I was inspired by this thread started by @Valentinian, to finally make pictures of a set of five coins I bought two years ago from an old numismatic mentor of mine. I fell for these coins because the envelopes that housed them, mentioned their common origins: they were all sold by the same coin seller in Istanbul, one Jakob, in 1974. Also, they have a common look: large and heavy coins, all between 22.8 and 26.2 gr., all between 30 and 33 mm diameter, and all made of yellow metal, with the same red and dirty patinas. Possibly they were found together, maybe with other coins, there's no way of knowing this. I don't know what generated the red spots. Nor do I know what the caramel-like substance is on one of the coins (I heated it: whatever it is, not caramel). Suggestions how to get of rid of this, are very welcome! However, all five are Caracalla coins (one possibly Elagabalus), four are from Antioch in Pisidia, and one is Imperial Roman. 1. Caracalla (198-217). AE Sestertius, Caracalla. Minted in Rome, year 211. Obv. Laureated bust to the right. M AVREL ANTONINVS PIVS AVG BRIT. Rev. Fortuna seated to the left, shield under throne. FORT RED P M TR P XIIII COS III P P / SC. Orichalcum 30.5 mm, 26.18 gr. This coin is sort-of-an-ancestor of the 19th and 20th century British penny. 2. Caracalla. Obv. Laureate (bearded) bust r. IMP CAE M AVR AN TONINVS PIVS AVG. Rev. Victory walking left, holding wreath. V(ICT D N) COL ANTIOCH/ S R. Orichalcum 33.5 mm, 25.06 gr. Krzyzanowska Group D. 3. Caracalla, 209-211. Obv. Laureate, draped and cuirassed (youthful unbearded) bust r. PIVS AVG ANTONINVS. Rev. Victory walking left, holding wreath. VICTORIAE DDD NNN COL AN(T?)/ S R (See here for varieties, and the Krzyzanowska groups); Orichalcum 32.5 mm, 22.82 gr. DDD NNN = three emperors: Severus, Geta and Caracalla, enjoying the British victory. Krzyzanowska Group F. 4. Caracalla. Laureate (bearded) bust r. IMP (CAE M AVR) ANTONINVS PIVS AVG. Rev. Emperor on horseback t.r. VIRT AVG C(…)/ S R. Orichalcum 31.5 mm, 24.80 gr. Krzyzanowska CAR 34.57; BMC 50; SNG France III 1138; SNG Tuebingen 4364. Looks much like a die link on both sides with the Wildwinds coin (search for SNG France III 1138). Dirty caramel color stain, maybe plastic? 5. Caracalla. Obv. Bust r. PIVS AVG ANTONINVS. Rev. Tyche with palm and cornucopia t.l. GENIVS COL ANTIOCH /S R. Red stains. Orichalcum, 32 mm, 24.86 gr. Some are thinking this might be an Elagabal coin.
I would love to see #3 cleaned up. I love Victorys and it is a shame that she is covered in that stuff, whatever it is.
I have never had success removing red and suspect these coins were harshly cleaned removing the crust and green but leaving the red. Judging just from the portraits, I prefer Caracalla for your coin. The RPC one seems a different style and may be Elagabalus.
I actually kinda like the red on these. Contrasts nicely with the yellow. Whatever it is, physical cleaning never works. Acids, such as lemon juice or oxalic acid, will eat through it eventually if spot applied repeatedly (I know using acids on bronze is anathema most of the time). Takes patience, and may reveal an ugly pit underneath; occasionally there is still detail underneath. But I wouldn't.
Cleaning with sodium hydroxide creates these red deposits. They may be from a heavily encrusted group that was cleaned up with sodium hydroxide. I bought a set of LRBs from a dealer who had a big group that were found all stuck together with encrustations. Sodium hydroxide was used to clean and separate them and they look similar to yours only with even more red. I never had much luck cleaning the red stuff off so I just kept them as they are. John
Thanks for the advice. I think the blob on coin 4 might be removable: it looks like a plastic fluid that was poured on it, then curdled. But how to remove plastic?
As mentioned above, these coins were harshly, but only partially cleaned. If you want to try to improve their appearance--and I am neutral about whether or not you should attempt this--probably your best hope is to take them completely down to bare metal. Electrolysis, monitored closely, is probably the safest method; the coins have already been chemically tortured enough. If you do this, you should allow them to darken and re-tone naturally over time. Artificial patinas tend to make me retch.
Th only reddish patina I have is on this double sestertius of Postumus, the only yellow patina remnant I have is on this sestertius of Severus Alexander, which I suppose was cleaned.
I agree that it’s best to do nothing more. But I need to post some pictures later showing the results of targeted acid cleaning. It’s an involved process, but I think its safer than electrolysis since it allows you to only target problem areas. Electrolysis has a bad tendency to destroy impurities in the metal in random spots, creating pitting. If it’s actually plastic on that one coin, could heating it soften it enough to remove manually? If it’s some kind of glue, maybe acetone?
