Do coin stores and dealers clean coins before selling

If you think that it is beneficial to treat (clean) coins to prevent further damage from environmental contamination, then how could you not also think that in many instances that dipping a coin is also beneficial to prevent further damage from terminal or near terminal stage toning ? Toning, if allowed to progress unchecked, will destroy luster on a coin just as surely as any coin dip or harsh cleaning will destroy that luster.

Now that is not to say that any and all toned coins should be dipped. They most definitely should not be ! But there are a great many coins which have very ugly and unsightly toning which few collectors would ever want, that if dipped and returned to their state of beauty would readily and easily find a home. And many more that have that terminal or near terminal toning that if not dipped will be destroyed forever.

Point being, dipping is just as much a conservation effort as any other conservation effort, and maybe even more so. But just like any other conservation effort you need to know when to do it and when not to, and you need how to do it.

When you consider that 80% or more of all older coins have been dipped, then you are forced to realized that dipping a coin has saved the vast majority of all of the coins that we love, not only for us but for future generations as well. It could be said that dipping coins correctly is arguably the best thing that has ever come along.

 

Oxides reduce the chemical potential of the surface of the coin, thereby suppressing the rate of further oxidation. Toning generally is very uniform, and quite different from an accelerated localized reaction due to contamination or a concentrated catalyst.

A coin that has spent 100 years toning gradually, and now exhibits darkly toned surfaces, retains more original luster than if it had been dipped 4 or 5 times in the same period. While not necessarily attractive, the toning on the coin probably represents what it will eventually return to after the dipping.

With each successive dipping, a coin loses surface area. Less surface area under the same conditions of exposure means faster and more oxidation. It is a vicious cycle to which these coins are subjected, with the results being less satisfying each and every time they are dipped.

While you probably get satisfaction from stripping a darkly toned coin white, another coin you passed on for lack of luster likely fell victim to the very same practice you espouse.

Like many others out there, I went through a dipping phase in my twenties, and learned a lot . . . mostly that I regretted it.

 

Yes, existing toning does slow down future/additional toning, but it does not stop it. On that we agree. But toning, other than the typical gun metal grey toning, and envelope toning, is rarely uniform. On the contrary, toning almost always starts at the edges of a coin and works its way inward towards the center of the coin. Thus the outer areas of a coin are subjected to much more severe toning than the center of the coin is. And once those outer areas of the coin reach the terminal stage then the coin will have suffered irreparable harm and damage.

Yes that is true. At least it is true as long as that dark toning has not reached the terminal stage. But pretty much any coin that has been dipped 4 or 5 times will have no luster left at all.

I disagree strongly. The only way that could be true would be if the coin were stored in exactly the same environment and in exactly the same manner as it was previously stored. And while it is not impossible for that to happen, the probability that it will happen is almost nil.

Toning is dependent upon hundreds of variables, change the variables and you change everything about the toning. You not only change the way it looks, you also change the speed at which it happens.

Yes.

No, the exact opposite is true. A freshly minted coin with full luster will tone much faster and much more readily than a dipped coin will - when subjected to the same conditions. This has been proved time and time again.

Why ? Because it is the luster itself that is the most susceptible to toning. So if you reduce the amount of luster by dipping the coin, you reduce the coin's susceptibility to toning.

The reason that some people think that what you are saying is true is because they are not dealing with or making comparisons with freshly minted coins. Instead they are dealing with and making comparisons between coins that were minted some time ago and that already have a degree of toning on them, (all coins begin toning the instant they leave the dies), to freshly dipped coins. As you mentioned above, it is that existing toning that slows down the rate of any additional toning.

Not all coins are dipped and then dipped again, but I will agree with you that some are. There is no doubt at all that many coins have been ruined by over-dipping. But by the same token there were and are just as many, and probably more, coins that were ruined by allowing toning to progress unchecked until it reached the terminal stage. What I espouse is saving the coins that need saving, but only those coins.

The fact of the matter is that over-dipping and allowing unchecked toning are both equally as bad as the other. Both have destroyed more than their fair share of coins. The object, the goal, is to save coins from both forms of damage.

You can save a coin that does not already have it from terminal stage toning with proper storage. You can't save it forever but you CAN save it for a very long time. But once a coin has toning that has nearly reached its terminal stage, proper storage can no longer save it. However, dipping the coin can.

And in those cases, dipping is most definitely a good thing

 

I beg to differ on this count Doug. The reduction in reactive surface area of the coin makes available more oxidizing potential per unit area of exposed surface, thus accelerating the process.

Might be good for a chemist to chime in here . . .

 

You partially have the right reason, but you are thinking about it incorrectly.

This is what the surface of a coin with luster looks like - /\/\/\/\/\/\/\/\

this is what the surface of a coin with no luster looks like - _____________

Which has more surface area ?

It must also be understood that luster is extremely fragile. And the reason it is extremely fragile is because the tops of the peaks, (and that's all luster is, a series of peaks and valleys), are very thin and rough. It's almost like a single tiny particle of metal sitting on top of a pyramid shaped pile of similar tiny particles. And since the particles are so tiny and have rough surfaces they are very susceptible to the effects of toning.

The surface of a coin without luster however has a surface where the particles of metal are much more tightly packed together, protecting each other from the air on all sides except the very top. And this creates a semi-smooth surface. Much like the flat line I used in the illustration above. That simple illustration really explains it all and proves my point.

 

None that I have ever run across, at least none that explain it the way I explain it. I think I've probably written more about it on this forum than you will find anywhere else. I started using that illustration many years ago when trying to explain luster, toning, and the interaction between the two in a way that was simple and easy to understand. In more recent years attendees at the classes held by the ANA report that the ANA instructors are using the same illustrations now in their classes. Whether they copied the idea from me, or came up with it on their own, that I cannot say.

But my comments, simple illustrations, and explanations of the subject have caused or inspired other members of the forum to take highly magnified pictures of the luster on various coins. Those pictures plainly show the things I explain. The pictures also plainly show something else I have always tried to explain, that being that each different series of coins has its own unique type of luster.

That said, Weimar White wrote a book about toning that focuses primarily on the chemistry involved. The information contained in the book regarding the chemistry is quite good and accurate. But, White is of the opinion that all toning is damage and that all coins should be dipped to remove that toning.

As a whole, the numismatic community completely disagrees with White regarding that. Instead, they agree with what I write about, in this thread and others, that dipping should only be done when it needs to be done.

That has also been discussed at length and many times. The only thing necessary to make it understandable is that if you are going to clean a coin, you have to know what you are doing in order to do it without damaging the coin. And simply put, most people don't.

So, rather than try to explain it all, which takes a good bit of time, it has become a common mantra to say - don't clean your coins.

In reality there is no contradiction - none. If you know how it is just as acceptable for a collector to properly clean his coins as it is for NGC, PCGS, or some other private party to do it. The key is knowing how.