Bluing / Blackening of steel

[Alveprins]

Hi guys,

 

I've seen some really black knife fittings lately, and I am curious as to the process of getting them that way.

From what I could see in the YouTube video, the bladesmith lowers the parts into a thick boiling "goo" and leaves it for an unknown amount of time. When the fittings come back out, they're pretty much jet-black! 

Link: 

 

He talks about "bluing salts" at some point, perhaps in another video.. I don't remember.

 

Anyone able to explain the ingredients of this "goop"?

 

Sincerely,

Alveprins.

 

[Brian Myers]

Bluing salts are used a lot in the gun industry. They create an oxide layer on the metal that helps protect it. The ingredients are usually potassium and sodium nitrates.

Edited January 31, 2021 by Brian Myers

[Alveprins]

Seems I found a recipe on this very Forum: 

Problem is - I can only get the Sodium Hydroxide for this mixture, I cannot get the Sodium Nitrate.. absolutely unavailable in my country, and by the looks of it - Europe.

All plant fertilizer is "non toxic" etc. containing not the faintest trace of Sodium Nitrate.

 

 

[Gerald Boggs]

I've no experience in this area, but what about room temperature blacking, like Birchwood's Presto Black or Caswell's Black Oxide Kit?

https://www.birchwoodtechnologies.com/products/black-oxide/steel/room-temperature/

https://caswellplating.com/black-oxide-kit-1-25-gal.html

[Brian Myers]

Also look at Brownells. I think they ship overseas to Europe and buying something premade gives you the assurance that it's premixed just right and ready to go.

[Alveprins]

33 minutes ago, Brian Myers said:

Also look at Brownells. I think they ship overseas to Europe and buying something premade gives you the assurance that it's premixed just right and ready to go.

 

I tried accessing the "Brownells Nitre Blue Blueing Salts product page - and was immediately re-directed to a page with European dealers - which of course don't have it.

I had to connect using a VPN masking my IP as being from New York in order to view it.

 

I am going to make a phonecall though - to the Norwegian dealer of Brownell's products tomorrow. I see they sell blueing tanks and thermometers and such - just no chemicals - which seems a bit useless.

 

I'll let you guys know how it goes - if it is of any interest.  Everything is so difficult here in Norway. No access to anything that could be slightly dangerous - in terms of chemicals and other useful things.  Nanny-state. 

[Brian Myers]

If your local or government laws are too strict on gun-related items, then try what's called rust bluing. It's a drawn out process, but the layer of oxide that builds up is fairly thick. All you really need is some type of mild acid, a damp box and a carding wheel. It's a process that is repeated over and over till you're satisfied with the layer of oxide. Go to YouTube and look up MidwayUSA. They actually have a fairly decent video on the process.

[Alan Longmire]

Rust bluing is nice, but it doesn't give you the deep dark shine of hot blue.  You can get the sodium hydroxide?  You can make your own potassium nitrate if you want.  Or check sausage-making suppliers.  Curing salt is often sodium nitrate...  The potassium nitrate works just as well, but is not pleasant to make.  Google "making saltpeter."    

[Alveprins]

18 minutes ago, Alan Longmire said:

Rust bluing is nice, but it doesn't give you the deep dark shine of hot blue.  You can get the sodium hydroxide?  You can make your own potassium nitrate if you want.  Or check sausage-making suppliers.  Curing salt is often sodium nitrate...  The potassium nitrate works just as well, but is not pleasant to make.  Google "making saltpeter."    

Thanks man!

 

Actually, I don't really have time to collect my own p*ss for months, so I will have to try to get potassium nitrate somehow if it can function as a replacement for sodium nitrate.

 

I see the farmacy here in Norway sells it, but at the quantity I need (2,5 pounds) I'll need to fork up 500 USD. 

[Alveprins]

I believe I might have a solution...

 

I can get my hands on Lye ( NaOH) Sodium Hydroxide in the form of good old "Caustic Soda" which is is sold for cleaning.

As for the Potassium Nitrate (KNO3) or Sodium Nitrate (NaNO3) - I can get some Calcium Nitrate Fertilizer containing  more than or equal to 90% Nitric Acid (HNO3) - while the rest of the fertilizer ingredients are Calcium Ammonium Nitrate (CAN for short) (5Ca(NO₃)₂•NH₄NO₃•10H₂O)

 

If I could possibly use 5 pounds of Lye (NaOH) and 2,5 pounds of Fertilizer (90% Nitric Acid HNO3 + 10% CAN) dissolved in 1 gallon of distilled water - that would be doable for me.

 

I worry about that added ingredient in the fertilizer though, the CAN containing ammonium nitrate.

The recipe says ammonium nitrate can be used if it is pure - but will create ammonia gas during heat-up. In this case, roughly 90% of the fertilizer will be Nitric Acid while the rest being Calcium Ammonium Nitrate.

 

I don't know if the CAN with create problems with the mixture in it's entirety?

And just how explosive would a mix like this be? I'd hate for it to blow up in my face... 

