highly polished parts, and browning

[Jim Curlee]

I know on the guns that I've done, that the browning solution takes a better "bite" if the metals surface are a bit rough.

I have polished a lock, there's a pic, under my lock identification post.
I plan on polishing it a bit more, I think that's done with 400 grit.
Would you guy's leave the rifle in the "white" or would you try to brown?
I'm thinkin it will get a mottled appearance, but I don't have a clue.

Thanks
Jim

[L. Akers]

I have built guns that were polished bright to 800 grit then polished with tripoli polish on a muslin wheel.  I dilute commercial solutions up to 10 to 1 with distilled water.  I have never had trouble getting a part to rust and the end products are colored uniformly.  My process takes weeks--not days to complete.

[Long John]

Jim,

I have had similar experience to Mr. Akers.  I think the idea that a browning solution needs a coarse surface to get a "bite" in the metal is flawed.  The mean diameter of the molecules that actually react with the iron are on the order of  a million times smaller than the scratches left by 400 grit abrasive.  If you look at original French guns of the mid-18th century you will see guns with browned finishes that are as smooth as glass.  Some are a deep bitter chocolate color and others are a deep burgundy red.  If you want a fine, glassy finish then your browning must be done SLOWLY with short cycles using dilute reagent and the carding must be with a very fine abrasive.  Powdered rotten-stone in vinegar worked for me.  But getting a glassy brown finish takes lot's of time.  If a gun-maker is rushing to finish a job then a rough surface and long application times will give a very dull brown.  But it's brown and that's what the customer ordered.

That's all I know.

JMC

[Jim Curlee]

Interesting , the wife uses vinegar to take rust off of old metal.
I do know if you don't neutralize the vinegar that the rust will come back mighty quick.

So are you carding then neutralizing after each application of the vinegar solution?
Do you use oil at any time during the process?
How much rust do you allow before carding?

Thanks
Jim

[jerrywh]

I have polished barrels to 2000 grit and then browned them.  However it is a slow process.

[Long John]

Jim,

The vinegar in the mixture of rotten-stone and vinegar is to make the rotten-stone a slurry that can be pushed around with a cloth pad.  It is not intended to contribute to the rusting process as it is not left on the gun part like the browning solution is.  But in chemistry we are taught that like dissolves like.  Meaning that if you want to dissolve the product of an acid use an acidic solvent.  vinegar is a solution of acetic acid, a mild acid compared to the nitric acid in the browning solution.

Browning is a process where the iron substrate is covered with a layer of iron oxide - a mixture of ferric oxide and ferrosoferic oxide.  If you use a strong reagent and long application times the reagent will form pits in the surface of the steel.  The pit will be filled with iron oxides.  Under a microscope the pits will look like freckles.  The repetitive application of reagent causes more and more freckles to form until they cover the entire surface of the steel with freckles and any area between freckles is filled with another freckle.  This makes an inherently rough surface if the pits are deep.  Deep pits come from long application times.  Deep pits are facilitated with a rough beginning surface.  If you polish to 200 grit and apply your first dose or reagent, after a few hours microscopic inspection will show you a sting of roughly elongated pits along each scratch.  If you use a mild reagent, on a finely polished surface, with short application times, followed by a very fine abrasive you can achieve a glassy brown finish.  It is a time-consuming, laborious process but can yield beautiful results.

That's all I know.

Best Regards,

JMC
John Cholin

[smart dog]

Hi,
Here is an example of a highly polished barrel that was browned and highly polished lock that was charcoal blued.

[jerrywh]