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Leif S

Blackened and antiqued hardware!

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I have been experimenting with a durable rust finish for sword hardware for some time now (years actually) and have come up with a fast rust finish that is durable and *black* which was what I was after.

 

yachoblack.jpg

 

It's nothing new really, just a twist on the way guys used to blue/blacken firearms by rusting, carding, and then boiling. I used hydrogen peroxide, salt, and vinegar to flash rust the surface for multiple cycles and then boiled the fittings in distilled water for 10 minutes. The fittings were covered in Ren. wax while still hot.

 

My question is: What chemically happens to the red rust when it's boiled to make such a deep black color? It just amazes me how durable this finish seems to be (we all know how hard it is to get rust off of clean steel surfaces!) but my wife asked me why does the red turn black and I simply don't know. [dunno]

 

Any chemists out there?

 

Brian

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I cant answer your question, but I have one for you. Do you kill the vinegar solution on the peice with baking soda between dips? This is very new to me and I can see that I could use this technique. Is you hardware mild steel or does it apply to carbon as well? Are you willing to give the mixing ratio of the parts? From the pictures , I see that it works great and would appreciate more info. Lin Rhea

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I can't answer either, however I was also wondering if you were willing to give out the ratio of the mixture?

 

I have heard of people heating the piece up and rubbing it with linseed oil to get a black finish but it doesn’t look nearly as good as yours.  Your process also creates a very unique texture.  Very nice.

 

Daniel L. McDougall

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I will third the motion. Any details on your process would be wonderfull. It tis business and beautifull at the same time.

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The mixture is simple. I use approx. 1/2 cup of regular Walmart hydrogen peroxide and warm it up in the microwave....don't boil it, just steamy. Then put it in a glass container with a screw on lid (a mason jar) and add table salt a bit at a time until it is saturated. Add a little, shake it up, add a little more til no more will dissolve. Then add about a couple of capfulls of white vinegar...say maybe an ounce.

 

I warm it back up and put it in a little spray bottle. Use very clean steel and spray it all over the piece. It will foam and steam and you will immediately see red rust in the foam. Spray it again and keep it wet for maybe 30 seconds. then just stand there and let it complete it's reaction...it will stop foaming. Rinse under hot tap water, don't rub the piece just rinse it.

 

Then while it's still hot spray 'er again. Repeat the spray and rinse routine for about 6 or 7 cycles and the steel will have a thick, uniform coating of fine red brown rust. Rinse it and then boil it in distilled water for 10 minutes until it turns jet black...Remove from the boiling and coat with Rennaisance Wax. It's done and beautiful.

 

yachoglossyfuchi.jpg

 

The texture on the tsuba (the tsuba and kashira in my first pix) was actually pre existing due to other botched attempts at producing the right results. But I like the antique look so it stayed. The fuchi/collar was done with a very clean and etched surface and it came out glossy and without any pitting or antiquing at all. It actually shines in direct light. I will continue experimenting with textures but the finish is *very* tough...like rust. I love it.

 

Like the pix above! See the shine?

 

soooo...

 

Why does the red rust turn black? And remember, don't hide how it's done if it works for you. Pass it along to others who need the help or can use the process.

 

Brian

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Great tip Brian, I am going to try that next time out. Good question on the color shift, I am sure someone out there is up on their chemistry and will fill us in. Thanks. [applause]

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A bit of brief research hasn't produced anything in my books about colors changing.  The gun folks have used boiling water for years to change the gun barrel colors from brown to blue or black.  I wonder if it isn't a heat/oxygen change.  

 

However, the last time I acquired iron (94% powder and 96% sintered nuggets) from the mine, it was black.  The powder was a dead black, the nuggets more black gray.  Exposed to the atmosphere/humidity they both turn red.

 

Both of those forms are listed as iron oxide.  There are two molecular forms.  Ferric oxide and Ferrous oxide that would be simplified to plain iron oxide.  I'm still checking on the colors of both types though.  Chemistry books aren't that complete.  

 

Any artist types out there who work with iron as a pigment?  They might have a better answer.

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In the mineral world ferric minerals are normally rust colored,some darker than others (up to dark chocolate), and ferrous minerals normally gray-green to gray-greenish black. Both can sometimes appear totally black.

 

Rust is ferric hydroxide, Fe(OH)3, a result of oxidicing massive iron. Ferrous iron is a result of reduction.

 

The reason this mix of yours reacts so fast is that the H-peroxide reacts with the vinegar to create a weak base that oxidices the iron. This reaction also produces water, which speeds up the rusting process.

 

Now comes the tricky bit, why does it turns black? It could be as simple as that boiling reduces ferric iron into ferrous iron. It could also be that the boiling turns the hydroxides into oxides with a little denser stucture which make them appear black. It could even be both.

