Dipping is one of those numismatic terms that I heard used a lot without the kind of operational definition that I like to know. I came to learn that it meant, literally, immersing a coin in some solution that would remove 'bad' tarnish. Yet it does not seem to carry the same stigma that 'cleaning' did. The more collectors and dealers that I talked to, the more I came to believe that it is a common practice. That doesn't make it acceptable, but it should be in the open. In that regard, and for what it's worth, here is some visual documentation on the subject.

I used a commercial product that is easily and cheaply available. It contains thiourea (a known carcinogen) and sulfuric acid. I do not suggest that anybody dip their coins.

First demonstration was with a silver roosie dime - from change and with some black tarnish. These are the before and after pics for a 5-second dip.
[center]

Larger Pic


Larger Pic

[/center]
The dip almost completely removed the tarnish with none of the abrasive hairlines from other cleaning methods. I would grade this coin as a VF25 and might be a bit suspicious of why it had all that wear with none of the 'dirt', but the dipping is otherwise undetectable (to me) even when using a 5x loupe.

But what about an AU/MS coin? That is where dipping is used the most. So, here is a 40% silver Kennedy that I got from a roll search.
[center]

Larger Pic


Larger Pic
[/center]

I'm not sure what you see, but to me, the dipping removed most of the tarnish without removing any of the luster! I see why it is a popular practice.

The two coins were pretty expendable and I wanted to try one more experiment with a coin that would be a more likely candidate for dipping.

This is a 1964 2 1/2 Gulden from the Netherland Antilles, KM# 7 , .7200 silver, 25 gms (.5787 oz of silver) - for which I paid $12. As you can see, it was not stored in the best of condition and judging by the $3.50 original price, I would speculate that it was in the 2X2 for at least 10-20 years.
[center]


[/center]

The obverse has a considerable amount of black tarnish that is not particularly attractive. The reverse is only slightly tarnished. Looks MS to me with plenty of luster still visible.
[center]

[/center]

After dipping for a few seconds, the tarnish is largely gone and the luster remains. Ask yourself honestly which coin you would rather buy?
[center]

[/center]

I don't like dipping. I especially do not like knowing that I cannot easily tell if a coin has been dipped. Perhaps I should simply assume that after a certain amount of time, a silver coin will either show toning (attractive or not) or it has been dipped. Further, if only a single 'professional' treatment is not damaging, what about the next time and the time after that? After all, dipping is stripping the surface - period. That can't be good and I don't believe that it can be applied with such technical precision as to not cause some stripping to the 'true' surface of the coin. Pessimistically, I fear that many more coins than we generally acknowledge have been dipped. 'Blast white' may often be a synonym for 'dipped'.

So that is that.

You should get that Coin Chemistry book

Toning=Corrosoion which just means that some of the coins surface has reacted to for a corrosive compound. Dipping does not undo this process, it basically removes part of the coins surface. Mostly the toned/corroded area but also a bit of the rest of the coin. Thus the longer the total exposure to the dipping solution the more impact on the natural luster. Many raw Morgans have been dipped to the point of having no natural luster.

Coins that are left in the open air, in paper envelopes, wood cabinets, cardboard, or many other storage cointainers will tone. But, if coins are protected from the environment, and sulfur compouds they can remain blast white naturally.

I agree, but just how did they do that 100 - 150 yrs ago before modern coin holders existed ?

I believe that syzygy is 100% correct when he says -

A nice experiment. Thank you for sharing this information with us. From your pictures it's not obvious to me that the coins have been dipped. The Netherlands coin is significantly improved and would certainly be a more attractive buy after the treatment.

I've seen pictures of coins from NCS in their before and after state and some are even more radical a change than what you have shown. I'm not sure their process is the same as yours, but I'd bet it's pretty close.

Good pics and experiment. To me... The first one show why you should not dip circulated coins, the second shows that dipping is not a cure all and the third shows why some people do dip coins.

Did you use any solution to completely remove and neutralize the dip? I once bought a Kennedy that was nice and white but within a month it developed ugly brownish toned spotches all over it. I am about 99% positive it was dipped and not rinsed

All three were put under running water for about 10 minutes, but only the 2 1/2 G was rinsed further with distilled water. I certainly will report if there are some dramatic color changes later as I plan on keeping the coins.

I got intrested by all these discusions so I just ordered the second edition of the introduction to coin preservation

Of course it is in German and of course being an introduction only it is only 200 pages

German being my fourth language and the book probably being full of chemical redox raction it will take me like 3 month to understand

http://www.lindner-falzlos.de/eshop2/index...roducts_id=4306

In Coin Chemistry the author did a test in his kitchen. He put some silver spoons on the wall and two in tin containers that were common in the 1800's. Sure enough the protected coins did stay brilliant. While most storage methods from the 1800's would probably lead to toning, it was possible to prevent it.

