Hello everyone, I decided to purchase this Roman Republic Semuncia on ebay because of how low it was priced and how clean it was overall. I have hope that I can remove some of the encrustation on the obverse and make it a truly stunning example, but I need help. I think I will have to use some sort of abrasive tools to effectively remove the green encrustation, but I don't want to ruin this coin. Does anyone have any recommendations or ideas on how I should procede? Thanks everyone!
I break the surface on the crust very lightly and not very deep. Then soak for several days in 40 volume peroxide. This is usually only available at beauty supply stores. Then between soaks I remove it a little at a time. I change the peroxide every couple of days. It takes a long time.
If you cover the container that the peroxide is in don't cover tight. The peroxide puts off a gas that will build up and blow the top off. When you put the coin in you can see the bubbles starting to remove impurities. And, get a good photo of a clean, representative coin to help guide you.
What great detail! Congrats. I would not attempt to alter the coin and recommend you leave that little beauty as is. It's not going to look much better, but can look much worse. It would be very as to, as you say, ruin the coin.
The corrosion likely contains metal from the surface of the coin that has reacted with chemicals in the soil that it was buried in. It's not just something built up on the surface of your coin; it's part of your coin. If you remove it, you will uncover a rough, pitted surface. It might look better without the corrosion, but it might look worse. Hard to say. Are you willing to sacrifice your coin in the name of science?
I agree with gsimonel. There are corrosion products that build up on a relatively stable surface near to the original surface, and can therefore often be removed safely. And then there are the large blobs/blisters of corrosion like on the obverse of yours which represents a deep corrosion transformation of that part of the coin. It is not very likely that there is anything stale under there. SC
I have to concur, if thats in the metal and you try to clean, its going to get ugly real quick. If your really itching to see just use a bamboo skewer on a small section just to see if anything gives to tell you. Honestly though from someone who's had to learn the expensive and sometimes heartbreaking hard way, I would leave it as is. Its already awesome
Not bad but still prehistoric as compared to my proprietary cleaning method on copper, brass & bronze. P.S. Looking for a new challenge. This qualifies. Nutmeg Numismatics. Current record 2 Wins/0 Losses. <BG> Send me a private PM if in the U.S.. JJ John Lorenzo Numismatist
How did you ever get started using peroxide? Does anybody else use this? Hydrogen peroxide is an oxidizer and I can't see what good it would do on coins. The bubbles you see escaping is oxygen from the hydrogen peroxide whose decomposition is catalyzed by the rough surfaces. Peroxide would remove organic debris pretty well, but I'm not sure what it would do for most inorganics and dirt beyond what water would do.
This makes it a little easier to see. If anything, I would heat up some water to boiling and soak it for a day. Repeat 2-3 times and then try brushing with a toothbrush. See what that does first.
Thats about all I would do maybe boil in wash and baking soda mix but even thats a bit much. I think it looks great now. I wouldn't dig in that either. Just my opinion.
There is no sure thing in cleaning. I heard it from someone some time back. What it seems to do for me is loosen build up. It doesn't remove or dissolve. I also use acetone and distilled water. I understand the bubbles, but, there seems to be a residue in the bowl when I rinse. All I can say is that one or the other of the three solutions, along with time, seem to do the trick.
I used it for raw metal detecting finds, to remove the dirt. Stopped using it as results were unfavorable. Bronze will get pitted and worn out quickly, silver of good quality may have some benefits from this treatment (but other treatments are preferable). For this specific coin, I would not advice a chemical treatment and echo what's said by others: the underlying material may be rough already. Soaking it in distilled water (not just tap water; distilled water will 'absorb' the deposits while chlorinated tap water might harm the coin) for a prolonged period in combination with gentle mechanical cleaning (e.g. rubbing or using a toothbrush) will likely improve the coin somewhat. Also, make sure not to seal the coin after cleaning (e.g. in a 2 by 2 or slab): the humidity might result in bronze disease.
I understand that there are times that nothing will work. I will try several things to loosen the crud. If it won't give and a hint of bronze or red starts to show, it is time to stop. My method only applies to helping stubborn material give. Following is an example of one that could never be cleaned without serious damage. A hint of red showed u p.
