This Nero fourree denarius has been in my collection for quite a while, actually, it was one of the first ancient coins I acquired as part of a group lot of 26 denari. I decided that it would need some restoration, but thought it wise to first gain some experience on 'normal', denari before burning my hands on a fourree. Up until this this evening, that is. So, here is the starting point: Basically, at the start of any cleaning project, I take a 'before-photo', and zoom in as far as possible (click to enlarge the image). There are some major issues with this coin: it's a fourree, with a copper core (instead of e.g. iron, which may also be encountered). The copper is exposed mainly at the reverse, but also at the hairline of Nero on the obverse. there is a layer of dirt, mainly on the reverse (the brownish layer), but also on the obverse (in the hair, the eyes, and the mouth) The coin is bent (starting at the "R" from "NERO", to the small flan crack at 11'o clock on the obverse, and neer the feet of Jupiter at the reverse) The dark spots at the head (cheeks, neck, and below the neck) are probably horn silver. This specific type of horn silver (black spots) are usually difficult to remove) On the other hand, the pro's: The obverse is nicely detailed The silver layer is rather thick, as witnessed at 2'o clock on the obverse (partly curling back Cleaning a fourree should be done with extreme care, as it is super easy to break the thin layer of silver and pierce into the (often rotting) core. In this case, I decided that the regular soaking in organic acid (synthetic citric acid, a weak acid) was obviously not possible. The core seemed strong (no indentations of the silver, not too many cracks in the silver), so mechanical cleaning with a bamboo toothpick seemed a good starting point. After removing most of the dirt, the coin was gently scrubbed with baking soda (sodium bicarbonate). This has two functions: a) it is very effective on remaining dirt, b) neutralization of acids. The downside is, that the coin is shiny as if new. The horn silver spots were mostly removed using the sodium thiousulphate approach (see my post history for more details). Another benefit of sodium thiosulphate is that it darkens the coin, resulting in a 'cabinet toning' kind of patina (grayish silver). The obverse improved, with more details of the head visible. As expected, the horn silver spots did not completely disappear. I was not fully satisfied with the reverse, so I repeated the procedure, until: ROMAN IMPERIAL, Nero Denomination: Fourree AR denarius, minted: Rome, Italy; 64-65 AD. Obv: NERO CAESAR AVGVSTVS: Head of Nero, laureate, right, with beard Rev: IVPPITER CVSTOS: Jupiter, bare to waist, cloak round lower limbs, seated, left on throne, holding thunderbolt in right hand and long sceptre in left Weight: 2.35g; Ø:1.8mm, Catalogue: RIC I 53, Provenance: Ex priv col; acq.: 12-2018 Feel free to post anything you deem relevant!
Excellent job. I've got a cleaning project coming up soon with a well encrusted As, so I hope to do a similar report as yours here. My approach so far has been distilled water and toothpicks, but I recently got hold of some Le Crayon a Andre, and they did wonders with my Carausius coin, so I hope to primarily use those again.
For the Nero, you might be well served by depositing some VerdiCare on the reverse and massaging it in with a cotton swab after letting it soak a bit.