 

EDIT: Seems I found another fertilizer that is 100% Potassium Nitrate (KNO3) ... Might need a license to buy it though. Will have to check with my farmer friends.

 

Anyhow, going to call Brownell's Norway tomorrow and see if they have s solution for my bluing salts problem in general....  If they can help me out, I'll effectively avoid this whole sketchy experiment.... 

Edited January 31, 2021 by Alveprins
new info

[Alan Longmire]

With any bluing salt mix you will have enough nitrates to make things interesting. 

 

Be sure not to spill any on any cellulose-containing items, like wood, cotton cloth, paper, etc.  Nitrocellulose is a wee bit unstable. 

 

Also, the fumes will rust unprotected steel in the same room, so do it outdoors.

 

This is interesting chemistry, but it can also put you on any number of watch lists, even though what we are doing is harmless.  Be careful and keep it above board. 

[Alveprins]

UPDATE:

 

Alright, so seems I am able to get the salts.

 

I called up Brownell's Norway ,who directed me to a gunsmith, who again directed me to another gunsmith who imports the stuff. He has about 700kg (1500 pounds) in stock, so I will be droping by him real soon.

 

I will buy the tank itself from Brownell's, however the burners are way too expensive at 500USD for a complete burner. I suppose I will have to make one myself. Next thing is to get a long metal pipe, and some sort of regulator / air intake thingy....

[Brian Dougherty]

You might see if the gunsmith will be willing to blue your parts for you.  I get the desire for "sole artistry" as much as anybody, but there is a learning curve to blueing.  Having a specialist do a few sets of parts might be nice before you take the plunge on buying your own kit.

[Alveprins]

3 minutes ago, Brian Dougherty said:

You might see if the gunsmith will be willing to blue your parts for you.  I get the desire for "sole artistry" as much as anybody, but there is a learning curve to blueing.  Having a specialist do a few sets of parts might be nice before you take the plunge on buying your own kit.

I get you Brian, but my mind is dead set on this.  I need to have this equipment close and ready, and I will have to learn how to use it as it seems I am taking this bladesmithing business from hobby to full-time.

 

[Brian Dougherty]

In that case then, go man go !

 

[Brian Myers]

Of course, we have to say this. Be careful! You're going to be dealing with a pot of heated salt solution in the 400 to 600 degree range, well over 200 celsius. One splash and you have 3rd degree burns. So, face shield, respirator or well ventilated area, heavy leather apron and leather gloves. You can't use cloth because the liquid will soak right through them.

Edited February 2, 2021 by Brian Myers

[Charles dP]

22 hours ago, Alveprins said:

I believe I might have a solution...

 

I can get my hands on Lye ( NaOH) Sodium Hydroxide in the form of good old "Caustic Soda" which is is sold for cleaning.

As for the Potassium Nitrate (KNO3) or Sodium Nitrate (NaNO3) - I can get some Calcium Nitrate Fertilizer containing  more than or equal to 90% Nitric Acid (HNO3) - while the rest of the fertilizer ingredients are Calcium Ammonium Nitrate (CAN for short) (5Ca(NO₃)₂•NH₄NO₃•10H₂O)

 

If I could possibly use 5 pounds of Lye (NaOH) and 2,5 pounds of Fertilizer (90% Nitric Acid HNO3 + 10% CAN) dissolved in 1 gallon of distilled water - that would be doable for me.

 

I worry about that added ingredient in the fertilizer though, the CAN containing ammonium nitrate.

The recipe says ammonium nitrate can be used if it is pure - but will create ammonia gas during heat-up. In this case, roughly 90% of the fertilizer will be Nitric Acid while the rest being Calcium Ammonium Nitrate.

 

I don't know if the CAN with create problems with the mixture in it's entirety?

And just how explosive would a mix like this be? I'd hate for it to blow up in my face... 

 

EDIT: Seems I found another fertilizer that is 100% Potassium Nitrate (KNO3) ... Might need a license to buy it though. Will have to check with my farmer friends.

 

Anyhow, going to call Brownell's Norway tomorrow and see if they have s solution for my bluing salts problem in general....  If they can help me out, I'll effectively avoid this whole sketchy experiment.... 

 

My thoughts reading this were: you are so getting arrested  

[Alveprins]

11 hours ago, Charles dP said:

 

My thoughts reading this were: you are so getting arrested  

Haha! 

 

Nah, this is Norway - not the US.

 

Anyhow, seems I can get the real deal - and won't have to experiment.

[Doug Lester]

I have some experience in acid bluing fittings.  I exposed them to muratic acid fumes in a container to build up a layer of rust, brushed it back a bit with a steel brush, and repeated the acid fumes in a container until I was satisfied and then boiled the part in water.  The parts came out almost black; not like the gun blued parts in the picture.

 

I'm trying to remember, which is hard at my age, but I believe that someone made a solution of table salt in hydrogen peroxide to build up the rust on the fitting.  Of course if that fails you could just pee on it until you're satisfied with the depth of the rust.

 

Doug