A few months ago I bought a coin that looked like it might have some active BD going on. The coin pretty clearly had been a victim of bronze disease, and while most of the stuff had been removed there were still pockets and areas of green on both the obverse and reverse. Here are the dealer photos: The coin was from a dealer I trust and the price was right, so I took the challenge and bought the coin. As you can see, despite the corrosion the coin still retains some very nice details. I like these DIVVS AVGVSTVS coins, but a really nice example doesn't come cheap. When the coin arrived, I took it out of the flip and scraped the green areas with a wooden toothpick. Yep, the powdery green stuff came off. Great. I did some research and decided to do some long-term soaking. I ordered a bag of sodium sesquicarbonate and mixed it in a covered bowl with distilled water for about a 5% solution. I changed the water about every week, when I could see the water getting a very slight bluish tint. In between changes, I sometimes scraped the BD with a toothpick or a small nylon brush. I probably erred on the side of caution - letting the coin soak for a couple months - but I wanted to be sure every bit of that cursed corrosion was gone before I stopped. I could see progress as the green slowly disappeared. Finally, there was only a couple tiny dots left, which turned out to be some hard deposits. The corrosion was all gone! Unfortunately, the long soak had adversely affected the coin's surface, resulting in a hideously flat and mottled appearance. I didn't get any pictures of the coin in this state but it was so bad I thought it might be ruined, after all. The only thing I could think of to salvage the coin and bring it back to a semi-natural appearance was to give it an artificial patina - something I'm generally not in favor of but justified in this case, I think. I mixed some liver of sulphur in some warm water and dunked the coin for a minute or two. Parts of the coin darkened quickly, but other spots stayed a light-ish gray color. Disappointing. I took it out, rinsed it, and tried again. This time, the entire surface darkened nicely and evenly. I removed the coin, rinsed it in a baking soda solution, and then under running water I gently cleaned the surface, gradually lightening the coin's high surfaces. After this was accomplished to my satisfaction, I thoroughly dried the coin and applied a thin coating of Rennaissance Wax to seal the surface and protect the coin from future corrosion. Whew! Project complete! Poor old Augustus has been through a lot, but I am very pleased (and more than a little relieved!) with how it came out in the end. I can enjoy it now! I'm a little disappointed about having to give it an artificial patina, but hey, better that than to be relegated to the junk box, right? And here is the final result: Feel free to share your thoughts, good or bad!
