Should you clean your coins?
One of the first rules you learn as a collector is “never clean your coins”. We are told that we’re likely to only damage them, rather than improve them, and make them less attractive, perhaps even significantly decreasing their value. While this is mostly a rule that has been borrowed from collectors of modern coinage, it still often is used among ancient coin collectors but primarily when it comes to newer collectors. Often, newer collectors will mistake patina or toning for something that should be removed through cleaning. Not only are they likely to remove attractive qualities of the coin, they also risk damaging the coin itself. But as you become more experienced as a collector, learning how to identify a coin that can be cleaned, and how to properly clean it, is a useful skill.
Virtually all ancient coins are cleaned before they are put up for sale but they’re not always cleaned completely. This may be due to limitations in time, skill, knowledge, or equipment on part of the person who processed the coin after it was discovered. It may also be a financial decision where they have determined that more time spent cleaning the coin likely won’t result in a higher sale price. A collector, however, does not always have the same constraints and may be able to spend significantly more time on cleaning a coin. If you can acquire the necessary skills and knowledge to clean coins, you can then take advantage of the lower sale prices of partially uncleaned coins. It may also be the case that deposits on a coin sufficiently hide the quality of the coin and when cleaned you end up with a much better coin than you, or other bidders, expected.
Considerations
When I consider buying a coin that requires cleaning, I try to answer two main questions: (1) what will the coin look like when cleaned; and, (2) what are the deposits and how can I remove them. The first question is as important as the second; there are many coins that can be cleaned but that would not benefit from further cleaning. These are coins with bad surfaces such as porosity, delamination, and damage from corrosion. You may be able to remove the deposits on top but if the coin is still unattractive underneath it’s probably not worth it. Some coins like this can look even worse once you uncover all of the surfaces as the deposits were otherwise hiding some of the unattractive qualities. In the same sense that you can have “tasteful toning”, I believe you can also have “tasteful deposits”, which do not hide any details but do obscure some surface issues or otherwise provide contrast to the devices and help them “pop”.
After you’ve determined whether the coin is likely to be improved by cleaning, next you have to ask yourself if you have the skills to do it. Part of this is understanding what you’re dealing with: is it merely hardened earthen deposits or some staining, or is it a hard copper, iron, or silver mineral such as horn silver and iron oxide? Or, if you’re dealing with bronze coins, is it the dreaded bronze disease? Being able to know which is which from a photo is key to ensuring you don’t waste your money a coin that either can’t, or shouldn’t, be cleaned. Though unless intimately familiar with mineral deposits or are experienced with cleaning ancient coins, it’s always going to be a bit of a gamble. For example, even if you can identify horn silver correctly, it may be difficult to tell whether removing the horn silver will reveal an otherwise untouched surface, or one that shows damage from the corrosive effects of horn silver.
Cleaning Examples: Before and After
To illustrate the points above and more, I will compare before-and-after photos of some of the coins I have cleaned over the past few years. I don’t intend to claim that these coins were all cleaned perfectly, in either method or execution, but I am happy with the majority of them and have learnt many skills along the way that have helped me improve with time. This is also not meant to be a guide on how to clean ancient coins, merely a resource that others may find helpful or interesting.
Scroll through the page to see the different examples or click one of the links below to jump to a specific coin.
Use the tools in the top left corner of each image viewer to zoom in/out, return to the default view, or drag the slider from left to right to reveal the before and after images.
1. Alexander III “Amphipolis” Tetradrachm
2. Demetrios II “Damaskos” Tetradrachm
3. Antiochos VIII “Antioch” Tetradrachm
6. Alexander III “Arados” Tetradrachm
7. Lysimachos “Lampsakos” Tetradrachm
8. Alexander I Balas “Antioch” Tetradrachm
9. Alexander III “Babylon” Tetradrachm
10. Paphos “Bull/Eagle” Stater
11. Antiochos I “Seleucia” Tetradrachm
12. Mark Antony “Ephesus” Cistophorus
15. Alexander III “Rhodes” Tetradrachm
16. Philip III “Babylon” Tetradrachm
17. Seleukos II “Antioch” Tetradrachm
1. Alexander III “Amphipolis” Tetradrachm
This coin did not require much cleaning and I owned it for perhaps a year without attempting anything. My goal was to clean up some of the spotty black and earthen deposits on the obverse, which I found distracting. This would come at the cost of losing some of the natural toning but I believed the coin would be overall improved and the toning would eventually come back.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
Methods:
Though I suspected there wasn’t much, or any, horn silver, I used ammonium thiosulfate anyway as it does not damage silver coins in general and is capable of removing more than just horn silver. I always start with acetone to clean the surfaces of any oils or residues before moving on to solutions like ammonium thiosulfate. I apply the solution with eye droppers in the necessary areas and leave to soak for 30s. I then use a toothpick it try and remove the deposits. If they don’t show any signs of budging, I leave the solution to soak for longer, increasing in 30s intervals, until I see some progress. This can be a repetitive and time consuming process but it’s best to proceed slowly. When the deposits come loose from the surface, be sure not to push them into the surface with the toothpick and try to keep the tip of the toothpick clean, swapping it out for new toothpicks frequently. Cotton swabs can help apply the solution to specific areas and also can remove some lighter deposits over a wider area where it would be risky to use a toothpick in a wide scraping motion.
