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Message:: [QUOTE="Silverlock, post: 3620524, member: 98181"]This is a long post, I hope you’ll find helpful. When a Ptolemy AE47 87 gram “hockey puck” in good condition appeared on VCoins earlier this year at a very good price, I jumped on it. [ATTACH=full]970461[/ATTACH] [ATTACH=full]970460[/ATTACH] Ptolemy III Octobol Alexandria 47 mm 87.47 gms Obv. Head of Zeus, right Rev. Eagle standing, right, club before Ref. Svoronos 446 Isn’t that a beauty? I won’t mention the dealer or show the VCoins photos because I don’t want to name and shame: I’m sure the dealer would have accepted a return, but I never asked for one. What apparently happened on the long trip across the ocean, and possibly even longer trip through customs, was that bronze disease erupted. Rather than return it and risk it being destroyed, I decided to try my hand at saving the coin. It turned into quite an adventure. The first step was to clean the coin. I gave it an acetone wash to remove hand oils. This should have been a trivial step, but what happened was a lot of putty-type filler softened and then rubbed off when drying the coin. Someone had applied what looked like cosmetic foundation to the surface of coin to hide casting pits and other defects, including additional areas of active bronze disease. Maybe I should name and shame. Just kidding. The next step was a soft bristled toothbrush to remove the loose bronze powder. It came off easily and there was a lot of it. A lot of dirt and putty came off as well. Whoever prepped this coin didn’t care about it at all. Next step was a bamboo skewer to remove any remaining visible bronze disease. I was in for another surprise when the casting pits visible on the obverse — see photo — turned out to be active bronze disease reservoirs. Someone had dyed those areas a dark brown, but beneath the dye was active bronze disease that had etched out a larger pit than it appeared. With the help of a microscope, I scraped those areas clean. At this point I was having second thoughts about not returning the coin. But I carried on. It was now ready to soak in sodium sesquicarbonate. I bought the powder from Amazon, along with a graduated liter bottle and a small mason jar. I mixed a 5% solution, by weighing 50 g and adding it to 1000 ml of water. Easy peasy. Go metric system. Taking care not to get hand oil on the coin, I wiped it with the fluid on a q-tip to prevent bubbles and dropped it and watched intently, expecting it to at least fizz or something. Nothing. Darn. I planned to let it soak two weeks, but when I checked it an hour later, the solution was a dark blue. The British Museum changes the solution when it turns blue, so I changed it. I changed it eight more times that day. The next morning the solution was blue, but interestingly no bluer than it was after an hour or two the day before. I took this to mean the reaction was complete, and leaving it sitting in what was essentially blue water wouldn’t do anything good for the coin. I tested this later, but it turns this assumption was basically correct. I changed it every few hours for the next couple weeks, before it finally settled down to once a day. It stayed at once a day for the next three months. Aside from burning through a ton of sodium sesquicarbonate, not much seemed to be happening as far as the bronze disease was concerned. The coin was still largely light green on both sides. I’d read that this process would strip patina, but that was only somewhat true. Certainly the surfaces had changed color, darkened mostly, and the white and orange had dissolved away, but as far as the harder dark brown patina was concerned there didn’t seem to be much change. Fast forward three months of soaking, eventually reaching the point where I could change the solution every two weeks, and by then much of the light green was gone. At this point I forgot about the coin, and it sat for over a month in solution. Something fascinating happened, and I wish I’d taken a photo of it. Rising above the pits where bronze disease had been most active, were plumes of darker fluid in the solution. They looked like little blue tinted tornados rising from the pits. Apparently the disease was still active in there, and the plumes showed there was no real mixing taking place. Most of the fluid was contributing nothing. I dug the pits out again with a bamboo skewer, and put it back to soak. A month later the solution had not changed color, and all I had done was swish it around occasionally to get fresh fluid in contact with the coin. I took the coin out, gave it a distilled water rinse and soak, and left it to dry. After two weeks it hasn’t changed. Here’s the final result: [ATTACH=full]970458[/ATTACH] [ATTACH=full]970459[/ATTACH] It still isn’t a beauty, but at least it isn’t dissolving away anymore. The light green areas that look bronze diseasy are actual quite hard, so I don’t expect the disease to erupt from them. If it does, I’ll repeat the process again. The best part for me is the cleaning revealed that someone in ancient times decided Zeus looked puffy cheeked, and graffitied lines to make it look like he was blowing. I just love that. Banksy would be proud. People haven’t changed much in 2000 years, have they?[/QUOTE]

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