Brass alloys and copper green crud

No guarantee but dip the brass in hydrochloric acid, wash thoroughly and dry immediately. Then, get some camphor and rub copiously into the leather item that stores the brass.

Perhaps the vinegar in the ketchup does the job.

That green crud *IS* the patina. Just in a thicker layer.

Preventing the reaction involves stopping oxidization and/or sulphation. Good luck with that using any method other than a protective coating of some kind on the metal, or nearly constant buffing. (which will, of course, keep it bright and shiny) As an example, observe the "wear points" of an in-use item made of brass - Notice that where you grab it to use it stays fairly bright, while "untouched" places develop the crud? As a second example, clean up a piece of brass "nice and bright", buff all finger-schmutz off it, then take a picture of it. Set it down someplace and leave it alone for a while. Depending on the local atmospheric contaminants and the exact alloy used in the piece, it might take anywhere from minutes to days before taking a second picture and comparing it to the first reveals that "the crud" is already re-growing. You're gonna to have to go with "time-lapse photography", since it happens gradually enough that naked-eye observation will be very unlikely to spot it "as it happens". You can often speed up the crud formation significantly by wetting a rag with ammonia solution and putting it in a closed container with the item, but that's a lot like cheating :)

Basically, with brass that isn't coated, you've got two appearances: Bright and shiny - AKA "not enough crud to be visible" - or some level of "not bright and shiny" - AKA "Visible crud" in quantities ranging from "barely any" to "big ol' honkin' chunks that literally flake off if you touch 'em". Patina = "A *VERY* small amount of crud".

DO NOT DO THIS. In other words..This guy doesn't know what he is talking about.

Get a piece of scrap brass and follow his instructions. You will find that the HCL removes zinc from the surface leaving what looks like a piece of copper. The only way to restore the brass look is to physically remove enough surface metal (now copper) to get back to a brass surface.

No, don't do this. Don't mix chlorides with cuprous alloys (brass or bronze). In the short term you get de-zincification and your brass turns pink. In the long term you might get "bronze disease" which is an ongoing chloride corrosion of bronzes and cuprous alloys, and the devil's own job to stop (web search, it's all described)

Most modern leather is now tanned with acidic metal salts, which are a problem for metal corrosion in the future. They're usually OK when dry, but a problem if anything gets damp. Best fix is to use vegetable, animal or oil tanned leathers. A compromise for existing leather is to neutralise the acid in it. Most of the gimmicks posted in this thread so far are bogus.

rec.knives is a good place to read about mettal corrosion with leather.

I have cleaned up brass parts many times doing this. I NEVER said to soak the brass in HCL. I said DIP IT and wash thoroughly and dry immediately.

One can also polish brass with ammonia but again, you want to polish it and wipe it clean. and not soak it.

It's also a good way to darken it deliberately for patination. Funny sort of cleaning and polishing...

Have you ever tried it, Andy?

I don't know anyone that has polished brass with ammonia but I do know a guy that has used it to produce the patination and the green deposits the OP was asking about removing.

The prime ingredient in Brasso is ammonia.

"Robb" wrote in news:45b0a6c6$0$20037$ snipped-for-privacy@per-qv1-newsreader-01.iinet.net.au:

It is.

Straight Vinegar (dilute Acetic Acid) works well and slowly.

I've used the 10+% stuff - normally used for making pickles - to remove surface corrosion (not deep pitting) from both copper and brass prior to polishing.

FWIW, the use of -cheap- ketchup (the cheaper the better) for this purpose was taught to my mother by HER Grandmother.

When she used this to brighten a very old brass urn I thought that she'd "lost it" until (1.) she explained about the -mild- acidity and (2.) I saw the results.

Since then (about 1950) I've used either cheap ketchup or vinegar many times

- especially heavily blackened copper and/or brass.

BTW, a heavy black encrustation may require 1-2 weeks of soaking in ketchup. That's why I usually [now] use strong vinegar.

Wild Bill wrote:

No one seems to have addressed the root cause of the problem. When leather is tanned in the traditional way, tannic acid from oak bark is used to change the protein of the leather to another variant of protein. then its rinced many times to remove as much of the tannin as possible. then treated with vegatable oils and saddle soap and water. All this keeps it supple. On top of this horse harness is cleaned with saddle soap, which is a kind of soap based on sodium hydroxide. these chemicals along with the moisture remainng after tanning and saddle soaping react with the copper in the brass to make copper carbonate amongst other things. Im not talking about other oxides of brass. thats a seperate issue. thats what it is and where it comes from. Unless you can keep the buckles off the leather it will continue to corrode the brass so long as they are in contact. Drying out the leather will reduce it but ruin the leather. so how get rid of it. well, I use an ordinary bowl of warm wash up water, put the buckle and the leather in to soak for a few minutes. then place on a draining board and scrub with an old tooth brush and some form of cleaning scouring powder. Thats asuming you cant take the buckles off easily. Some harness leather work is rivetted or stitched onto the buckle so youll have to scrub the crud off whilst hte buckle and leather are connected. Now if that wont shift it , then get a small scalpel or small pen knife and carefully scrape away at the crud till you see bright metal again. It will take time but restoring anything allways does. thers no quick fix unless you have access to chemicals that make up "bright dip" this works very well but is highly dangerous. you need a fan exhausted fume cupboard to use it.

So any chance of some images? that would make it a lott easier to give a practical answer.

Hope this helps.

========= Thought that some of our ex-military would have popped up by now. Look for Brasso or Blitz cloth. Both will polish brass to a mirror finish and have some protective effect.

see

also

You may want to try coating the item with a very thin layer of clear fingernail polish after cleaning. Military brass / rank insignia was [is?] often plated with a very thin gold that looks like brass. Be aware that using Brasso on plating this thin will remove it.

Unka' George [George McDuffee] ............................... On Theory: Delight at having understood a very abstract and obscure system leads most people to believe in the truth of what it demonstrates.

G. C. Lichtenberg (1742-99), German physicist, philosopher. Aphorisms "Notebook J," aph. 77 (written 1765-99; tr. by R. J. Hollingdale, 1990).

Thanks to all, I appreciate the tips and explanations. As I'd suspected, the lingering acids/chemicals in the leather will need to be addressed.

I guess I'll try to moisten the leather to draw out or neutralize the acidic traces, and try to stuff the leather holders to prevent shrinking while slowly drying.

On Sat, 20 Jan 2007 10:44:38 -0500, with neither quill nor qualm, "Wild Bill" quickly quoth:

If you wrap your item which fits in the holster in plastic, it will also guarantee that the shape of the leather won't change as it dries. Leather is usually molded wet and retains that shape when dry.

-- History is often stranger than fiction. Fiction has to be plausible. History is what happens when people don't follow the script. --pyotr filipivich, RCM

Yep, thanks. I was thinking of trying a wood block wrapped in fabric, to help absorb the moisture (and hopefully some of the lingering acid) out of the leather, while ensuring that the holster would maintain it's shape.

It had occurred to me that making a neutral liner for the holsters would create a barrier between the brass parts and the leather, but experimenting with coatings and/or adhesives, or making patterns of plastic to fit the interiors might be a little too much trouble.

WB metalworking projects