2. Demetrios II “Damaskos” Tetradrachm
Initially I didn’t clean this coin as it was one of the first coins I bought that could actually benefit from cleaning and I lacked the skill to do so at the time. After some months and practice on other coins, I decided to treat the coin with a thiosulfate solution to tackle the black deposits. They didn’t appear to be horn silver but from experience with other coins, I knew that thiosulfate would have the best chance of removing them.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
- Tombow Mono Zero Eraser – 2.3mm
Methods:
Similar to the previous coin, I went through a process of applying the thiosulfate solution to specific areas and using toothpicks and cotton swabs to slowly remove the deposits bit by bit. This required many “passes” to clean most of the deposits off but they were removed with relative ease. Some staining remained from where the deposits were but this did not bother me much so I didn’t attempt to remove it. As often happens after treating a coin with thiosulfate, a dark yellowy-brown patina coated the coin and gave it a very dull appearance. So far, the only effective way I’ve found to remove this is with mechanical means such as friction. I personally use a small 2.3mm eraser and lightly brush it over the surface. I will cut the end of the eraser to a fine point to clean between legends and between hair curls in the portrait. It’s important that both the eraser and surface of the coin are clean, you do not want to rub mineral deposits that you have just removed into the coin’s surface as this may scratch it. I also don’t recommend this method for coins with lustrous surfaces.
3. Antiochos VIII “Antioch” Tetradrachm
This coin, and others of the same type sold in the same auction, had an unusual coppery-red deposit that was quite unlike anything I had seen before. When I bought the coin, I was resigned to the fact that I may not be able to remove the deposits but I wanted to try anyway. Worst case, I still liked the coin as is. To my surprise, the deposits were removed relatively quickly and easily with ammonium thiosulfate. This was another example where I had found that thiosulfate worked with more than just horn silver.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
- Tombow Mono Zero Eraser – 2.3mm
Methods:
Same thiosulfate treatment as with earlier coins, though I found these coppery deposits were more easily removed than for the black-ish deposits I was used to dealing with. After treatment, this coin turned a very yellowy-brown colour due to the thiosulfate and required extensive cleaning with the eraser to restore the silver colour of the surface.
4. Athens “Owl” Tetradrachm
I bought this coin with the intention of cleaning the blackish-brown deposits on the obverse, which I had identified as horn silver. From judging the wear and surface quality, I believed the coin to be of great condition and a good price at which I had won it. While I’m not unhappy with the cleaning, I did learn a valuable lesson from it: significant surface issues can be present under horn silver even if not present elsewhere. After the horn silver was removed, it was clear that it had already “eaten” away at the surface layer of the silver and left some unsightly areas. Still, I find the coin much improved after cleaning compared to before it.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
- Tombow Mono Zero Eraser – 2.3mm
Methods:
Same thiosulfate treatment as with earlier coins. The thiosulfate worked quickly and the horn silver was not difficult to remove. I even noticed the horn silver would start to dissolve once covered by the solution without any mechanical intervention, though I lightly used toothpicks to help it along. After treatment, this coin had a slight yellowy-brown colour due to the thiosulfate and required some cleaning with the eraser to restore the silver colour of the surface.
