, but because it's rare and cool and worth learning about for the gun nerds out there. Carbonia bluing.
The process is basically to suspend the metal in the middle of a slowly rotating drum containing charcoal (and/or bone charcoal) and whale oil (or similar). This rotating drum was heated in a furnace to around 600 degrees and the combination of contact with the coal/oil and the heat imparted a deep blue black as it did a sort of final polish and temper on the steel. This process is what started Colt's reputation for their bluing, Smith & Wesson as well to a degree. The process is conceptually simple, but really hard to execute correctly, and Doug Turnbull is pretty much the only guy around who has worked it out in the modern era.
This is not to be confused with the post-war colts, which also had famously good bluing, but that was achieved by nitre bluing on *very* finely hand polished pieces.
I realize my comment is pretty long, but you're talking about an art that has nearly died, and will soon be forgotten.
I'm passing along a couple of things I know about it, with the hope that you can make use of what I learned, and pass it on to the next guy.
I've always known this to be the old method of color case hardening.
Not too many folks around today who know anything about it.
The bone & antler have already been pyrolized before packing the parts in them. They're really not much more than carbon & a few non volatile compounds that degrade at very high temperature.
In an oxygen free environment, such as the metal box everything is packed into, carbon migrates from the pyrolized bone & antler contacting the parts, and gets trapped in the matrix of the steel.
It's a lot like a single heat of bloomery steel, when you're turning it into high carbon steel.
Due to the relatively low temperature, and relatively solid state of the carbon, the penetration of the casing is only a few thousandths thick.
It's durable as all get out though.
You can still find pre civil war muzzleloaders with color case hardening done this way, and it still looks nearly as good as the day it was fired.
You can also add other stuff to the mix of antler & bone.
Turtle shell is a good one.
So is a little anthracite. Not too much, because it does still contain volatile compounds.
The more materials you put in your mix, the more colors you'll get.
The thing I switched to, because it isn't as difficult to source and seems to work better, is used diesel engine oil. The dirtier, more used up, and thicker the better.
Keep it in a metal can with a lid.
Just heat up your parts, drop 'em in the oil, and temper them back.
The outside casing won't temper, and you don't want to grind it down to see what color the bare metal is, so you have to use an oven with a good thermometer.
This method gives a black case hardening (graphite color if it's buffed out) that's nearly twice as thick as the antler & bone method, but just as durable.
@@kaisersose5549 Nice write-up, and you're right that good color case hardening is fading from our collective know-how. A real shame because it's functional, and beautiful, when done well. I'm always keen to hear from folks with experience in these mystical arts.
Doug Turnbull still does a really nice job of it, and there are a few folks out there like yourself who are keeping it alive and experimenting. I know one gentleman who, and this is going to sound crazy, will pyrolize strips of leather after soaking them in dog urine. He does nice looking work, so who am I to question, but better him than me on that process.
However, the process I was originally describing is not a color case hardening in the same vein as what you're describing.
The Carbonia bluing method I was talking about uses similar components - various carbon bearing mateirals - but tumbles them around in a furnace like clothes in a dryer, with the part suspended in the middle. The results of the process were a rich, deep, even blue-black color, rather than the swirling, colorful patterns you typically see in color case hardening. It also didn't get hot enough to harden steel, so it was a purely cosmetic process.
Unfortunately, being a fairly industrial process, it's essentially out of reach for the little guys, so it basically died out when the big factories switched to more economical processes like rust bluing, parkerizing or hot salt bluing.
I worked part-time in a Gunsmith shop several years ago. Hot, Corrosive Salts bluing is no joke.
Thanks mr Sorrells,
I learned a lot from your vids.
Great content, keep up the good work.
Greetings from the Netherlands.
Great info! Thanks Walter!
The blue finish came out beautiful!!
Well done
Thank you very much.
Another great presentation, thanks Walter
Love all the bluing types and case hardening videos!
Awesome Job Walter. Thank you for sharing.
That pyrometer has seen better days Walt!
Think I need to pay a visit to my local gun store to get some supplies so I can have a play with the nitre bluing effect! I love the 'case hardening' effect too but that's a totally different process!
I wish there were more colors but that purple is really nice
Great topic.
Very nicely done, Thank You!
what is the chemical formula of this bluing
its not available in my area but chemicals are available to me and i know how to be safe with them
i did a search and i found sodium hydroxide and potassium nitrate is used
u say sodium nitrate and potassium nitrate i really hope water is used before heating since i know these are used in explosives and are oxidizers
This process "was" used alot in the gun industry for screws and other small rifle and pistol parts. There's nothing better looking (in my opinion) than highly polished gun screws and other small parts Nitre blued...
