Moe (fl) said:
Thanks for the replies. Here is some more information.
The pendant could be pewter. Last weekend, it started to look a little brittle when dried, so I put it in distilled water for a couple of days. I think this was not such a good idea because when I took it out the metal was coming off a little. I got gray on my fingers. I rinsed it with water and let it dry. Now it looks brittle again and perhaps lost a tiny layer of metal. Any ideas of what to do to preserve?
The coin like item is smaller than a dime so it could not be a penny. It is very thin copper/brass. The edge looks copper but the rest looks plated or brass.
The iron slug is mildly magnetic (not strong which could mean that it has lost iron ions over time). The blade piece is not magnetic so I am wondering what type of metal it could be. Any guesses? I will start electrolysis this weekend.
-Moe
You should keep (until you know what it is and what you must do with it) all finds - if you are not sure what it is - in the SAME environment that you found it in. So you should have kept it in for instance in some sand and water from the sea. That is the environment that it has lived in for some time, and it will not deteriorate fast in it, it is used to it and the metal has built up protection layer against deterioration (oxides like rust, tin oxide, lead oxide).
Taking it out of that environment, washing it with tap water or putting it in distilled water and then letting it dry and be exposed to the air, will immediately cause the material to begin again oxidize. I have seen nice coins coming from about 3 meters deep in a muddy pit here deteriorate before the person could get home, because he just put it in his bag. At home the nice but thin silver coin was just in pieces and dust. I am not kidding around, the oxygen works immediately to start oxidizing the piece. If coming from a dry area, just put something in a plastic bag to protect it. But something coming from mud or from immersing in water you have to handle otherwise, if you are planning to keep it. When we find a valuable object deep in the mud we pick up a handfull of mud, put the coin in it, and seal it in a plastic bag.
Putting it in distilled water, letting it dry out, and then leaving it unprotected against oxygen was not good. Distilled water is totally empty of salts and minerals, and because everything in nature tries to balance out, it just sucks the salts and minerals out of the object. The object becomes less materialized and lighter. Distilled water can still be used to remove salts and minerals from objects - it works very fast -, in fact I use it myself to get the salts out of some of my finds, but not more than a couple of hours or less for a coin, and only longer with larger items. Then it MUST be protected. If not it will start oxidizing very fast as you have seen. The professionals start out with distilled water, and measure the water content for minerals and salts. When the water reaches a certain point they stop, and replace the water. Then continue until they have reached a desired level. We cannot do that at home, its all guess work.
The powder you got on your fingers was oxide, I would think tin or lead oxide, or a compound of those. If the object is lead it is soft, you should see places were scratches and such have occurred. But I would guess tin or a mixture of tin and lead called pewter (a mix of 85-99% tin and the rest lead or other metals). Here are some professional writings on the subject:
Tin seldom survives in archaeological sites because of the transformation of tin to a mix of oxides by direct oxidation or to a loose powdery gray tin, commonly referred to as 'tin pest,' by allotropic modification. The changing of compounds of tin in a marine environment have not been adequately studied; it is known, however, that sodium chloride stimulates the corrosion of tin. Ingots of tin that were completely oxidized to tin oxide were recovered from a Bronze Age shipwreck off the coast of Turkey".
Lead alloys, such as old pewter, which is an alloy of tin and lead, oxidize to the same compounds as the two parent metals. Conservation of lead, tin, and pewter: Once recovered from the sea, the corrosion products of objects of lead, tin and their alloy, pewter, are stable. The corrosion products may be unsightly or even disfiguring, but they do not take part in chemical reactions that attack the remaining metal. The objects should be cleaned only for aesthetic reasons and to reveal surface details under the corrosion layers. Old pewter, an alloy of lead and tin, must be treated as tin, which is the more anodic and chemically sensitive metal. Therefore, no acids, or sodium hydroxide should be used, unless, in the case of electrolysis, the metal is given cathodic protection.
The only conservation alternative for badly oxidized tin objects is to consolidate them in microcrystalline wax or embed them in a plastic material. Slow, extended diffusion of chlorides in an alkaline solution is not an option due to the solvent action of the solution on tin objects.
You must seal the object, the object is dried with hot air and then the fragile metal is strengthened and protected from atmospheric corrosion by submersion in molten microcrystalline wax.
What this really means is that by removing the outer layers of salts and oxides (which were built up over time by the metal in your hanger to protect itself) by putting it in distilled water, you removed the stable corrosion layers which were protecting the object. That in itself is not the problem, we do that many times to make something look pretty. But you must seal the object after the oxide products are removed.
Sorry to have made such a long text, but wanted you to know how to do it the next time. Maybe others can improve what I have said, I am not a professional, just a searcher....
About the coin like item, if its has been plated it is not a coin, or if it is a coin its an fake.
