Hello everyone! This is my first post on CoinTalk so forgive me if I am in the wrong place. I have a wonderful provincial tetradrachm of the emperor Gallienus with a good amount of verdigris that I am concerned about. I purchased it in this condition, but I would like to stabilize it so it does not degrade further. The green encrustation is relatively hard and does not brush away, but appears like bronze disease. I store it in a 2x2 guardhouse flip in a cool, dry area. Should I be concerned? What would y'all recommend to do? Thanks!
Beautiful coin. You want to do the least you can with that beauty. Perhaps a few soaks in distilled water with light toothbrush brushing then dry a few hours at 200 degrees F before storing in a flip or capsule. Sometimes green is just green...
Very nice Gallienus tet! Are you referring to the green around the edges within the little crevices? I really don't see much on the obverse or reverse, just a tad in the tiny areas. This verdigris is not uncommon in the textured edges of the Alexandrian tet fabric, or on high bronze content tets later in the empire. This is different than bronze disease and what I'm seeing is nothing that I'd personally be concerned about. Bronze disease, when active, creates a white powder that can easily come off with some poking... These green verdigris instead should be hard. Are you seeing it grow at all? I would doubt it as I'd suspect it formed in the environment prior to its discovery (unless you are recreating an environment like that). In honor of your coin, here are some of my favorite Gallienus tets: Gallienus, Ruled 253-268 AD AE Tetradrachm, Egypt, Alexandria Struck 262/263 AD Obverse: AYT K Π ΛIK ΓAΛΛIHNOC CEB, laureate and cuirassed bust right. Reverse: Eagle standing left, head right, holding wreath in beak; before, palm; behind, LI, RY 10. References: Emmett 3806, Dattari 5276 Size: 23mm, 11.9g Gallienus, Ruled 253-268 AD BL Tetradrachm, Egypt, Alexandria Struck 261/262 AD Obverse: AVT K Π ΛIK ΓAΛΛIHNOC CEB, laureate and cuirassed bust right, seen from front, slight drapery on left shoulder. Reverse: Eagle standing left, holding wreath in beak, palm over shoulder, ENATOV to left and L to right (year 9=261/262 AD). References: Emmett 3802, Dattari 5286, Köln 2908 Gallienus, Ruled 253-268 AD BL Tetradrachm, Egypt, Alexandria Struck 263/264 AD Obverse: AVT K Π ΛIK ΓAΛΛIHNOC CЄB, laureate, draped and cuirassed bust right. Reverse: Tyche standing left, holding rudder and cornucopiae; L IA (retrograde) in left field, RY 11. References: Emmett 3836, Dattari 5267 Size: 24mm, 9.69g Notes: Fascinating retrograde date.
@Justin Lee Thank you! The green is in the recesses on both sides of the coin, around the legend, and in the deep pores along the edge. It actually makes the coin look nicer in my opinion, highlighting the portrait with its greenish hue. It is hard to see in some of the photos though, but appears similar to the green in that final Gallienus tet image you posted. The green is not spreading or aggressive from what I can see. It did come off with some prodding when I prodded the edge recesses with a toothpick. Would you recommend soaking it and brushing with a toothbrush as @Kentucky said? I also have heard of sodium sesquicarbonate as a neutralizing agent. What do y'all think? I am relatively new to ancient coins and have been trying to make sure I am not overlooking their preservation. It's just been confusing to identify verdigris vs. bronze disease vs. patina, e.t.c. I appreciate all the feedback.
That is a beautiful coin! I honestly don't know if I'd mess with it at all. As long as it isn't bronze disease, I'd leave it be.
I own many tets with that kind of green, if none of it budges with a toothpick, it isn't BD, just copper. But it's still worth keeping an eye on because sometimes that green does turn to BD and then it's distilled water for a while and pick away. But it's best to not piss it off now and maybe make things worse.
Bronze Disease (often shortened to BD on here and elsewhere) is powdery in texture and parts can come off with little manipulation. It also appears to be replacing the metal of the coin with itself (it is), versus appearing atop the coin as in patina and the like. Here are some photos (not mine) of BD... Here's a coin of mine that has a speckled green verdigris coating like it was sprayed with it lol: It's hard and stable. You're doing great with maintaining your coin by asking questions, and I think just keeping a frequent eye on this one to make sure it stays just the way it is is exactly what the doctor ordered.
Welcome to Coin Talk, JJoyner. That is a fine looking Roman tetradrachm you have and I agree with those who suggest to just leave it as is. One of my favorite aspects of ancient collecting is the colors that accumulate over the centuries. Your coin looks great - great surfaces and colors - in my opinion. Last week I got a small batch of Roman tets off eBay, and as you can see from this photo, two in the bottom row have gone a bit green. This green is hard, not powdery, so I am pretty sure they are disease-free, but I'll keep an eye on them. Just a tip on posting here - if you hit the "full image" button next to your uploaded photo, it will appear in your post full-sized.
Your coin does not have bronze disease. Justin Lee did a good job of explaining the difference between verdigris and BD. And I agree with you: the verdigris actually adds to its appearance. However, not only should you keep an eye on it, you should take it out of its flip, hold it in your hand and think: "Wow. Ancient Alexandria. This is so cool!"
No real problem with the coin. In fact it is surely a keeper. Just watch over it to make sure BD doesn't show up, and it probably won't.
Great coin and post, @JJoyner ! I generally leave mine alone. I like how @Mat said it: You just don't want to p them off! Here is my Gallienus Ant with a goober. I just watch it, but leave it alone. It is a hard mineral without flaking. RI Gallienus 253-268 CE Ant Milan mint Laetitia S -secunda
I have ancients with green "toning"/verdigris and have bathed them and toothbrushed them and they were none the worse for it.
A poor cleaning job involving water is more likely to start bronze disease. Don't take medicine for ailments you do not have.
