nitre blue - nitre substitute

[mattybock]

I was having a looky-see at the different methods of bluing and was wondering what is the simple prettiest method. I say Nitre bluing. I love that purplish-blue that you can get.
And while reading how to actually do it, I found out that the Nitre is more or less a heat transfer agent, and the process is very akin to flame bluing. With the Saltpeter brine at 610 degrees or so, the blue takes on that pretty color. And I go to wondering something-

Is there an actual chemical change taking place that only saltpeter can provide, or is it possible to use another (less kaboom-y) brining agent to get similar results, like plain table salt, or something like it?

 

[Black Hand]

Why would you think that potassium nitrate is explosive? http://en.wikipedia.org/wiki/Potassium_nitrate_(data_page) http://www.sciencelab.com/msds.php?msdsId=9927232

 

[mattybock]

i thought it was because it's the main thing in black powder.

 

[dcriner]

Potassium nitrate is an oxidizing agent. So is oxygen itself. Both are harmless by themselves.

 

[rusty]

the best cold blue is oxpho blue,from Brownells,it is available at many gun stores

 

[Black Hand]

i thought it was because it's the main thing in black powder.

In combination with sulfur and charcoal, yes.
By itself, no.

 

[jdkerstetter]

Hey Rusty, Oxpho is pretty good stuff but the 44/40 is better....if you haven't tried it. Pricier, but better.

Neither is as good as the hot tank bluing that Matty is referring to. Hot tank requires more equipment and is more problematic though.

Enjoy, J.D.

 

[M. De Land]

Yup and hot tank bluing can't hold a candle to cold rust bluing for color or durability.
I have to say I grew to dislike hot acid bluing after 30 years of using it. Still have my tanks and equipment but once I learned to Niedner rust blue I never have cared for hot tank bluing any more. It is faster and better suited for production but there is no comparison of quality between the two, properly done. Mike D.

 

[GaCop]

+1, been using it for years. Best results require heating the part.

Tom

 

[blackdog of vt]

No, It just tranfers the heat just like fire blue but easier to evenly heat a part. Table salt doesnt work. Its not rust resistant and the color changes over time but it is pc and pretty to look at when used on a small parts on a rust blued gun. Those two are how I finish almost all my guns and all my personal ones. Rust blue is easily made from vinegar and peroxide. No cold or salt blue can hold a candle to either.

 

[crockett]

Tell more details on the peroxide and vinegar blue solution. Know nothing about it.

 

[mattybock]

So that pretty purplish-blue from the nitre method will eventually fade? What color would it fade to?

 

[blackdog of vt]

Mix 50/50 paint on heated steel just like rust blue solution, it will rust, then boil. Really its just the same as rust blue directions from the mass produced stuff.
It gets more gray over time but still retains color

 

[blackdog of vt]

More gray meaning the nitre blue not the rust blue.

 

[mudd turtle]

Ok Jake ! I mixed 1/2 vinager&1/2 poroxide togeather and nothing happened. I heated the metal ! Where did I go wrong? Mudd Turtle.

 

[blackdog of vt]

If its not aggresive enough add more peroxide and 2 tspn of salt per 2oz of vinegar. The metal should be hot enough to evaporate it almost right away. 20 minutes to rust is plenty before boiling. It will take 10-15 coats to get a deep even blue. If still no results with instant rusting your peroxide may be old.

 

[M. De Land]

I have the formula for Nieders rust bluing. Mine will blacken a barrel the first pass without any acid etching. It does it's own etching as it consists of nitric and hydrochloric acid in distilled water with dissolved black wire added.
Each pass spends 3 hours in a rust cabinet supplied with humidity and heat. Six passes is about maximum as the solution will begin to make the metal surface pitted like LMF does. The boiling turns the oxides brown/black. I've never seen a blue that can come close to it's durability over wear and time. Mike D.

 

[blackdog of vt]

Mine wont pit the steel, is a very atractive blue, tougher than you may think, and is perfectly safe.

 

[GaCop]

I love this site. I learn more and more every time I come here! :thumbsup: :hatsoff:

Tom

 

[Rifleman1776]

the best cold blue is oxpho blue,from Brownells,it is available at many gun stores

I have used it for many years as a touch up. It is not durable and should not be considered permanent.