rust blue/gun blue questions!

[Keganthewhale]

so from what i've gathered to rust blue something you must clean the surface from any coatings, oiled, other finishes, then you must allow it to rust a deep red, thick and thoroughly, then you must 'boil' it in distilled water and then essentially rub/polish it down with a cloth until it turns a blackish color.

now if there is more to it than that i am all ears! (i figure it wont be terribly easy to do, but those are the steps i've come to understand)

now my question here is this, i want to blue a certain part of mild steel but not another section of the same piece.

so lets say we have a 6"x6"x1/4" piece of mild steel that has had its surface cleaned by heating it to a cherry red and hit with a degreased wire wheel until cool, then cleaned with acetone.

 

how can i get a 1" stripe of blue down the center yet keep either side  essentially polished or at least rust/blue free?

[DSW]

I've never done it that way, but then I've only blued a few pieces with a friend years ago who was into gunsmithing. This Brownells link pretty much explains how we did it. Brownells is usually fairly helpful as far as giving out info on their products as many are often geared towards "hobby" gunsmiths. You might give then a call and see how they'd suggest masking off an area that you don't want blued. I'm betting they know how or can make some suggestions.

 

http://www.brownells.com/aspx/learn/learndetail.aspx?lid=11044

[tantofolder]

In my opinion most blueing looks better on polished metal. There are many brands of cold blueing and they all seem a little different in their final look(depending on prep,application,etc.).You can also get a great blue(s) just with heat.I have done this in a standard oven....though I can't recall the exact temperature(s) off the top of my head.If I were to try this myself,I would wire brush as you described,then heat to the blue I wanted. Finally,I would mask the blue that I wanted to keep and wire brush again to remove the blueing in areas I did not want blue.I think the same could be done with cold blueing as well,but it may be a bit tougher than the heat blue to remove.

[Keganthewhale]

my final result, if i can find a way to get it to work without rusting the whole thing then removing what i don't want there, is to essentially draw a picture whether it be with wax or oil or something then let everything else rust and blue, basically leaving you a negative blued picture on a steel plate.

but i'm more interested in the process than the end result, because i absolutely could rust blue the whole thing and go back with a dremel and remove the blue i don't want.

does that make sense? because sometimes i think my ideas are crazy because i've never seen them done before.

[Rich Hale]

The method you asked about is not the normal way. Most bluing or browning formulas involve some salts. The only way to figure this out is to simply try it. First as you describe and then either mask off the areas you do not want done. Or try your way and remove areas you wish clean. 

[tantofolder]

Perhaps you could do an acid or saltwater etch to define your different areas? Then you could come back and treat the different areas as you want them.

[BIGGUNDOCTOR]

For that application I would get some Oxpho cold blue. Warming the metal with a heat gun will help the blue work its magic better. We would sand the surfaces down to a 320 finish then hot blue with Brownell's salts. For touch ups, or small parts we used the Oxpho on warmed parts. When using the Oxpho you Need to keep the surface wet till the desired color is achieved. You could have that part done in a few minutes, not hours.

Your process needs a humidity cabinet, one of many bluing formulas, wire brush,and time. Once you start you have to carry it out till the end results. You also do not want the rust to get to the red stage, only dark before carding it off with the wire brush. The process of wiping with the solution, hanging in the humidity cabinet, carding , and repeating can intake upwards of 8 hours.

We found with sanding the blue bit into the surface better than with a polished surface, especially a buffer polished surface, as the buffer smeared the surface which closed the metal pores.

Good luck on the project, lots of info out there on the net.

[striker9]

hello, if you are still needing info on rust blue process pm or email me and I can send you lots of stuff.  I'm a gunsmith, have performed rust blue restorations or on new build firearms many times.  I have my own recipes, I don't use the off the shelf stuff you pay an arm and a leg for.  that said, there's nothing wrong with the brownells products or those they sell, I just won't pay $36 for a 6oz bottle when with the chemistry background we all posses can make our own formulas.  it will all come down to experience however.  the more you do it, the better you'll become at it.  also, the more you play with various chemicals (salts) the more familiar you'll become with results and expectation from a particular formula.  i'll add as a precaution that without a chemistry background, or at the very least, ability to research extensively the chemicals you are using, how to mix, what to mix, what NOT to mix, then I would stick with off the shelf stuff.  anyways, if you want info ping me and i'll be happy to scan and send.  too much to post in a tread.  it'll make your head pop!