That doesn't prove that most coins haven't been dipped, it just shows that a white coin MAY not have been dipped.

Well that's cheap, I should get one. It is my first language

Great experiment!!!

I have dipped a couple of coins to remove really ugly tarnish. So ugly that nobody would call it "toning", and it works pretty well for a ONE TIME application. I found, on a cheap MS Canadian silver dollar, that the second dip in JeweLustre will begin to affect the lustre. Over-dipped coins appear "washed out" in hand - as if the natural mint lustre just isn't there.

The penchant for some dealers to dip AU and MS coins, usually resulting in asking prices higher than actually warranted, compels me to search out naturally toned coins, especially larger sized silver.

I ordered it from Lindner themselves since there is a dozen copies of edition one for sale on ebay announced as new
Which they are but outdated and they only want like 3 euro for the edition one copies
So I decided I would rather pay the extra 7 euro for a second edition and not to take any chances I ordered it from Lindner

Well done syzygy, I have a couple Mint state CC morgans that have started to get blotchy , milky spots on them , just like Stu's example, which leads me to believe they were dipped and improperly rinsed. I almost want to sell em and "upgrade" my set by getting the same date in XF-AU.

syzygy, Wow!

Great information! Great Pics!

Big thanks!

-Bobby

One of the most informative threads ever.Well done!

Interesting thread. Looks like I'll have to start reading about this more. Have some nasty coins I'd like cleaned up a bit.

This is not the Kennedy I was talking about but here is a Washer I have that I suspect had something done to it. It sure turned bad after I had it for a while ...

I just got some cleaner and some Dells darkener. So I'll try an experiment or two in the next few days.

Yeah, that splotchy toning can be a sign of a dipped-and-not-rinsed-and-dried-properly coin

I agree it's possible. But is it probable - that's the real question. Kinda curious though, did the author mention how long he kept those spoons in the tin containers ? The answer doesn't really matter, I'm just curious.

What matters to me is this - say an owner kept his coins in a tin container and it did prevent them from toning. What about the next owner or the next ? With a coin that's 150 yrs old, it is likely that at least 6 and possibly even 40 or 50 different people owned that same coin during the course of 150 yrs. To think that all of them kept this coin in some type of container that prevented toning just isn't realistic or very probable. Do you see what I mean ? So an experiment such as you describe in the book is pretty much meaningless. It only shows what was possible to happen for a fraction of the coin's life.

My purpose is not to be argumentative, I only intend to stimulate thought and common sense. In my opinion too many authors, so called experts, conduct experiments and such and then form conclusions that are based on assumption instead of facts. It's always possible for anything to have happened. But if the probability of those events occurring is slim to none then what do have ? Not much I think.

Just like it's possible that an asteroid will strike the earth tomorrow and wipe out all life - I really aint too worried about it actually happening.

The silver spoon experiment was done over a year. I agree that this doesn't prove anything about any given coin. It just means you cannot assume anything. Some coins will be completely natural, most white ones have probably been dipped at least once. I wouldn't say the probability is slim to none though. Morgans sat in bank vaults into the mid 1960's. The coins buried inside bags were probably prety well protected by their neighbors. Since coin collecting was quite popular by then it's not that unreasonable to find fully original Morgans.

Bust halves are another matter

Here's a case where dipping worked quite nicely. It;s my specific gravity calibration coin, a 2002 Silver Eagle. The dip used was e Z est Coin Cleaner.

Before:



After:

Is there a thread somewhere that explains how that works?

I have a coin that according to Krause, has two varieties for the same year- same size and weight, but different silver content: 0.500 and 0.900. I do not know which mine is.

If it's a modern coin, you should be able to tell by weight? Or is it not listed like that?

Specific gravity is just weight in air / weight in water. .900 coin silver will give you a 10.3 +- .1 if you are doing it at home. .500 will be considerably less.

Here's one where the e Z est Coin cleaner did little, the Nic a lene coin cleaner seemed to work a bit better.

Before



e z Est:



nic a lene

Both are listed at 25g.

I could measure it for you. If you have a scale to .01g and a way to suspend the coin in water the you can do it yourself.

Is the coin silver or copper-nickel?

It's silver

I am absoutley sure that many of my "white" silver crowns have been dipped at some point.

@ jlueke

That nic a lene is impressive
Does it say what acid and other goodies are inside ? I never heard that one mentioned before

Unlike the thiourea and sulfuric acid in regular coin dips, this one is phoshoric acid mixed into some kind of detergent along with some ether.

