Have you tried the chemical MS-70?

I have an old bottle of KOH in the garage, perhaps I should dissolve it and do some experimenting.

 

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Me and others. Don't rub it as in the case that the green is hard and crystalline it may hairline the coin.

 

IMO, this is an example of an answer that can be considered a "non [not complete or detailed] answer."

Question: "If MS70 is used on copper and turns it blue, can you easily undo it?"
ANSWER: "Yes."
Extra Detail yet still not complete but as far as I'm going: "No need to dip it into anything."

Question: "Do you have to dip it again with something else?"
Answer: "No."
Extra Detail: "See above."

This subject might be covered in Brian Siliman's ANA Conservation Seminar. Brian worked at NCS. I have not taken his course.

 

Books - The initial answer to the OP seemed a bit concise to me, assuming that the OP was sincere in looking for help. When a question such as "Have you tried it?" is asked, it seems to me an answer such as "yes" falls somewhat short on detail. True enough "Yes" is an appropriate answer to "Have you tried it", but it doesn't help much. I've been forthright declaring my comments as opinion.

Obviously, a question to clarify a question would be completely reasonable (again, IMHO).
Best,
Jack

 

Ahh.. now I see what you were trying to say, and it is certainly most reasonable. Thanks for the clarification.

 

MS70 is not a dip. It is meant to be used with some very light mechanical motion such as a Q-Tip being gently swabbed over the coin's surface.

I then rinse with warm water and pat dry with clean cotton rag.

 

I know you know your stuff, but rubbing a coin with anything kind of freaks me out unless it is a well-worn coin.

 

I understand what you saying but I don't use pressure on the surface. MS70 is more like a soap but it DOES affect tone. It doesn't so much remove it as change it. Just soaking it will not do the trick. One has to VERY LIGHTLY smooth the liquid over the surface of the coin and even continue the action until whatever you are trying to remove is gone. It even does a fair job of removing glue residue or tape residue.

If you have brilliant colors, they will be reduced to a dull monotone. It is meant mostly for BU/Proof coins but if used on AU or slider pieces, it brings out the wear and hairlines strongly. Say you have a dirty common Peace dollar that you believe is BU under all the dirt or ugly tone. MS70 will remove the dirt and some of the tone and you may be left with a bright, basically white BU coin. If there is any wear or hairlines at all, removing the dirt/tone and brightening the piece will show you any high point rubs or slider hairlines.

 

The presence of NaOH or KOH in MS-70 means that it will have a saponifying (soap making) effect on many organic residues. The most common plasticizer for PVC is dioctylphthalate, and NaOH or KOH would destroy this. A strong stream of water is often sufficient to move stubborn residues off of coins. The only time I would really worry about "rub" marks on a coin would be if it were a nice BU piece or a Proof.

 

I'll just say: copper that has been turned blue by MS-70 looks suspicious. The blues/purples/magentas that come out with MS-70 appear unnatural, although some find them attractive.

The TPGs will often give it a "questionable toning" or "altered color" bodybag to MS-70'd coins. I wouldn't recommend using it on copper coins.

 

Actually, I consider any liquid that I "dip" a coin into to be a "dip." So IMO, MS-70 is a "dip." It is used to remove things from coins just as "E-Z-Est" coin dip.

IMO it is best NOT TO RUB a coin with anything.

 

To each his own. I and the dealers I have taught use it on almost every metal. See post above for tin, etc. I probably use 1-2 bottles a month and we order it a dozen bottles at a time. The action of the product and its color has changed over the last two decades (we keep some "good" stuff for special cases); however the manufacturer claims that they have not changed the original formula.

 

What I vaguely understand of chemistry leads me to believe that one should almost never leave copper in an acetone bath for eight hours... From what I recall (and Thad will most certainly have a better explanation), copper + acetone + water vapor (moisture in the air?) will result in copper-acetate and acetic acid over time. This is one of the reasons that I generally use acetone as my final stage bath for acetone soaked coins, as opposed to distilled water. The acetone will dissolve whatever remnant organic material (and "wash away" the contaminated acetone) then evaporate in the air. Yes, this results in white coins sometimes, but, as others have said in the past, that white stuff is damaged coin.