Great video 👍👍👍👍
As always TOP NOTCH !!!!
Very cool, great vid.
Hello, I have some questions:
1. Does it work on stainless steel?
2. Is the resulting products safe to come into contact with food?
If I do this to refinish a slide, will the slide rails get negatively affected?
Cool 👍
Interesting, thanks.
You mentioned at the end that this usually isn’t suitable for blades, being that the temperature or the oil will mess with the tempering. Tempering cycles are normally around 400ish and an hour or two if I’m not mistaken. Will one minute of exposure here really have a major effect on the hardness of the steel?
Yes it will that's why he said not to do it
Yes it will definitely mess either temper at least on the surface depending on the thickness of your piece, so you’d end up having to grind off the color anyway, and you’d be betting on not enough heat getting through to mess up the center. Someone else mentioned seeing this process on decorative knives ,but they won’t see barely any use, that may be the only time where I personally would deem it acceptable.
Never actually seen anything on nitre bluing before now. Thanks for putting this up. May have to look into this now.
You don't watch Midway videos?...
@@shadowblack1987 Not familiar with them . Pray, tell.....
Wow.
I have two stainless steel filet knives, Gerber and Rapalla, that I would like to get scary sharp for using on fish. I asked a question of Outdoors55 about the difficulties in sharpening SS and he suggested I look at a video of your about knife steels but I cannot seem to find it. Can you direct me to it please. My question was what makes sharping SS so hard to do?
Walter what is the best stainless steel four nights making that is easy to heat treat and hold a edge just as well as 1095
Referring to the white chucks in the pot
Nice, never done it, and now I want too👌 Walter after you etched the parts, do you just neutralize the acid, and dry them before going in the salt...or do you use something like Brasso and 0000 wire wool to remove surface oxidation, clean/ dry again, and then into the salts?
What liquid would you recommend for the bluing quench? Idk if water would would reduce the fresh coating or if oil would over oxidize it into a darker coating
For bluing a blade Rust or Fume Blue.
Same ...was that oil and salts?
Silly question, but would this process ruin the heat treat of a knife if you wanted to blue the whole blade? Or is that what cold blue is for?
He addressed that and said don't do the blade.
I have cold blued a knife is it ok to use it to eat?
Can I do this with stainless steel? My parents just sent me a set of stainless steel utensils that I have no use for but this might be a great way of recycling them.
No dice bro it only works on regular steel.
great video, seems like you know your stuff! Which I was I was so perplexed when you sprayed your parts with wd-40. I've only done cold blue, but its always finished with oil. just seems really odd to apply a solvent at the end rather than an oil to soak into the patina, am I missing something?
you mention the durability is not infinite, how does the durability of cold blue, hot blue & heat blue compare?
WD40 contains kerosene or something similar, doesn't it? It has both solvents *and* oil.
re: safety...I agree with Mike Rowe...'Safety Third'
Was....was that butter? With the salts?
Walter, what was the white blocky substance in the pot with the pink blueing salts?
I suspect it was cut up blocks of a previous batch.
I’m learning how to make swords and in the town I live in there is a really big gun museum that has real Japanese katanas from the 1500’s up to the 1700’s and there must be hundreds of thousands of guns of every type and era not to mention guns that are strange and the Nazi stuff is interesting as is the 1920’s gangster guns.
What was in the pot with the salt?
What else do you melt with the salts? Or is it just the salts themselves? It looked like 2 different components in your pot.
That's the old salts from last time he used the pan. The salts dont go bad.
Can you use this on a hand gun
What were the square white chunks in the pot that started off with the pink salts? As they melted they looked like soap bar bits.
Hi James, the Brownells salts have a pink die in them when new. After you use them the first time and they cool down they solidify into a white solid which is what you see in Walter's video (he shows them in his pan at one point). He has just broken up the used salts and added some new to them, probably to replace the little bit that gets dragged out of the pot with your parts every time. You can re-use the salts over and over. Something to remember when using them, if you leave a temp probe or thermometer in the salts as they cool you won't be removing it until you heat the salts up again. Ask me how I know🤣
yevad99 do you know of any other brand than the brownelles salts, I can’t find any others and the only size they seem to sell is that $70 bucket. I just don’t need that much salt
@@yevad99 Thanks for the explanation yevad99. I've never had any experience with this process. 👍
What do anybody prefer for a ak bcg?🤔🧐
I can’t find any other brands than the one you showed ,all that seems to pop up is gun blueing supplies. Does anyone know of any other brands that sell in a smaller quantity.
stump remover
Which tape would you suggest for keeping freshly polished blades safe, while finishing the rest? (Green, blue, duct/gaffa) I want to buy one good roll, rather than adding another rubbish or to the collection 🙄
I think in a previous video of his I saw him use the purple 3M tape, apparently it has a plastic like layer, I'm also pretty sure the biggest trick is as applying multiple layers but the best advice would probably be to try and finish everything close to the blade before assembly as any abrasive will wear trough any tape. You know the old prevention is better than cure.
