Hello all, attached is a front and back photo of a cool Holland Society of New York Medal (1904) medal I recently acquired. As you can see, the obverse is pretty covered in crap and doesn't have good eye appeal. What would the best way to remove it be? Would I just use some sort of bronze cleaner? I don't want to be the guy to clean a valuable coin or anything but I only paid a few dollars for it and if this green stuff already damages it, I rather the damage at least look nicer if that makes any sense. Any input would be appreciated!
The "gunk" is corrosion that has already destroyed the medal's surface. The ONLY way to treat it is in a "SOAK." No rubbing! Perhaps someone on the forum can tell you one of the commonly available chemicals to use.
This doesn’t appear to be verdigris or PVC residue. It appears to be actual corrosion. This is tough. You can use sodium thiosulfate to remove iron oxides, and hydroxide tends to work out alright for copper oxides. The two pics below are before and after using hydroxide, thiosulfate, and vinegar. using harsh chemicals will strip all patina away, but it’s a sacrifice that you have to decide whether you’re willing to make
Thats a solid before and after! If I can replicate those results Id be happy. I only paid a couple bucks for the medal and it not worth hundreds so that is a sacrifice would try. Is sodium thiosulfate something I can easily buy? I am not well versed in chemicals at all. I only recently bought acetone for another coin project and that was a learning experience for me
You can get thiosulfate for around $6-8 on eBay. I don’t know about where to find that in an actual store, but it was easily shipped to me off eBay. I’d recommend soaking a pre-1982 Lincoln cent in the chemical just so you can get a visual on what impact it has on the surfaces
Awesome good idea. I checked eBay but all I see is sodium thiosulfate and its just a powder. DO I buy that and mix a small amount with water? Sorry if this is an obvious question but I've never worked with this stuff before or even heard of it
Is sodium thiosulfate pentahydrate the same thing? I see 4 oz bottles for like 6.99 and figured that's what I would grab but dont know if the "pentahydrate" is okay or not. Thanks again for the help I really appreciate it
Yup, that’s the one. It should work pretty well, if my past results are any indication. Pretty cheap chemical and will last you forever
Hey so I just got the chemical! How long should I soak for, like are we talking minutes or hours? Also warm vs cold water? I know you also said you just eyeball it but how much are we talking? Hope you don't mind the few questions, I've just never done this and dont know the usual protocol!
I would probably put half teaspoon per 4 ounces or something like that. I would try half hour to start, and then increase time if necessary. take it out, rinse it and see how it looks. If it’s not there then plop it back in for another hour. Rinse and repeat, literally