 

Tell me, if you don't coat with ren wax does your pieces rust?

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Stuff that's browned or browned and blackened can develop rust occasionally, if not oiled and waxed, but it's like a bleed-out effect... a little oil and light rub with steel wool and it blends right into the finish and dissapears.  Browning has been one of my favorite finishes since I was a kid... even do it on blades occasionally, takes care of the "I hate stainless" issues  :0)

 

I was using brownells "Plumb brown" for awhile but ended up going back to old-timey recipe's like Brians', they make a deeper and nicer coloured finish in the end.

 

To add to brian's routine, if you heat the piece being browned as well, 200f or so , while you are applying, not only does it make an incredible mess in the workspace that never ever cleans up totally, but it gives you intermediate shades between the tradtional reddish and the boiled black oxide... it's a deep chocolate brown with hints of a purple undertone sometimes, similar to the colour you see on antique Japanese ironwork occasionally.

Spray it on and keep spraying coats untill the piece is cooled and isn't steaming off the mix anymore, then re-heat and re-apply.

 

After this, if you boil it, it'll turn black but still seems to have a different undertone of colour, at least to me.

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This sounds like the perfect finish for a tsuba I'm close to finishing!

 

I've been fiddling a bit with rust finishes but I can't get them to turn black by boiling.  [wtf]

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If I remember correctly Red Iron Oxide is Fe2O3 while Black Iron Oxide is Fe3O4.  This info is from pottery supply catalogs where both compounds are sold.  I would imagine, (educated guess here) that the boiling converts the Fe2o3 to Fe3o4.

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Guy, this was the part that took me years to get right. I used to rust the stuff for days with all kinds of crazy concoctions (like the peroxide and salt ain't a concoction ??? ) but it all just came together when I flash rusted and boiled. The whole #### thing takes about 20 minutes if you do it the way I described above.

 

Thanks for the explainations from Mike and Leif...I guess if it works who really cares how or why. [dunno]  Still, I sometimes wish for more technical education.

 

Randal, the variations as you stated are also *very* nice. the purpleish browns are very classy as well...I ran into those colors along the way. I hope to be able to produce multicolor fittings this way eventually but have a few projects that will delay that experiment for a while yet.

 

I have not seen any rust form after finishing....but it has not been that long and the wax is sure to stop that from happening as it was applied while the steel was yet very warm. It is virtually encased in wax but I will do an oiled version next.

 

Good stuff, Dudes. It's magic. Me like.  [ylsuper]

 

Brian

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For a really nice deep black smooth finish try a nitrate finish. Some of the old German firearms used it.

 

Ken

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Just to share a rather botched experiment, I found an ancient recipe that was supposed to yield a nice blue-black finish on steel. You were supposed to mix sulphur into pure turpentine heated over an alcohol lamp and apply this mixture to the steel and heat with the lamp. Well on my first attempt I flashed the turpentine sulphur mixture wich made the most god awful stink and then couldn't get the sulphur (flowers of sulphur from the drug store) to mix into the artists quality turpentine but tried to coat the steel with it anyway. Boy what a mess that made! Needless to say I didn't get any kind of finish I'd want to show anyone! And I had to get several showers before I got rid of the burning sulphur smell from my hair and skin! I will definitly be trying this quick rust recipe soon! :D

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For a really nice deep black smooth finish try a nitrate finish. Some of the old German firearms used it.

 

Ken

Hey Ken, can you describe how the nitrate finish is done? What stuff do we need and how is it applied? I'm always lookin' for another way.

 

Thanks!

 

Brian

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Hi Brian  ..  quick, easy and cheap.  Solution is -  5 lbs. lye (sodium hydroxide), 2.5 lbs. ammoniun nitrate ( fertilizer) and 1 gal. water.   I reduced amts. to get 1 qt.   Lye you can get at the grocery store and AN at the feed store.  Working temp. is 290*f + or - 5*.   Make sure to use plenty of ventilation as the AN gases a lot.  Also don't use an  aluminum container 'cause it will disappear when you add the lye (I used a ss bowl and propane burner).  Apparently the lye is used only to raise the boiling point of the solution.  Clean and degrease work piece then place in solution for 15 - 40 min depending on metal used.  When done rinse in water, dry and oil.  I've used this once - very pleased.  Roy Dunlap's book - Gunsmithing has several blueing/blacking/browning formulas in it.

Ken

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I like the quick and easy home brew nitrate formulae, but it sounds an awful lot like the low temperature gun bluing solutions.  The temperature is pretty much exactly what the commercial solutions recommend.  The nitrate gun blues would be a viable alternative.  Some of those come out nearly black.  The home recipe is good, no hazmat shipping fee.  

