There seems to be a Verdicare shortage, or so I've heard. Verdicare is a chemical used to treat verdigris, which tends to be a rock-hard, dark green substance that collects on the surface of the coin. Although verdigris is usually inert and won't cause too much further damage, it does look pretty ugly. From @tenbobbit I received two Postumus coins that were severely affected by verdigris. Knowing that lye seems to be a miracle solution, I tossed the coins into a haphazardly-mixed lye solution for about 6 hours and the results were magical. Billon/silver washed Pax reverse: Billon/silver washed Oriens reverse: As you can see, the lye treatment all but eliminated all traces of tche verdigris, for the most part. There is still a little left on the body of Oriens and the face of Postumus on the Pax coin, but overall, I think this is a 100% improvement. PROS: removes 95-99% of verdigris from surface can reveal previously-hidden silvering seems to brighten up silvering significantly CONS: softens out some details (see the NS in ORIENS, and the sharpness of the POSTVMVS legends) Overall, I think this is a great result. DISCLAIMER: only subject to coins that are either a) inexpensive or b) guinea pigs as you can, and will, ruin some coins with lye. Do not soak any of your 4-figure coins in lye, no matter what.
I tried vinegar on a silver denarius and didn't really like the relatively porous surface it left; lye seems to leave coin surfaces relatively safe
I think lye has sodium hydroxide, so it should be alkaline instead. Still, not a gentle treatment! But I can't argue with the results if they look good.
You and lye man... I'm a bit scared. I've seen a lot of stuff about people disolving bodies in lye. I'm affraid to ask what your other hobbies are
The way I see it, there coins were entirely unpresentable, now they at least look reasonable. I do agree that some details were lost, but the verdigris was quite savage and unrelenting. It's one of things where you can't really win...
My main interest is Postumus and the gallo-roman empire, so let me tell you: don´t collect them. This "unpresentable" way is a very usual way they come up, I have many and I like them as they are. Different points of view, I guess.
I have a couple Postumus coins that look rather attractive. Probably my favorite coin in the entire collection is this one (which was not cleaned my me)
Not a bad result at all. All things considered I do not think you let that much detail. One of the things I usually do with coin that I have used a chemical cleaning process on is to let it soak in distilled water for a while to neutralize any chemical residue. Is this a practice that you use also?
For these I let them neutralize a bit in vinegar for a short while, and then soak in distilled water for several hours to make sure that I don’t end up with nasty surprises in the future...