I've got a 1981 100 Peso coin from Chile. When I first looked at it I thought, wow this is very chocolatey, like literally I wanted to take a bite So I was already slightly suspicious of it's appearance but didn't pay much attention as I continued my routine which is to take coins like this (circulated/unknown history) and give it an acetone soak. I usually just do 5 or 10 minutes in jar #1, a few minutes in #2, and then a final swish in the cleanest jar. To my surprise it revealed what at first looked to be white chalky stuff on the coin especially against the devices. I was like that's odd, never had an issue with acetone doing that before. So I thought let's poke it with a toothpick. It seems to be waxy. I know this isn't an uncommon practice, especially "back in the day" so I'm not real surprised. I'm not 100% sure that's what it is as I've never seen it before and I'm not even sure what they would have used. Does this sound like what I have? I dont' have pics yet, maybe later but I actually put it back in the acetone to soak more hoping it would loosen up the wax, but that leads me to my next question of will that work? Probably depends on the type of wax I would suppose?
It might be the remnants of Deller's Darkener. It's a chemical that was used to recolor cleaned copper coins to a "natural" look. Often after a period of time a coin that has had this chemical applied will begin to develop a white substance around lettering and other design elements. When you soaked it in acetone it could have possibly revealed this or sped up its development.
Interesting, well we'll see what happens. I'm gonna leave it in there for a while. This isn't a valuable coin by any means so it's a good experiment
After the initial 5 minute soak earlier and before I put this back in to soak in it's own new jar of acetone I snapped a couple of pictures. There was no sign of what appears to be white waxy residue prior to the acetone rinse. Again, this isn't a coin with much value but it's a good experiment and I rather like the deep brown coloring (maybe it'll fade without the wax)
@Jeepfreak81 When you poke at the white substance, does it sort of just flake away? Or is it solid and firm.
Let the coin soak for a few hours in the acetone for the first bath and throw out that acetone. Don't let the coin dry and soak a few more hours in the second bath and throw out that acetone. Rinse the coin with water and swish the coin in acetone. At that point the acetone is not going to help any more.
no it's not very firm, kinda squishy and easily pushed around @ldhair thanks for the tip, that's sort of what the plan was. I wasn't sure if I was even on the right track or if this is a job for xylene or just a big waste of time. LOL, oh well - I'm not out anything to try really.
After a couple hours in an acetone soak, I removed the coin and rolled the surface with a q-tip and placed it back in some fresh acetone for a few more hours. Just before bed last night I removed it again and rolled it with a q-tip once more. It's a noticeable improvement, a quick look with a loupe and I can for sure still see the "stuff" especially in the smaller details like the dentils but a large percentage of it is gone or reduced as to not be noticeable. I'll take a couple of updated photos this evening and share. I think I'll also leave this one out of a flip for now and try xylene to see what, if anything, that does. The acetone seems to soften the waxy goop that's on it considerably but you still have to use mechanical means to remove it from the coin. Rolling a q-tip got alot of it, I did use a toothpick in a few stubborn areas which I wouldn't have done on a MS coin but this one, meh.
Really? I would think that would be much more soluble and gritty. This definitely seems waxy and somewhat stubborn. But I've not encountered this before. I'm looking into xylene now as well, may as well experiment with this low value coin.
I had a friend who was nuts about cleaning coins with baking soda. the stuff would get wedged in various spots and then turn into concrete that would take hours of soaking to lossen.
Ok all, I'm back with an update - and pictures. First - *full disclosure* - between the first pictures and second pictures I got some new lights setup for taking pictures. I tried to get the temp and everything as equal as I could. I should have taken pictures before I tore down my old setup. Ok now, just to recap. I got the coin, it was very "chocolately" and I was a bit sus of the surface. Just seemed a bit off but I didn't investigate closely, I just dropped it into the acetone bath to clean off loose gunk before putting in a 2x2. So after about 5-10 minutes total, I ended up with what you see in the top pair of images below. Looks to be a waxy residue that had been applied. So, then I got a different jar put in some fresh acetone and let it soak about 2-3 hours. I removed the coin and rolled a q-tip over the surface numerous times, redipping it in the acetone to try and keep it wet. I also used a toothpick to get some tough spots. Then it went into the jar with FRESH acetone for another 1-2 hours. Again I rolled a q-tip over the surfaces, re-wetting it numerous times and going through a handful of q-tips. Then I gave it a swish rinse in a clean jar of acetone. And now I have what you see in the bottom 2 images below. Conclusion - I removed a large amount of the gunk and in my humble opinion greatly improved the look of the coin from the previous images. It's not as deep and chocolately anymore but it looks more natural. That being said - I didn't get it all. I probably could if I repeated the process a few times and took more care to get it all. Side note - it appears to also have some spots of Verdigris? I don't think it's PVC residue or it would have come off in the acetone baths. So there you have it - feel free to discuss, ask questions, tell me I ruined it, applaud my efforts, pat me on the back, or ignore me.
Nice job! I don't see any scratches so I would say that this was a successful conservation. You might want to brush it with some light oil.
Thanks! Brush it with oil you say? Like Olive oil? I've seen that mentioned before but thought it was more for really old copper.
Mineral oil. Does wonderful things "visually" for old copper and bronze. I wouldn't necessarily use it on a coin (especially US), but it really does improve the appearance of bronze medals. And, I believe, it does offer some protection from the dreaded "green spot disease," which after all, is initiated by moisture / water. The oil protects against that. Z
I’ll throw this out there. Take it for what it’s worth….. Once upon a time shellack was used as a durable coating. Still is used on some wood projects. I will use shellack when I am repairing old wood pieces occasionally. And the more I read this, the more this sounds like an old coating of shellack to me. Denatured alcohol is what cuts shellack, though I have no idea what it may do to a coin surface. Just a thought from the cheap seats.
Shellac in my experience hardens (and you're right it is a great durable coating). Maybe over time it can soften up again? Whatever this was/is will probably remain a mystery but it's looking much better and it's nothing special for a coin, just a neat piece that will go in a 2x2.
