De-rusting and etching Damascus gun barrel

[estcrh]

Here is a rust removal process used by Ian Bottomley (Curator Emeritus of Oriental Collections at the Royal Armouries Museum based in Leeds). This was originally posted on the Samurai Armour Forum, Ian has had a lot of experience stabilizing and restoring Japanese armor, his process my be helpful to some forum members.

All, I thought I would just publish details of a russet mask undergoing cleaning. The mask in question was very badly spotted with secondary rusting, some of which had developed into quite bad active rust encrustations. I used my usual mixture of boiled linseed oil thinned with white spirit in a ratio of approximately 50 / 50 - it isn't critical. The mixture was applied with a paint brush over a small area and allowed to soak in for a few minutes before rubbing the area with a chisel shaped piece of stag antler. You can see that it is working because the secondary rust comes off and forms a brown slurry which you need to wipe off with tissue. Some of the bad rusting was particularly stubborn and needed considerable pressure on the antler and repeated applications of oil to remove it. You can tell when you have managed to get the area clean because the antler slides smoothly over the surface. When finished it still looked a bit marked so I resorted to lightly rubbing the oiled surface with fine wire-wool. Again, more rust came off and gradually a fairly clean surface was obtained. I will give it a week or so for the oil to oxidise then I will finish it off with a coat of wax.
Ian Bottomley

I did think long and hard about how to treat these pieces as well as the consequence of doing nothing. I include a picture of the surface of the helmet which I have yet to tackle. You will note the extensive patches of secondary rusting, some of which are beginning to become serious. Rust is hygroscopic, attracting moisture from the atmosphere and converting more of the iron back to its stable oxide. Left alone, this secondary rusting would eventually have destroyed all of the original russet surface. I could have just covered the whole thing in a sealing coat of oil or lacquer, but to my mind it would have looked terrible. Yes, the treatment might take off a minute amount of the original russet, but very little if done with care. I also include an image of the surface of the mask which has had as much cleaning as it is going to get. You will note the slight etching of the original surface where the rust patches were. Sadly there is no way of restoring this damage, only making it as inconspicuous as possible. I will give it a light coating of wax in a couple of weeks which will help. When new, the helmet and mask would not have been covered in unsightly blotches of rust and I see no logical reason to keep it that way. The only downside may be that the surface looks slightly darker. Even this sis debatable since the original russet would have been oiled or lacquered to preserve it. The ultimate fate of all iron is to revert back to its stable oxide. Short of keeping it in a vacuum, all we can do is to try and prevent it reacting with oxygen and water. This treatment will only last a certain length of time, but at least it delays the inevitable.
Ian B

[RDGAC]

Hah! I got as far as getting the FeCl, but have yet to get round to trying it. Partly this was from caution, partly from lack of a suitable workspace, and partly from a lack of time. We're hoping to get a Heritage Lottery Fund grant for a refurbishment, so (in the hope that we will), lots of frenetic admin activity has been taking place over the past 14 months. It's all excitement and adventure, at least until the money runs out.

I like the look of this process, estrch. I've met Ian - he very kindly came to look at our small collection of Japanese swords from the 2nd World War - and he's a thoroughly good bloke, not to mention exceptionally well-versed in all matters Japanese arms and armour (as you are doubtless well aware). Any preparation with his seal of approval probably deserves a crack; this one, moreover, sounds a lot less potentially invasive than the acid route, albeit far more time-consuming. Only one thing puzzles me - where the hell I'm going to find a bit of deer antler...

- Meredydd (aka Harassed of York)

[Iain]

Antler technique sounds intriguing. New one to me! There seem to be plenty of antlers about on UK eBay. I'm in a rural area myself and shouldn't have a problem to get a piece. The results displayed look promising, however I would imagine steel wool and oil would get the same result?

[RDGAC]

Originally Posted by Iain

Antler technique sounds intriguing. New one to me! There seem to be plenty of antlers about on UK eBay. I'm in a rural area myself and shouldn't have a problem to get a piece. The results displayed look promising, however I would imagine steel wool and oil would get the same result?