5. Thasos “Satyr” Stater
As with the previous coin, I also bought this coin with the intention of cleaning it, believing it to be a fairly respectable example of its type underneath all the gunk and deposits. I figured some of the black deposits would be removed with thiosulfate solution, while the lighter brown deposits may just required mechanical cleaning with a toothpick. In practice, things turned out much more difficult and as can be seen from the “after” photo, not all of the deposits were removed. This coin also saw me try a new tool for the first time: an ultrasonic cleaner. My take-aways from the ultrasonic cleaner were threefold: (1) it can be effective at removing some hard deposits; (2) it can more clearly reveal porous areas of the surface as it cleans all the debris out of them; and, (3) it can loosen weak parts of the surface and remove them.
For these three reasons, I believe the use of an ultrasonic cleaner should be reserved for truly difficult coins to clean and it should not be used on coins with weak surfaces, such as those with delamination, chipping, or porosity. I would also not risk using it on a coin with lustrous surfaces as it may dull them.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
- Tombow Mono Zero Eraser – 2.3mm
- Ultrasonic cleaner
Methods:
Same thiosulfate treatment as with earlier coins but progress was slow and tedious. Most of the work was done with toothpick cleaning and the ultrasonic cleaner. I bought the ultrasonic cleaner without knowing for sure the effect it would have or if it would damage the coin. I started by submerging the coin in the water and detergent solution and running the ultrasonic cleaner for up to 2 minutes at a time. Moving the coin around in the cleaner so that it is over areas of more intense vibration seems to help somewhat. After treatment, this coin had a slight yellowy-brown colour due to the thiosulfate and required some cleaning with the eraser to restore the silver colour of the surface.
6. Alexander III “Arados” Tetradrachm
Another coin I bought with the intention of cleaning it up to improve it. I felt confident that the black deposits and staining on the obverse could likely be removed with a thiosulfate solution and in practice this did work. Through careful application of the solution, I was able to preserve most of the toning around the effected areas. One consequence of the cleaning is that the delamination on the portrait of Herakles is more noticeable but overall I consider the coin to have been improved significantly.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
Methods:
Same thiosulfate treatment as with earlier coins. The thiosulfate worked quickly and the black deposits were easy to remove. I was careful to apply the solution only to the effected areas to try and preserve the toning in other parts of the obverse. After cleaning in the solution, I found that the coin hadn’t taken the normal yellowy-brown toning that usually appears after treatment so it did not require cleaning with an eraser.
7. Lysimachos “Lampsakos” Tetradrachm
This coin is perhaps the one that I have gambled the most on when it comes to cleaning. Not only was it one of the most expensive coins I’ve bought, it was also one that I was the least certain of being able to clean, and one that needed cleaning the most. The strange pale brown, green, and yellow, deposits were unusual to me at the time. They seem to coat the coin without being built up into large lumps like I was used to from other coins. I did not expect thiosulfate would help me here but as I could see signs of lustrous surfaces under the deposits, and the style in general was excellent, I thought this coin was worth taking a shot on.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
Methods:
I had the most success with mechanical cleaning using a toothpick, slowly chipping away at the deposits bit-by-bit. I started by soaking the coin in acetone for 15 minutes, though it’s not clear if this had much of an effect on the later cleaning. I started by using an eye dropping to coat the surface of the coin in distilled water to help suspend the small particles of the deposit that were lifting off the surface with the aid of the toothpick. This helped to ensure I wasn’t rubbing these deposits back into the surface with the toothpick and also made it easier for me to see what I was doing. I tried a thiosulfate solution once I had the majority of the deposits removed to see if it would help with the last remaining bits but it had little to no effect. I wasn’t able to remove some of the deposits that are more firmly seated in small pockets and depressions on the surfaces but overall was very happy with how the coin turned out.
8. Alexander I Balas “Antioch” Tetradrachm
I didn’t expect I would need to clean this coin when I first purchased it, however once I had it in-hand I felt that it could benefit from a light cleaning. It appeared as if it had a kind of “find patina” on it, where the original earthen deposits hadn’t been fully cleaned off but were only lightly coating the coin. I saw signs of better surfaces underneath this “patina” so decided to try and remove it to reveal the true surface of the coin.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- Tombow Mono Zero Eraser – 2.3mm
- Toothbrush
Methods:
No thiosulfate was required for this cleaning job, most of the work was done using toothpicks, a toothbrush, and the Mono Zero eraser. Not all of the patina would come off with the help of acetone so the eraser was employed to finish the job. I tend to only use the eraser once it’s clear there are no deposits left on the surface, only “toning”. You do not want to be rubbing any foreign material into the surfaces of the coin. If you’re unsure, it’s best to start on the edge of the coin to see how it responds, or even rub a part of the surface with your fingers. If it comes off, it’s likely something that can be safely cleaned using the eraser.
