How to remove residue from 90% gold? 1 1

[Prethen]

There's some sort of blacky, ink-like residue on this 1976 Australian 1000 Schilling gold (90%) coin. Under power it does not appear as toning but rather some sort of substance on the coin. What can safely remove it? I'm out of acetone, otherwise I would have tried that already. I tried using a cotton swab and some denatured alcohol without effect.

[Coinbuf]

Acetone will be the best to use as it will not remove any of the patina the coin has.   Having said that, you might find that removing the gunk might leave the surface with bright spots that may look unnatural with the rest of the surface.   MS70 might work but it will "brighten" the look of the coin as it will remove some of the patina, word of caution, I have not used MS70 on a gold coin of this type so I cannot be certain of the effect it could have.

[Mike Meenderink]

Your gold coin is exhibiting tarnish blooms from silver impurity.  Small amounts of silver are present in this coin. The silver molecules oxidize out from very small pitts in the coin where silver impurity is concentrated. This presents as smudge black areas. Another natural process of all gold coins is black carbon spots. This is normal for aging but may be accelerated by mishandling and or widley fluctuating temperatures while in storage. I would contact NCS and have them assess your coin.

[Prethen]

I tried soaking in acetone for a couple of hours, used a cotton swap, and nothing came off...not a spec (even with some slightly aggressive prodding with a toothpick). The residue sort of makes me think of it as molten lava that's adhered itself to the surface. Maybe it is tarnish blooms or carbon. To be honest, it really doesn't matter all that much as this is really just a gold bullion coin, so it was more as an experiment and to see if I could turn the coin somewhat pristine again. I guess I'm out of luck on that.

Edited September 1, 2023 by Prethen

[Henri Charriere]

Depending on a coin's numismatic worth, and having checked numerous web sites for the definitive answer, I feel, as a collector, you're treading dangerous ground.

If time is not of the essence, why not consult David Hall?  He's been dealing with gold for over 40 years. Surely, he would know the answer to this and, having seen a photo of your coin, advise accordingly.

 

[Mike Meenderink]

On 8/31/2023 at 9:21 AM, Coinbuf said:

Acetone will be the best to use as it will not remove any of the patina the coin has.   Having said that, you might find that removing the gunk might leave the surface with bright spots that may look unnatural with the rest of the surface.   MS70 might work but it will "brighten" the look of the coin as it will remove some of the patina, word of caution, I have not used MS70 on a gold coin of this type so I cannot be certain of the effect it could have.

Baahahaha... You are really a basic moron_aren't you? You say I'm the master of misinformation well then you must be the God of bulls*it.

Edited September 4, 2023 by Mike Meenderink

[Coinbuf]

On 9/3/2023 at 5:19 PM, Mike Meenderink said:

Baahahaha... You are really a basic moron_aren't you? You say I'm the master of misinformation well then you must be the God of bulls*it.

Poor mike, trying so hard to be one of the cool kids, so pathetic but you would need a brain first.   Did you play the straw man in The Wizard of Oz, I can just see you wandering around your overpass muttering "if I only had a brain"  

Edited September 4, 2023 by Coinbuf

[Henri Charriere]

Blast from the Past. 🤣

🐓 :  You sorry you lost your "guest moderator" spot on the Forum?

H.C.:  I soy-ten-lee am.  The tried and true approach is the best.  Sit back, watch, and get to know each of the members well enough to find out where, on the imaginary pecking order, they fit in. It is always helpful to know who identifies with whom.  Social media (which VKB was kind enough to point out this Forum is but an example) doesn't lend itself very well to those given to speaking in circumspect ways.  Short of inviting the combatants to the White House to hash their differences over a glass of beer, I would advise proceeding with extreme caution.  Let's not forget, personal opinions aside, RWB was recognized as "Numismatist of the Year," and like it or not, Barack Obama was a president of the United States. Publicly, here on the Forum, for example, we must not hesitate to give them their due. As one who has been banned, banished, deported, warned, assessed points -- even sent to my room without supper a week straight, I can assure all it was no fun.  The Chat Board Guidelines are Law; it behooves all to become intimately familiar with its provisions.