 

There has been some confusion over the term "hot blue."  What I think of hot bluing is running low temperature salts, sodium and potassium nitrates up to about 600-700 degrees F.  

 

More commonly it seems that hot bluing refers to the chemical baths in the 290 degree F range.

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Cast iron skillets are nice and shiney to start and then, as they season for a while, turn black. It has to come from the oil used on them to season it. Just like the oil used on that tsuba.

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I was doing some investigation into the chemistry involved and ran across a reference to the following chemical equation:

 

Fe + 4Fe2O3 = 3Fe3O4

 

So since Fe2O3 is hematite or red iron oxide and Fe3O4 is magnetite or black iron oxide it seems plausable that the application of heat in the proper environment would allow the Fe2O3 to react with the Fe (iron) while preventing the iron from reacting with any oxygen.  Hence the red rust is converted to black.  I'm not a chemist and I don't currently have any chemist friends to verify this either but what I do remember of college chem classes seems to support the above.

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Fe + 4Fe2O3 = 3Fe3O4

 

So since Fe2O3 is hematite or red iron oxide and Fe3O4 is magnetite or black iron oxide it seems plausable that the application of heat in the proper environment would allow the Fe2O3 to react with the Fe (iron) while preventing the iron from reacting with any oxygen.  Hence the red rust is converted to black.  

Dude! I'll just bet you have nailed it! But the wife has moved on to more questions and she probably doesn't care why it turned black now...but I'm still curious and I *really* appreciate your input.  [notworthy]

 

I have tried the commercial bluing/blackening routines...not the nitrate finish Ken was describing but lots of others. This rust finish with the boiling is *way* cooler than any of the other chemical or bluing type stuff I have used before. I have been using heat coloring in molten salt for some years but this flash rust and boil routine works better and is *a lot* more durable than the heat oxide coloring....as long as you like black. :cool: ...which I do!

 

This has worked out so well that I am actually back tracking and unfinishing several finished fachi/kashira/tsuba sets I have on hand to refinish them with the black rust finish.

 

Commercial cold bluing solutions work very well if you boil them to make them black as well and are cheap and easy to apply...but the boiled rust is still denser, blacker, and more durable. The only black finish I have found that is more abrasion resistant than the rust black has been lacquer or paint. Which looks surprisingly good if done well. Black baking lacquer (Brownells) *rOcKs* if you opt for a finish of that type.

 

The natural, easy, non toxic, no fumes, approach to the rust black is really appealing to me as well. I have devoted almost 5 years to getting the rust black to perform and look the way I envision steel fittings to be. My advice is to try it once or twice if your in the market for this kind of thing. It's way too easy and cool.

 

 

Brian

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Robert , the book I got the formula out of says the solution is good for 35 - 50 blacking jobs.  Apparently the AN stays in the tank and only the lye and water boils out.  It also says to add a pound of lye every 12 -15 jobs (remember this is based on the full mixture) and water as necessary.  I know from experence if you get the temp too high the solution will boil away fairly quickly.  Also as to Brain's concern about a durable finish this finish is supposed to take a wire brush test without any damage (I don't know - ain't gona try it on my tsuba).

 

Ken

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I use a cold blue on my damascus.  You apply and then buff the high spots down, leaving the blue in the hollows.  Do you suppose this process would work for that kind of application?

 

Geoff

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I used to be a chemist...so here's what I have been able to find out.

Rusting starts with iron losing 2 electrons to oxygen to form iron 2+ ions. Iron 2+ and oxygen 2- combine to form iron (II) oxide FeO which is black. The electrons react with water to form OH- ions, which also react further to make iron (III) oxide Fe2O3 which is red (hematite). To make it even more complicated, there is also iron (II,III) oxide Fe3O4 (magnetite)which is a combination of the first two. Rust is a combination of these with extra OH- attached in varying quantities, which also is what limonite (bog iron), goethite, and other iron-bearing minerals are made of.

 

So, by manipulating the levels of oxygen, H+ (acid) and OH- (base) you can drive the reaction to favor one form or another of iron oxide. The peroxide adds oxygen ions, while salt and vinegar together make a variation of hydrochloric acid (also called muriatic acid, HCl) that adds lots of H+ and Cl- ions to the mix. All that together makes really quick rust. As someone else mentioned, the boiling keeps oxygen away from the surface and the heat promotes the change from red to black oxide. Black oxidation/rust is also characteristically formed in buried or underwater environments that lack oxygen, preserving Viking swords for our enjoyment.

 

All in all a cool process! thanks for sharing it.

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