9. Alexander III “Babylon” Tetradrachm
I purchased this coin some months after having cleaned the Lysimachos tetradrachm. To me, it seemed like a similar type of deposit and thus require similar cleaning methods. I also thought there was perhaps some horn silver or otherwise a black-ish deposit that may respond to thiosulfate. Ultimately, I was able to remove most the deposits with the help of the usual methods and the ultrasonic cleaner. I found the ultrasonic cleaner to be incredibly effective but almost too effective. After I had removed most of the deposits and horn silver, I used the ultrasonic cleaner just to clean up the last parts. However, I found that immediately after being turned on, a big black cloud of particles emerged from all around the coin in the ultrasonic bath. It turned out that a lot of the horn silver was “hiding” in the porous surface, where a toothpick can’t get to it. The ultrasonic cleaner shook this horn silver out and revealed the true extent of the porosity. This is perhaps a case where the ultrasonic cleaner did too much and the porosity was less noticeable when it was filled with deposits but I am still pleased with how the coin cleaned up.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
- Tombow Mono Zero Eraser – 2.3mm
- Ultrasonic cleaner
Methods:
Bathed in a thiosulfate solution and then cleaned with toothpicks and cotton swabs. For the last bit of cleaning, I ran it through one 2 minute ultrasonic cleaning cycle, where it proceeded to remove a large amount of horn silver or other deposits from every nook and cranny. This revealed the extent of the surface porosity to a degree that was not visible beforehand. I finished off the cleaning process with the Mono Zero eraser to remove the yellow tone of the thiosulfate solution.
10. Paphos “Bull/Eagle” Stater
This coin only required a small amount of cleaning to remove some of the black-ish deposits on the obverse and reverse and some of the yellowy-green deposits on the reverse. I mainly wanted to remove the black-ish deposits on the obverse because they contrasted with some light surface scratches and drew attention to them. I was very happy with the coin even without the cleaning but I saw it as fairly low-risk and could improve the coin just enough.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
Methods:
The usual cleaning methods used with the thiosulfate solution, namely toothpicks and cotton swabs after soaking areas of the coin for up to several minutes at a time. The yellowy-green deposits on the reverse came off with just a light nudge from the toothpick and didn’t require soaking beforehand.
11. Antiochos I “Seleucia” Tetradrachm
Similar to the Alexander I Balas tetradrachm, I mainly wanted to tidy up the surfaces of the coin as they were covered in a light earthen deposit and perhaps some darker areas of silver oxide. The cleaning would help bring the focus back to the features of the coin and allow for the surface to develop a more consistent and attractive toning. In the mean time, you do end up with brighter surfaces than you ideally want but over time the surface should tone nicely. This type of cleaning is what I would consider “optional” and down to personal preference. The coin would’ve been just fine as it was but when possible, and when the risk is low, I do sometimes try to improve a coin with a little cleaning.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- Tombow Mono Zero Eraser – 2.3mm
Methods:
Some gentle cleaning with toothpicks and cotton swabs following an acetone bath. Once I was left with just the surface coating of what I believed to be silver oxide, I used the Mono Zero eraser to clean this off and some of the areas with a thicker layer of toning.
12. Mark Antony “Ephesus” Cistophorus
This cistophorus has several types of deposits and numerous surface scratches, likely from both cleaning and some that naturally occurred during its use in circulation 2,000 years ago. My main goals were to remove as much of the deposits as possible and clean the surface so as to make the surface scratches less noticeable. I don’t do anything to remove the scratches, such as polishing, I only try to remove anything providing contrast, such as some toning that was scratched over. When the toning is removed, the contrast is lessened so it’s harder to notice the scratches and when the toning re-forms, it will cover them even further.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
- Tombow Mono Zero Eraser – 2.3mm
Methods:
I had limited success with both the thiosulfate solution and mechanical cleaning methods. Some gentle cleaning with toothpicks and cotton swabs followed an acetone bath, and after that I tried the thiosulfate. As can be seen, many deposits were removed or reduced in size, but many still remain and appear to be extremely well fixed to the coin. I believe one would need to resort to diamond-tipped tools to break them up but in this case I believe it wouldn’t be worth the effort given the risk of scratching the coin further.