Not sure. I've worked this barrel quite extensively with wire wool and oil, and although it's removed the looser rust on the surface, it seems to have minimal effect on the tougher, older deposits. It also struggles to remove rust from pits in the steel. Presumably the antler, especially with that shape, is better for scraping it away without being hard enough to damage iron or steel.

The thought has just occurred to me, too, that these "antler" things have been known to fall off strange, quadruped beings known as "deers". Being a city boy, I doubt such things really exist; however, I hear one can actually pick them up in places, if one knows where to look!

[estcrh]

Originally Posted by RDGAC

Not sure. I've worked this barrel quite extensively with wire wool and oil, and although it's removed the looser rust on the surface, it seems to have minimal effect on the tougher, older deposits. It also struggles to remove rust from pits in the steel. Presumably the antler, especially with that shape, is better for scraping it away without being hard enough to damage iron or steel.

The thought has just occurred to me, too, that these "antler" things have been known to fall off strange, quadruped beings known as "deers". Being a city boy, I doubt such things really exist; however, I hear one can actually pick them up in places, if one knows where to look!

Its those raised, hardened deposits that are difficult to remove, I have an old Japanese matchlock barrel that I have the same problem with, it has raised deposits of rust, I did not have any antler available so I used a piece of shaped bone (recommended by another expert), this works well. I was told by the same expert that for really hard to remove spots that he uses a piece of knife sharpening stone as an abrasive, he said this was a last resort and to be very careful as the sharpening stone could damage the surface.

[Dmitry]

Originally Posted by Iain

Antler technique sounds intriguing. New one to me!

Me as well. I sometimes use sharpened pieces of wood, but antler makes sense. It's softer than steel, but harder than rust. Sometimes I coat the surfaces with BreakFree CLP penetrating oil and let the item sit for a week, before I "take the knife" to it. My feeling is that the oil will sufficiently penetrate and soften the rust in that time-span.

[RDGAC]

Bone would likely be easier to get; antler isn't exactly easy to acquire here nowadays, it seems. I'm tempted to see if I can find an old antler walking stick and trim the handle off, but a lot of these are probably plastic nowadays.

In either case, I will (eventually) get round to this, I promise!

Thanks for the tip re: 3M papers, Dave. I think I'm familiar with them as "wet 'n' dry", used to use them for getting a nice, shiny finish on brass controls on steam engines (under advice, might I add, for anyone wincing). I've considered them but think I'd prefer to try the bone/antler trick first, since it seems even less likely to damage the metal. However, I've used wet & dry for some polishing in the past, and it is, as you say, highly controllable.

Best,

Meredydd

[DaveA]

If you are looking for an abrasive, I highly recommend that you control the grain size. Other members have commented on the need to control hardness and force used when removing rust. Grain size in your abrasive is also important.

I have had excellent fortune with a product called "37-948 3M Micron Polishing Papers" available from Amazon and elsewhere. It comes as a 6 piece pack of 8 ½ x 11 inch papers in assorted grain sizes ranging from 30 microns to 1 micron. They are color coded so you can easily recognize which is which; otherwise it would be very difficult. The particles on the paper are micron graded aluminum oxide and silicone carbide in a slurry that is affixed to the very flexible backing material. When you work with grains at the micron level, it does not leave visible marks and it is easy to control how much material you want to remove by choosing the right size. The smaller grain sizes, when used in sequence larger to smaller, bring a super luster shine to the metal. That said, if you use the 30 micron size with lots of pressure and over a long time, you are definitely stripping more metal off than you should!

The 3M papers are nearly indestructible and the papers can be used again and again. The paper does not rip or separate, even with vigorous use. I typically cut a small piece for easy handling. They work wet or dry, on flat or curved surfaces with ease.

Best Regards,

Dave A.

[Dmitry]

DaveA, can you post examples of the work you've done with the 3M papers? I'm always keen on finding new ways to clean and preserve. Thanks.