Use at your own risk

The same company that makes nic a lene has a product for toning cents, but that one works horribly. Deller's darkener is the only way to go.

Not that anyone should clean or tone their coins anyway.

If I remember rightly phosporic acid is what makes cola work to take oxidation off nuts and bolts
All these mixtures need a wetting agent called a surfactant = soap or detergent to facilitate contact between liquid and metal
The ether probably is bis ether

http://www.chemicalland21.com/arokorhi/ind...YL)%20ETHER.htm

It does sound as if full face shield and full gloves and full labo outfit protection are necessary to mess with this one
I dislike violent reactions

What about coppers....? I've seen some awfully "funky red" samples out there,,,,, too much tobasco sauce? .... and how the heck can grading services identify dipped coins. From the examples show in this thread I don't see how they could. Is it easier to ID coppers that have been dipped than Silver?

I think copper can take on a pinkish hue after dipping but I am not positive. I have seen the pinkish colored coins though and know somerthing was done to them!

I think that is the thing with copper. It is often easier to tell when something has been done to it. At least compared to silver.

Dipped copper looks "pumpkin" colored or, as Stu said, "pinkish".
Some people out there are virtual experts in dipping and recoloring old copper.
I have a couple of what I thought were "original" large cents, but, at some point,
they had been dipped and recolored, probably using Deller's Darkener. You can't
really spot a lot of these if they have been done by one of the pro's.

If I am ever able to calibrate my pics to show copper properly I'll post some examples. Copper done with the harsh dips will turn pinkish and be easy to spot. It is possible to lighten copper fairly effectively, but since the metal is more reactive than silver it's much easier to damage the coin's surface which removes the luster and gives away the cleaning. The darkener is interesting too.

If the coins are the same weight but have a silver content that much different then the one with smaller silver content should be larger in diameter or thickness than the other.

But there is a way that should be easier, use the tissue test. Cover your coin and another coin that you know is .900 silver, side by side, with a tissue. If the coins appear to be the same color when viewed through the tissue then your coin is .900 silver. If your coin appears to be darker, then it is .500 silver.

Unfortunately I only have to one example and cannot thus make a comparison. (Nor have I been successful finding any pertinant info on the net.)




Sounds peculiar, but I will give it a try tomorrow! I am assuming that the added metal (copper?) of a 0.500 coin makes it darker in color?

I hate the haze that you sometimes see on proofs.

What would be the best way to remove this mildew look?

...Tony....

i dont know about cleaning proofs but I'm interested in the specific gravity method of measuring a coin's mass also. How exactly do you get an accurate measurement in water?

also, just for clarification...the ASE is .999 silver which would make it more dense than the 0.900 silver dollars and the silver clad .400

I've come to the conclusion that coins should be ampouled under Ar. It would help preserve them for a few thousand more years for future generations to appreciate.

Hey the slabbing companies could actually do that as part of their service. Especially for coins like proofs where the blast whiteness is the important feature.

This is a proof and has the yuk on it.

I think that most MS silver coins have bee dipped at some point or another...in the 60's and 70's it was alright to dip your coins...it did not hurt the value...

I would bet that %90+ of the silver coins in holders have been dipped at some point

Since we are on the dipping/cleaning issue, has the coin below been messed with? If so, how do you know? Curious to see your answers.

Can't tell from that pic. The giveaway is damaged or flat luster. When you see a dipped coin next to an undamaged one a few times the difference soon becomes easy to discern.

I don't see any signs of cleaning. Heck is that a DDO. The 2 looks to be very doubled.

You really have to see the coin in hand to determine if it's been dipped. It appears to have some luster but that may just be the pic. Just from the photo, there appears to be a gouge/pit at 2o'clock on the OBV. If it were originally caused by PVC damage, then it's almost a sure thing that it was dipped. There's little detail elsewhere in the pic to give away anything. I have seen coins with the dark tarnish spotting that you see above the 'W' in we. If it were dipped , you have to hold it at an angle to see the residue of the spot.


just some tricks of the trade.

Sadly.....it is not a DDO. Probably glare from the light caused that.

That Franklin had an overnight stay at the Acetone Inn to remove some dirt and grime on it. A Q-Tip finished the job. In hand there are some streak marks (not from Q-Tip) but probably from an earlier cleaning.

I have always said....don't do ANYTHING to your coins unless there is PVC present that can be removed...the ONLY thing I will ever put on a coin is blue ribbion to remove active PVC.... I can tell when a coin has been run through the dip...the original luster fades and becomes a little cloudy...

Eh, I bought it for $3 out of a junk bin. It was worth it in the learning experience. Gives you a first hand experience on what to look for when suspecting a cleaning.