13. Athens “Owl” Tetradrachm
Similar to the other “Owl” tetradrachm I cleaned earlier, this one also had some thick-ish blobs of what appeared to be horn silver on the portait of Athena. I had learned my lesson from this previous cleaning attempt and knew the risks that removing the horn silver would reveal the surface damage underneath. In this case, since this was a fairly uncommon type (Starr V.B.) relative to the more common “Mass Issue” tetradrachms, I decided it was worth it even if the horn silver had caused lasting damage. Aside from removing the horn silver, the coin’s surface was slightly cloudy and dull with some thick but spotty areas of toning and oxidation. I noticed the surface underneath appeared to be quite good and removing this toning/oxidation layer would better reveal the surface quality of the coin.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
- Tombow Mono Zero Eraser – 2.3mm
Methods:
As expected, these blobs of horn silver were covering up the damage they had caused to the surface and removing them revealed the top layer of silver had been “eaten” away in parts. Overall, the extent of the damage to the surface was not too bad and I left some spots with a small amount of horn silver remaining rather than cleaning them completely. Following the thiosulfate treatment, the Mono Zero eraser was used to remove the usual left-over toning and this also saw the remaining surfaces cleaned up.
14. Tarsos “Datames” Stater
The staters of Tarsos issued by the Satrap Datames tend to have a crenellated border on the obverse, though to depict the famous Walls of Tarsos. These crenellations seem to attract horn silver, or at least hide it sufficiently that it gets missed frequently when cleaned. My example had this typical horn silver hiding in the crenellations and I aimed to see whether it could be removed, as I thought it otherwise detratced significantly from these types, though it wasn’t too bad on my own example.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- 10% Ammonium Thiosulfate / distilled water solution
- Tombow Mono Zero Eraser – 2.3mm
Methods:
Treatment using the thiosulfate solution cleaned up the horn silver hiding in the crenellated border relatively easily. This type of horn silver was perhaps “crystallised”, and resembled silver itself rather than a black-ish deposit. Surprisingly, these large chunks of horn silver would come right off the surface with the aid of a toothpick, while other smaller deposits of horn silver on the figure of Baal or Ana and Datames on the reverse, remained and were more difficult to remove.
15. Alexander III “Rhodes” Tetradrachm
This Alexandrine tetradrachm of Rhodes had an unusual yellow and brown staining to the surfaces that made them appear cloudy in parts. In general, the staining looked inconsistent and a bit unsightly and I thought it relatively low risk to attempt to remove it. This same staining can be found on other Hellenistic tetradrachms that were sold by the same auction house, at around the same time, under the same NGC batch number. This indicated the staining was from some unique condition that the hoard of coins was exposed to whilst buried and I expected it shouldn’t be too troublesome to remove.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- Tombow Mono Zero Eraser – 2.3mm
Methods:
Perhaps unsurprisingly, acetone and other solvents were of no use in removing the staining. While thiosulfate may have had some success, I didn’t think it would be necessary and decided to jump straight to cleaning the surface with the Mono Zero eraser. The staining is more similar to toning than to a deposit, so removing the staining using friction should be relatively safe. The eraser had no trouble and most of the staining was removed with ease. I did not try to clean the entire surfaces of the coin, rather just the main areas, even if that means some small amounts of staining remained in other parts.
16. Philip III “Babylon” Tetradrachm
Rarely do you see a coin with such a thick and pleasant “find patina” as this coin. It had a lovely dark tone across nearly all of the surfaces, except in a few places where it was interrupted by ugly bright spots shining through. It was for this reason that I decided to clean the coin of the patina, something I wouldn’t do otherwise. It was relatively simple to clean, requiring only a soak in Sodium Thiosulfate.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- Tombow Mono Zero Eraser – 2.3mm
Methods:
A quick bath in sodium thiosulfate to remove the patina with the aid of cotton swaps and toothpicks for the hard-to-reach areas. A quick pass with the Tombow eraser was needed to remove the toning left over from the Sodium Thiosulfate.
