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.
Quote:
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
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