Hopefully, this is the first of many informative and educational posts on this forum.
What I am going to attempt to do in this post is to identify certain characteristics of natural toning as well as characteristics of artificially/accelerated toning on silver coins. I can add the most value to the discussion by discussing toning on silver coins as that is what I primarily collect and possess the most knowledge about. Admittedly, I do not have a great deal of expertise regarding toning characteristics of copper, gold, and nickel. Maybe someone else can be kind enough to start another post regarding those areas. Additionally, I am not going to get into the chemical equation of the toning process and how doctors do it, what type of chemicals they use, etc.... Someone out there with a PHD in chemistry can probably do a much better job than myself. What I hope to accomplish is to help collectors begin to gain the knowledge and confidence in ascertaining whether or not a coin possesses natural toning or accelerated toning characteristics.
So that said, lets get started. Generally speaking, coins tone naturally via AIR TRANSFER. That means that the agent contained in the toning source (usually sulfur in canvas bag, envelope, cardboard coin album, mint set, etc) transfers and chemically reacts with a coin over a period of time through the air. Note: We are not talking about a great deal of distance. Usually, only a few millimeters between the toning source and the coin is all that is required. As you can imagine, a slow drawn out process of air transfer will have some unique toning characteristics that can not easily be repeated in a hasty manner.
Generally speaking, most artificial toning methods are done using LIQUID or GAS TRANSFER usually employing some application of heat to accelerate the process. That is the toning agent (sulfur from junior's chemistry set or some other chemical) is transferred to the coin via Liquid or Gas and the chemical reaction is accelerated usually by heat. There are whole host of ways this can be done including, but certainly not limited to, blow torch, bunsen burner, cookie sheets with oil, and just about any witches brew you can think of. Myself and others can probably go on forever about the methods the doctors use, but the important part I want to convey is that toning done in haste has its own revealing set of characteristics.
OK - so lets chat about characteristics. Lets look at 1) depth of toning 2) natural environments yielding consistent colors 3) running vs laying colors and 4) splotchiness
Naturally toned pieces will have depth to their toning. After decades of toning in a natural environement, the toning will look as though it is part of the coin. Artificially or Accelerated toned coins will usually have no substance to it and the toning will appear as though it is floating on the coin versus being engrained onto the coin's surface. How do you tell ? The best way is to hold the coin vertically under a halogen lamp (as close to the bulb as possible) - if the color disappears and the surfaces have a cloudy film to them, its a good chance its AT. Real color will hold under the halogen light.
Natural toning environments for the most part will yield consistent colors. A morgan dollar stored in a canvas mint bag will typically yield beautiful blending colors of cyan, yellow, and reds. A mint set or album toned Franklin Half will yield beautiful burnt orange, forest greens, and gold. A seated proof that spent most of its life in a coin cabinet will yield blue, magenta and gold. So if you know your natural colors and your natural environments you can pretty much figure out when you are holding the real thing. And conversely, if someone is trying to sell you a purple and pink canvas mint bag toned morgan dollar, you may want to think twice. No doubt there are exceptions to this rule, I just want to get across the general premise.
Running vs Laying Colors;
I think this is the best way to know whether or not you are looking at a NT or AT coin. I also think this is pretty easy to tell from a picture, as we see a little later. Lets go back to Air Transfer toning and imagine a coin residing in an album, a mint pack, a canvas bag, an envelope, a velvet tray, etc... The raised design elements of the coin along with the raised lettering will either be flush against or slightly closer to the toning source than the fields of the coin. This will cause the raised portion of the design and lettering to tone a different shade from the field or to not tone at all in the case of coins sitting flush against the toning source (or other coins in the case of a mint bag). Remember, all that is needed is a millimeter to make a difference in the natural toning progression. So how does this translate into telling NT vs AT ? In a naturally toned coin you will not see toning run over the raised design elements and letters. Rather, you will see toning laying within the lettering and more or less breaking at the design elements. In AT coins which had their toning agent applied via gas or liquid, the toning is going to run over the letters and design elements. If something is applied via gas or liquid it can not discriminate between the raised and recess areas of the coin - it is going to apply evenly. Not the case with Air Transfer. Having said all that, there are exceptions to what I just said, most notable are whitman albums which had high sulfur content and toned really thick over the peripheries and lettering. But if you understand that type of toning you can make the appropriate exception. If you combine running colors with off colors, there is a good chance you are looking at AT.
Natural toning tends to blend within the coin. You usually don't see splotchiness on a natutally toned coin. If you see excessive splotchiness on a coin, chances are its AT.
OK - lets apply what I just said between a naturally toned coin and the infamous Peace $ and see if we could spot any red flags doing a side by side comparison.
The first red flag was in the story regarding the origin of the coin. The coin was said to reside untouched an envelope for 80+ years. Now, being familiar with envelope toning, my experience has proven that rainbows rarely, if ever, come from envelopes. Usually envelope toning yields golden brown, dusky silver blue, or a pale rose. The toning is usually thick and can some times yield spots of iridescence, but never a vibrant rainbow like you might find from mint bag morgans. So if you knew your natural toning environments and what type of toning they typically yield, a red flag might of went up.
Secondly, the pictures may be off regarding the color so although the colors look "off" you can't make that call from the pics alone. However, you can't miss that perfect symetrical ring toning pattern on BOTH sides. That has a too good to be true feel to it.
Third, Compare the reverse of the Wash 25C with the Reverse of the Peace $. Look at the lettering. Notice how the toning of the Peace $, runs right over the lettering, take particular note of O in ONE DOLLAR and UNITED STATES OF AMERICA. Compare how the toning runs on the raised portion of those letters versus laying inside the lettering on the Wash 25C. Note the O's, A's, C's U's, on the wash 25C. The toning is inside the letters. The raised portion is not toned in the same manner - only time and air transfer can accomplish that. No Doctor, can ever replicate that look with the same precision. Additionally, note on the Wash 25C, how the toning more or less breaks at the design elements (the outline of the eagle, the perch, branch, etc...) On the Peace $, the toning does not distinquish between recess and raised areas of the design - it runs right over it.
I hope this helps and hope no is offended that I worked in the Peace $ as an educational point. All the points made in this post are merely my opinion.
Certainly, there is much more to add, discuss, clarify, and debate on this topic. I only have so much time and this post is long enough as it is. At this point I would like to end and encourage others to add, participate and ask questions. Whether you are a dealer or collector, newbie or seasoned veteran, knowledge is the key to this hobby. Lets start sharing it.
That's a nice post. I'm going to add one or two things only because this is such a large topic that a thesis dissertation could be written on it.
The first is that air is a gas and, as such, air transfer and gas transfer are actually the same thing. If you mean gas in terms of propane or butane then that is different, but many gases behave in a very similar manner. The other is that I always look for the "colors of autumn" on a coin. If you see coins that have colors you might expect from a sunny New England day in the autumn then you can have a pretty good feel that at least it isn't blatantly AT. Aside from that, experience is the key.
_________________________ Tom Posts are based on experience and are opinion only. Experiences and opinions of others may differ.
I usually go with my first reaction when looking at a toned coin. If it just doesnt seem right, I'll pass. If it feels right, I might buy. But since almost all of the coins I buy are for albums, and not for potential resale, if a few are AT, it really doesnt matter to me, as long as I like the look.