Anyone ever clean gallic potin coins?

[casata137ec]

Evening all. I have never cleaned a true "potin" coin (not a late Alexandrian tet, but a gallic cast potin) before and was wondering if there was anything I should avoid. I am not familiar with the material so I do not know what the corrosion looks like or will do or for that matter what soaks/chems I should avoid. Any advice would be great.

The pic below shows a bit, but most of the top stuff came off in a powdery flurry and what is left looks like old bronze disease (the reddish cast powerdery junk) along with some of the blue greenish powdery stuff that is seen on top. The metal seems very sound, but I am afraid of digging too far.

So far I have just been mechanically cleaning and was wondering if there was anything I should add to the process or avoid altogether.\

Thanks
Chris

[Mayadigger]

Ave Chris,

Never cleaned such a coin. But...what you're describing certainly sounds like, and looks like (at least to me) BD.

Shooting from the hip here, I'd suggest that you treat your Potin with BD Killer as per the instructions, but leave the reverse alone; it appears to be disease free. The following may take a few soaks.

Use any hand-held tool (bamboo skewer, common DP, dried rose thorn, etc.) that works best for you to remove all of the soft green/blue fuzz. Repeat the soaking process until all is removed. Once you are certain that all of the fuzzy bits have been removed, allow your coin to rest in DW for 24-48 hours. Remove and place in your oven for 2-3 hours at 250 degrees to dry it out. At this point it should be BD free, but keep an eye on it; if there is still BD, you'll see it return 30-60 days later.

Best I can do,

Kevin

[casata137ec]

Thanks Kev, that is how I am doing it. Per the article linked below, it seems that: "The word “potin” was the name given by 19th century metallurgists to a special alloy of bronze, which contained an unusually high percentage of tin (up to 25 percent), and quite often an appreciable percentage of lead as well." So, it looks like BD could indeed be the culprit. I'll post after pics when completed.

Chris

PS Pardon this stupid question (and YES, there are stupid questions! lol  ), but would skipping the oven drying be advisable due to the higher lead content?
C.

A pretty good and concise article on gallic potin coinage: http://www.ancientimports.com/introtopotinsofgaul.html

[Robert_Brenchley]

It might be wise to go carefully! I find that if I use a gas oven turned to its lowest level, with the door ajar, it'll gently melt out a comb of beeswax. If wax is safe I'd say potin should be at that sort of setting.

[casata137ec]

Thank you, Robert. That sounds like just the ticket.

Chris

[casata137ec]

All right...it is as done as I am getting it. Potin, it seems, is just as solid as bronze. No issues with heat, and the standard BD treatments do not seem to harm the material. I was suprised to see that the material itself is very brassy and yellow under the dark patina. For full disclosure sake, I hit the obverse with dellars (soaked it up overnight) and then hit it lightly with my silver brush. All in all it turned out pretty good, to my eyes anyway.

Chris

Boviolles(?) Mint, Celtic Gaul, Leuci cast potin, c. 70-52 B.C. Potin, 18.6mm 2.99g, BMC Celtic III 422
O: Crude stylized head l. with three locks of hair, wearing wreath
R: Boar left, fleur-de-lis ornament below