Many countries used zinc as their coining metal in the WWII era. And zinc is a highly reactive metal, particularly in a moist atmosphere. Lots of my world birth year set has zinc coins; they just do not look good. But I don't expect to be able to replace them with quality coins. So I'm going to go ahead and clean them. Here's a "before": Two questions: 1. What is the best way to clean them? Acid will work but will easily eat them up (remember high school chemistry and producing hydrogen gas with zinc in acid, generally hydrochloric). Is there something gentler? 2. Once cleaned, what is the best way to preserve them? In the old days I think coating them with lacquer was used.
If you have several zinc coins, I would try something different in each. lye tends not to dissolve copper, silver or gold, so that might be an option. Again, don’t do anything with coins you care about
Interesting experiment. May I suggest 1943 cents as experimental subjects. Mild acids such as lemon juice, alkali, brass brush brushing, Ren wax, etc...
So far the best suggestion I can find online for cleaning zinc is white vinegar. It's mildly acidic (acetic acid). Soaking time is measured in hours (6 to 12). Whether it works on zinc oxide (ZnO) I don't know. I'm okay with doing that; I'll give it a try. There are plenty of cheap zinc coins out there. But then comes the process of protecting the coin's surface. The best suggestion I've seen is Japanese lacquer. But that's a "Huh?" Can't find any source for it, not even a reference about it. I'm probably going to go with a quality clear lacquer.
Commonly used on ancient coins is Renaissance Wax I have been experimenting with using linseed oil. Linseed oil is the oil that is used in oil paint. It is a liquid that hardens to a plastic coating on exposure to air.
I have never tried Ren Wax on a zinc coin, but it really works wonders on ancient coins. The main thing it does, in my experience, is darken the overall color slightly; it will generally even out any areas that are much lighter in color than the rest. In other words, I suspect that it will be able to both even out the white ZnO deposits, and make the entire coin a bit darker. It also provides an exterior coating that should prevent further oxidation.
I just bought a bunch of cheap zinc coins that I will use for practice. I'll try to do a "before and after" so that people may get an idea what and what not to do. Think of me as a guinea pig.
Try it on a discard before something you are attempting to restore. Remember, any type cleaning will more than likely devalue the coin.
Good luck with this. I would be very interested to know what works. I suspect nothing chemical will work satisfactorily because the problem is not just oxidation. Zinc crystallizes and even crumbles, especially as it changes temperatures. This is part of the problem with the zinc Lincoln cents and why I don't buy any of them.
I'm wondering how the white vinegar soak, followed by some time in mineral oil, and a gentle drying, would work. Not that I'm speaking from experience..
Found this here http://www.anythinganywhere.com/info/clean.htm when I was thinking about cleaning some WWII coins I have: "When you get an Unc piece of zinc or tin you need to put it in an inert holder immediately if not yesterday. It's probably too late already. These things suck up oxygen and grow spots in the dark. You can then clean the spots off with acid, but they ALWAYS leave pits. You can always tell when zinc has been cleaned. Other than soapy water for dirt and organic solvent for pvc scuzz (you're probably too late) I wouldn't bother trying to clean zinc or tin." and at this site (German): http://www.sammlermuenzen.de/muenzen-sammeln/muenzen-reinigen/#zink they say that zinc is a base metal that oxidizes easily forming a gray to white coating. Zinc is not easy to clean. The easiest way is to use sodium bicarbonate. The gray to white coating can be transformed into the original dark gray color of zinc with gun oil, which probably has the same effect as Renaissance Wax Worst of all is the zinc pest against which there is no cure. This is the original recommendation in German: "Zink ist ein unedles Metall und oxidiert leicht, dabei bildet sich dann ein grauer bis weißer Überzug. Schlimmer noch ist die Zinkpest oder der Zinkfraß. Dagegen gibt es leider kein Mittel. Das eher unansehnliche Metall ist nicht leicht zu reinigen. Am besten versuchen Sie es mit Natronpulver. Den grauen bis weißen Belag verwandeln Sie mit etwas Waffenöl (z. B. Balistol, gibt es für wenig Geld im Baumarkt) wieder in die ursprüngliche dunkelgraue Farbe von Zink. Sollte die Münze bereits von der sogenannten Zinkpest oder dem Zinkfraß befallen sein, gibt es dagegen kein Mittel." Hope this helps
Following this thread; thanks @kanga for starting it. I have numerous zinc coins my father brought home from WW II Europe that I've never dared to clean. Steve
Just for info :Real Japanese lacquer is an organic substance made from the sap of the Urushi tree (Rhus verniciflua). The sap is collected by scratching the tree and is then refined and aged. Wiki. European Lacquer comes from secretions female lac beetles leaves on branches along with other beetle excretement. This is diluted with alcohol to use on classic hardwood. Box store Lacquer can be mixtures of European lacquer with a mixture of organic chemicals and epoxies and colorants.
I Googled "glass brush" as I wondered why that was specified. I have perhaps a dozen brushes but do not know what would be an equivalent: an old, soft tooth brush perhaps? Something stiffer? Steve
Below is Weller's description of a glass brush. I think where he mentions thickness, he's writing about the bundle of fibers, not single fibers. Cal
The brush I have seen mentioned most often is an old toothbrush where you have cut the bristles to half length to stiffen them. Pain to cut those bristles though...
