hot blue solution

[woodchucker]

well, sodium hydroxide is drain cleaner so that should give a clue,
Sodium Nitrate is used as a preservative in bacon and hot dogs. Its also found in a lot of plant products especially spinich so again should not be a problem.
Mind you from what I gather it may be a different problem altogether in California.

Everything is a problem in California.. Air can cause cancer in California... At least that's what the warning label when you get off the plane says.

 

[gi_984]

https://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/metal-bluing/index.htm

Here (USA) Brownells is the major supplier for bluing supplies of all kinds. If you go to the above link check out the free articles. Lot of good info on bluing. Good folks. I've purchased a fair amount of stuff from them over the years.

For small periodic batches of bluing, Steve Acker has a good small scale bluing chapter in his "The Gunsmith Machinist". He uses it often to hot blue his machining projects in addition to gun parts. Can't remember if it is volume 1 or volume 2. I got mine thru the local Library. Liked it so much Santa is bringing both volumes for Christmas. I will be fabricating a small scale bluing tank based on his.
https://www.midwayusa.com/product/318226/the-gunsmith-machinist-book-two-book-by-steve-acker

 

[Silverbullet]

I made a three tank with home built burners with upper rods to suspend the parts . They don't want to touch any other metal in the solution . And they need to be boiled and dried before emulsion. The better your polishing and cleaning , the better your bluing or Browning . It takes several trips in the tank for the rust blue methods . Carding and cleaning then another dip. Been along time but I think that's the way.

 

[Crank]

savarin,
The best material for the tanks is black iron, I don't recall the specific reason, but stainless had some quirk that made it a less than ideal material. Wash tanks and rinse tanks pose no issue. I did a lot of bluing in the gunsmithing world and have two specific warnings beyond common sense safety practices.

1) Keep the bluing area completely detached from any precision equipment, the vapors will rust EVERYTHING!!!
2) Have a spray bottle filled with vinegar close at hand to spray your skin with if any of the solution gets on you. The vinegar will keep you from realizing too late that the soapy feeling is your skin getting perforated. Those little pinholes in your skin, hurt like the dickens afterwards.

Bluing is an amazing process, however it often feels like alchemy. I have seen steel go in the solution and blacken almost instantly and on other occasions it would sit unblemished for most of the cook time and then decide to turn in the last minute. The trick to making it work is temperature control, too cold and nothing happens, too hot and your salts are dead. Cleanliness will make your salts last an amazingly long time and don't inadvertantly put an aluminum part in the solution, it will turn into an Alka-Seltzer and cease to exist (killing the salts in the process). As others have stated, Brownells is a great resource for information.

Mark

 

[savarin]

Excellent information as usual guys, thanks all.