Tarnish on brass Casascius coins, what to do?

[rbdrbd]

Hi, I have been looking at a few 2011 brass Casascius coins that appear to have some tarnish on them but otherwise look to be in pretty good shape. Is it possible to use a brass cleaner (like Weiman Brass polish, or Brasso metal polish) on the front of the coin at least (not anywhere near the hologram) to clean them up, or is this just a Bad Idea that will cause issues?

Are the brass coins (and silver coins for that matter) prone to tarnish in general, if not kept in an airtight storage container?

Thanks in advance for all guidance here!

[The Sceptical Chymist]

Coin collectors will always tell you never to clean coins, but it's your decision.  Just be aware that if you end up selling your coin to a collector, you should disclose that you cleaned it and that having done so might dissuade some of them from buying it.  

As far as the cleaning goes, I've cleaned some coins before and sometimes soap and water does the trick.  If not, some brass polish will definitely work.  You can get some of that at your local hardware store or maybe a Walmart or similar big-box store.  But I probably wouldn't do anything.  Do you have a picture of it by any chance?

Are the brass coins (and silver coins for that matter) prone to tarnish in general, if not kept in an airtight storage container?

I don't have any brass coins, but I have a brass pharmaceutical weight (1kg) that I cannot keep from tarnishing.  I've polished it, but even then I can't remove all of the spots and I've stopped trying.  I've always thought brass was more resistant to oxidation than silver, but apparently not in my house.

[henkcryptotank]

RULE #1 OF COIN CLUB IS...

Greets Hank

[rbdrbd]

Thanks guys. I will resist all urges to "clean" my coins. 

[SaltySpitoon]

I've always wondered about the coin cleaning thing for non precious metals. As far as I know, the reason people tell you not to clean coins is that chemical and abrasive cleaning methods can damage the mint finish (gold/silver). I was under the impression that the reason you don't clean old non precious metal coins is because they are more fragile due to their age, and you can damage the detailing.

I'd get a second opinion, but I don't know that cleaning a brass coin from 2011 falls under the same no clean rules as silver/gold or non precious metal coins from the 1800s or earlier. You can tell if an old coin has been cleaned. Not sure if thats the same in this case or not.

[krogothmanhattan]

This should give you some insight on why you should not clean coins!

https://aboutredlands.com/articles/this-is-why-you-shouldnt-clean-valuable-coins

[El duderino_]

Rule #1  NEVER CLEAN A COIN

I have only very recently started collecting BTC-related stuff, but I did collect some other things... much in the movie things and I will thread my coins or other BTC stuff same wise, never unpack the item ....

As I also have a few motocycles in collection ( gonna stop with that hobby to much work around) but a few very old ones I had, completely rusted up and shit were worth much more then totally cleaned up

ps maybe just open items to see they are in there... but when possible just let them be sealed

[tweetious]

If we use a small amount of vinegar and softly rub the coin with a soft cloth, will the mint finish be damaged? Does vinegar also classify as an abrasive cleaning method, since it can also harm the coin? (alternatively, if we just put the coin for a couple of minutes in a small cup of vinegar without rub it with a cloth?)

[Ticked]

just put the coin for a couple of minutes in a small cup of vinegar without rub it with a cloth?)

The HOLO, would someone please think of the holo?!

Honestly, I have no idea, but i'm scared of what this might do to a hologram.

[tweetious]

just put the coin for a couple of minutes in a small cup of vinegar without rub it with a cloth?)

The HOLO, would someone please think of the holo?!

Honestly, I have no idea, but i'm scared of what this might do to a hologram.

obviously for those coins WITHOUT a holo (for the sink method) 

[gentlemand]

Are the brass coins (and silver coins for that matter) prone to tarnish in general, if not kept in an airtight storage container?

The Casascius Bitcoin Bowl silver coins were sold with a case that has left plenty of marks. Had I know that would happen I would certainly have put it in a proper container. The other silver coins I have that came in proper containers are unmarked.

Personally I don't get the taboo about coin cleaning, but if you ever plan to resell then I guess that anality needs to be respected.

[dazedfool]

just put the coin for a couple of minutes in a small cup of vinegar without rub it with a cloth?)

The HOLO, would someone please think of the holo?!

Honestly, I have no idea, but i'm scared of what this might do to a hologram.

obviously for those coins WITHOUT a holo (for the sink method) 

acetone has a similar effect. mildly pulls skin oil like fingerprints off without damaging the patina

acetone on a cas brass 2011 error will DISSOLVE THE INK ADDRESS BITS ON THE HOLO

don't ask me know I know that.... 

[krogothmanhattan]

just put the coin for a couple of minutes in a small cup of vinegar without rub it with a cloth?)

The HOLO, would someone please think of the holo?!

Honestly, I have no idea, but i'm scared of what this might do to a hologram.

AYe the HOLO! Great point!. We are unique in our hobby has a Holo with a paper underneath! That's a major risk!

So just leave well enough alone! I would not buy a cleaned coin PERIOD!

[Lesbian Cow]

Conservation is OK, cleaning is not.  What's the difference, you ask.  Conservation is done so well that a grader can not tell the coin has been cleaned.  The "cleaned" coin is considered "market acceptable".

Conservation is done by professionals with proprietary solutions they have developed over years.  The process is called dipping.  The best in the business are very expensive and sought after.  Some of them are also Dealers and buy problem coins, conserve, get graded and maybe profit.  PCGS and NGC also provide conservation services but need to inspect the coin first to make sure the process won't make the coin worse.  Sometimes what you uncover under the problem area is worse than the original problem.

Any form of abrasive cleaning; rubbing with a cloth, polishing, etc is a big NO NO.  NEVER.  It will leave hairline scratches which will be noticeable to any decent collector. 

If you want to try your hand at dipping get yourself some 90% US Silver Coinage; it can be had at near spot (let me know if you need any) and play around with some MS 70 Coin Cleaner.  https://www.amazon.com/MS-70-oz-Coin-Cleaner-Bottle/dp/B000YQBZPE

Do not attempt to dip/clean/conserve a valuable coin as an amateur/hobbiest.  You will 100% make the coin less valuable.

Here is a great tale of an amateur who cleaned a rare coin with horrible financial ramifications:

https://www.youtube.com/watch?v=mk0F_sQY-kM

[CanaryInTheMine]

Hi, I have been looking at a few 2011 brass Casascius coins that appear to have some tarnish on them but otherwise look to be in pretty good shape. Is it possible to use a brass cleaner (like Weiman Brass polish, or Brasso metal polish) on the front of the coin at least (not anywhere near the hologram) to clean them up, or is this just a Bad Idea that will cause issues?

Are the brass coins (and silver coins for that matter) prone to tarnish in general, if not kept in an airtight storage container?

Thanks in advance for all guidance here!

absolutely no cleaning.
put in in an airtight, never handle with bare hands, get it sealed in some container, like a grading slab.
besides no cleaning rule for coins, no one has ever tested the effects of chemicals on the hologram itself.  It may react and your priv key could be lost.