I have had mixed results in the past with rust bluing. I've(I think) traced my past issues down to lack of humidity and too much realitive humidity.  In the past my rust never got rich red, more golden.  Or it got a nice red color but water drops were on my parts and made the finish splotchy. 
So... I have built a humidity cabinet to try and control my environment and have repeatable and predictable results.   
I'm testing the process and I'm curious what tempature and humidity levels others found ideal in their damp boxes.

try mark lee's #1, i was told about it by joe ruth an old time gunsmith ,collector and restorer. he had a sweat box he used for years, when he found this he never went back.  it is easy and all you need is a boiling tank.  brownell's sell's it.  i have 3 i've gotta do soon.   tony<><

I did my second barrel with Mark Lee’s today. Learned a few things on the first one, a junker. I couldn’t be happier with the results….a beautiful blue/black luster after (5) application cycles. Doing the 3rd of (7) tomorrow morning then the rest of the day will be moving snow to more appropriate places.

My friend Al Springer does some of the finest rust bluing I've ever seen and he told me he wrings out his cotton balls after wetting them in solution until they're only damp. Then he makes a pass down the barrel and tosses the cotton ball, and grabs another to go forward. This eliminates streaking you get from applying solution too wet.
Al sent me a video he did years ago when he was selling his homemade rust bluing and it was very interesting, and made me change how I do barrels. I still do my own if it's just a barrel, but if I need color case also I let al do it all.
I also use Mark Lee Express bluing and I find it's tough for me to mess up using it. It's very forgiving.

Mark Lee's Express #1 Rust Blue and #2 Rust Brown 
are the same formula,,just different ratio /w water soln %.
I forget which is the weaker one. 

But both work the same way in that they rust the metal immeriately by warming the surface and then applying it. 

Then right into the boiling water tank or now many use a steam set up.
This is made with Potassium Chlorate & Iron Nitrate as the primary rusting chemicals.
Old solns for Express Bluing/Browning are the ones that often had Mercury Bichloride in them
(Herter's Belgian Blue was a very popular one. 'Bakers Formula' another. They all were applied the same way.)

Potassium Chlorate will certainly do the job though w/o the dangers of Merc left behind in the carding dust around the shop and home. It's a HD oxidizer all by itself.

Mark Lee's #3 is a Slow Rust formula.
I do not know what they use for it. 
Laurel Mtn is a Slow Rust soln and it has Ferric Nitrate (Iron Nitrate) in it. A little Nitric acid and Copper Sulfate.

Slow rust needs time to for the parts to rust. A couple hrs to a day depending on the temp/humidity,etc. Applied to room temp parts. No warming of the parts for application.

Lots of people starting out get confused when Rust Bluing is mentioned and the type of method is not.
The techniques are different for application as are the formulas needed for each.

I do both and have for about 50yrs or more.
LaurelMtn for Slow Rust and Mark Lees #1 for Express.
Both have available in them the ability to produce slightly different characteristics. 
Both will produce a ''blued finish'. Many times that criteria is all that is needed and is good enough.

But often one or the other can be chosen & used along with careful polishing and different application techniques to produce a finish and final look needed for a specific project. Restoration work done right requires it.

Hebes405 wrote on Feb 9^th, 2025 at 9:14pm:


My local hardware store still has them.  Still cheaper than fluorescent or LED if you ignore how long they last.

I would get Water Drops on my Barrels almost as soon as I would place them in my Damp Box.  Figured out that a Cold Barrel into a Warm Space was the cause.  So now I take a Heat Gun and warm the barrel before hand.  -12 on our walk this morning 😯  David

Thanks everyone for the input. I finished my cabinet today. I call it the bivins box mk3. 
A local gunsmith gave me an article written by bivins in the 70s about metal refinishing. I copied his design and made a few upgrades. I totally went over kill. I added automated heat/ humidity controls and a circulation fan, per the recommendation of my gunsmith pal. 
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