17. Seleukos II “Antioch” Tetradrachm
This tetradrachm obviously has been cleaned once before, and quite poorly. In the reverse between the devices are large “swirls” through the blank gunk. At first they appear to be scratches but upon inspection under my microscope, I realised that they were likely just marks left in the toning/deposits. As I was planning to clean the brown stuff from the obverse anyway, I also tackled the reverse and managed to remove most of the swirling marks from the previous person’s cleaning attempt. The flan of this coin is a bit unusual on the reverse in that it has thick vertical striations throughout most of the surfaces. I’m unsure exactly what caused them but since they’re raised and not depressed, they’re not cleaning marks. The could perhaps be tool marks from the die itself where the engraver may have tried to smooth out a roughened die surface and in the process left some markings on the die.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- Tombow Mono Zero Eraser – 2.3mm
Methods:
Same “thiosulfate” procedure as discussed many times already.
18. Alexander III “Coele-Syria” Tetradrachm
The auction photos for this coin were perhaps a bit deceiving in that while it was clear the coin’s surfaces were covered in hornsilver, the hornsilver looked to be mostly “sitting” on top of the surfaces and underneath in parts the surfaces were quite good. So I was confident going into this cleaning job that the hornsilver would come away quickly with thiosulfate treatment. Instead, this ended up being one of the more unusual cleaning jobs I’ve yet attempted. Initially, thiosulfate didn’t remove any hornsilver, nor did it darken it like it normally would. I noticed that the toothpick wasn’t dislodging the hornsilver either, rather it was carving it, leaving deep marks the width of the toothpick’s point. This worried me at first as I had never seen hornsilver respond this way and thought that perhaps it had fused too solidly with the coin’s actual surfaces. I was leaving deep toothpick lines all over the surface and none of the hornsilver was actually coming away.
In the end I did something that I don’t normally do and left the coin to soak in a high concentration (30%) thiosulfate solution overnight. Typically I would treat a coin with hornsilver for no more than 5 minutes at a time so an 8 hour treatment was quite significant. Thankfully, the hornsilver did start to respond and in the morning it had blackened slightly. A toothpick was then able to dislodge it from the surfaces and I could see that I hadn’t scratched the surfaces with the toothpick at all, the only scratches were in the hornsilver itself. The downside of the long treatment is that the thiosulfate toned every nook and cranny of the surfaces, including down in all the porous areas that had been affected by the hornsilver. What this meant is that while I could remove the dark toning from the top surface, the porous parts of the surface remained dark and now easily draw the eye’s attention to the porosity of the coin.
That being said, removing the hornsilver improved the coin in many respects, revealing significant details in the Herakles portrait as well as the Zeus figure, legend, and boar’s head. So the treatment may not have gone to plan but the end results were satisfying nonetheless. While some may prefer the look of the coin pre-cleaning, it’s difficult to convey just how bad it looked in the hand.
Equipment:
- Cotton swabs
- Toothpicks
- Acetone
- Tombow Mono Zero Eraser – 2.3mm
Methods:
Long soaks in sodium thiosulfate followed by cleaning with a toothpick and cleaning the toning from the surfaces with the Tombow eraser.
19. Alexander III “Tarsos” Tetradrachm
A lovely tetradrachm from Tarsos with a full-dotted border on the reverse showing the full extent of the die that struck the coin. The only improvement that could be made is to clean the deposits obscuring part of the dotted border, legend, and fields. An easy job, I thought once again, yet it was not to be. The deposits responded neither to thiosulfate or citrus acid in any meaningful way. Some was cleared through this usual method combined with toothpicks but not enough and repeated treatments did little. I did however suspect that the deposits were harder than the silver on which they were attached. This is because the toothpick started making tiny hairline scratches into the surfaces on the rightside of the reverse outside of the border. Likely some deposits had become embedded into the toothpicks and scratches the silver surfaces slightly. This is something I could only notice when using my microscope while cleaning so this is something to keep in mind when using toothpicks. It may appear that you’re not doing any damage, but you can be making miniscule scratches if the deposits are harder than the silver.
In the end, I had to resort to careful mechanical cleaning to dislodge most of the deposits. Thankfully I largely avoided damaging the surfaces any further than the toothpicks had and all of the large cleaning scratches that are visible are from the previous person who cleaned the coin and can be found in the “before” photo.
Equipment:
- Cotton swabs
- Toothpicks
- Tombow Mono Zero Eraser – 2.3mm
- 20-40x Stereo Microscope
Methods:
Mechanical cleaning with a cleaning pencil and diamond-tipped pin needles. Tireless and repetitive work but it was the only thing that would work after my usual treatments of thiosulfate and citric acid had done little to remove the deposits.