Don't really matter unless you're looking to expose parts of your knife to liquids afterwards in which case there's water/solvent resistant vinyl tapes for that kinda stuff. I for one use plain old painters tape. If I'm gonna clamp the blade thick layers of duct tape on top of that. The trick I suppose is to use tape instead of not using it and using something that comes off easily/doesn't leave a lot of residue so you for one: don't loathe using it and two: don't have to scrub away or use aggressive cleaning agents in order to clean your blade potentially ruining your finish that way.
Brownells has been out of these bluing salts forever now. Everytime they get back in stock i can't seem to get my hands on any. This must be a product made by a manufacturer and sold by several other suppliers. Can anyone chime back in and let me know of any places to look? I am out and desperately need to buy some for my business. Brownells has no clue when they will be back in stock and won't even discuss it.
Anyone's help is much appreciated.
So does this finish prevent rusting?
Yes, but they're easy to scratch
When you want to watch a new episode in bed but your wife is sleeping, guess we're reading captions.
What is a very durable finish?
Not much
So can I use Prague powder #2 for bluing?
I'm gonna experiment with a brand of stump remover I've got with a high purity of KNO3. Nothing valuable until I know how it behaves
What about using the salts as the temper?
I don’t think that’d be a good idea ,going off what he did for the blue color you don’t leave in long enough to get a good temper that would go all the way through your piece, also 600 degrees is going to leave you with a pretty soft temper. It’d be way to soft for any sort of small tool and would probably only suit some kind of axe or chopper. But even then it would be softer than my preference and the problem of the heat not going all the way through would become even more prevalent on those big and thick pieces.
Da Nuke There’s a company that does it, but they don’t go into details as you might imagine. I’ve still very new and this is still a bit above my current skills, but was hoping to get some knowledge saved away for later. Theoretically the higher the temp the less time to temper correct? Is the color change with the salts the same as temper colors? Or do the salts force the color much earlier than a usual heat temper? Could you do a longer (relative to the normal for just the blueing) soak at the lower temperature to temper the blade and still end up in the blue colors? At what temp do the salts liquify? If it’s used on gun barrels I’d assume it has to maintain a good bit of hardness.
Isheian 1: in theory maybe but your surface will still be tempered softer than your center material, and unless you take into consideration the heat conductivity of your specific alloy as well as closely monitoring the time you leave it in and the temperature of the salts you may be able to leave a tempered center in your knife. But this all seems way to elaborate to be worth it to me. 2:the color change from the salts doesn’t appear to be the same, the color change is from the thickness of the oxide layer on the surface of the steel and since in one case the steel is in open air free to react with oxygen while in the other case their submerged in melted salt it probably won’t be smart to base any tempering of the colors the steel gets. 3: according to the video you want a temperature of over 600 degrees for a blue color so I do not think you can get the blue color and have the salt at a temperature low enough to temper your steel. You may be able to temper a chopper with it at a lower temper and still get a straw color but it seems that the amount of time you leave the piece in for effects the color so you could end up with something past blue. 4: I don’t know the melting point 5: I do not know what the hardness of different gun barrels are but depending on what they need the lower hardness could be fine for them or a alloy could be used that has the properties they want. This all said their could be a alloy that would reach a good hardness at the same temperature as the salt I don’t know
Isheian if you want to experiment with it be my guest but if your looking for a way to color a blade I’d look into cold blueing or anodizing (I believe) these don’t damage your temper and they may better suit what your looking for
You sound like Scootch00.
That pyrometer...found under a pyramid?? Borrowed from Edison?
Something about this makes me scared. And I am not a safety freak.
Risk vs Reward!!!
can I do this on chrome polished bass and guitar parts ?
can chu make other colors such as say reds or greens or such 🤔
Can you please give us the temperatures in C too?
Amen a drop of Sweat will ruin your day.
Don´t use WD40 this is not to oil parts is to penetrate rust. WD40 is general is pretty crappy stuff, never use it as alubrication.