Another "easy" color indicator for an added Mintmark
Insider2
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Note the "greenish" color around the added "O" mintmark. We believe this discoloration happens over time as the solder used to attach the "O" reacts with the environment.
Note: Entire image slightly enhanced to accentuate the "green." It is lighter on the coin.
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Serious question ... what's in the solder that would react? Copper?
See http://www.doubledimes.com for a free online reference for US twenty-cent pieces
Thank you for taking the time to post another lesson.
I'm not a chemist and I don't play one on coin forums. Green colors usually indicate "copper something." Solder is suppose to be a tin and lead alloy. I don't know what the composition of "flux" is. What I do know is very many old alterations have a greenish haze around the numeral or letter so when I was learning, I never cared/bothered to ask why from those who would have known the answer to your question.
PS all sorts of substances/methods are used to attach a mintmark. We called them all solder. Obviously, when the little mintmark comes off on an acetone soaked Q-Tip, it was not put on with solder! Boy, do I have some funny stories...
I note that the entire photo has a green tinge to it which is unusual for what appears to be a Morgan Dollar. Is this coin really green? If it isn't what would the attached mint mark look like under normal, "white balanced" circumstances?
Note: Entire image slightly enhanced to accentuate the "green." It is lighter on the coin.
Using the FLORESCENT light that everyone tells folks not to use, the alteration has a "natural" greenish tint on a silver gray surface.
Here is an unaltered batch (approx. 20X):
Which do everyone prefer, top or bottom?
Is the method mainly to recognize fake coins?
@Insider2
Good lesson. As the color has changed, are you saying this is an old alteration and the color change has taken place over a number of years?
If the area surrounding the mintmark has a different color, don't automatically assume it is an added mintmark. It was a common practice to test for added mintmarks by putting a drop of acetone on the mintmark. Since many added mintmarks were attached using glue, the acetone would cause the mintmark to come unglued and either fall off or be able to be pushed off with a toothpick. The drop of acetone affects the color and appearance of the area immediately surrounding the mintmark whether it's real or fake.
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"Paper money eventually returns to its intrinsic value---zero."----Voltaire
"Everything you say should be true, but not everything true should be said."----Voltaire
The scratches seem to go away right around the mintmark. Also questionable?
The US Mint authenticators in the Department of Technology (I've been told some BS that it does not exist anymore) possibly did not wish to answer a question and told the secretary (25 year employee) to say she never heard of the lab I visited a few times, used florescent light and a Nikon SMZ-2 to examine both dies and coins.
Yes.
The ONLY thing acetone can do is remove something on the coin's surface (for example, haze or crud) causing it to become lighter. The major color we see around a genuine mintmark is BROWN from an old dip residue stain.
so heat the entire coin first and then use the appropriate metal ration and stick. HAHA just kidding. Very interesting
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I suspect the discoloration is a byproduct of heat not the solder's composition. Adhesives that do not require heat would not leave a comparable signature. UV curing adhesives (aka: the nasty stuff your dentist uses just before handing you the $1,200 bill) should be visible under short wave UV.
As for ordinary fluorescent lighting, the spectrum is not uniform and is strongest in the yellow-green part. Common lamps are not reliably useful. Here's a diagram:
[© J.D. Hooker 2002-2018. Museum of Electric Lamp Technology.]
Color can only be reliably interpreted under controlled, consistent lighting and viewing conditions.
Top picture. Great shots! Very interesting.
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This goes over my head; however, constant lighting conditions are observed in the grading rooms I've been in.
I wondered that myself.
"A dog breaks your heart only one time and that is when they pass on". Unknown
RE: "however, constant lighting conditions are observed in the grading rooms I've been in."
Constant is not necessarily correct or even useful for making any color determination. Lighting MUST be of the correct spectral distribution otherwise the human visual system will do many odd things in an attempt to give us something "nice" to see.
The "grading" rooms I've seen are ALL inadequate (to be generous) for lighting color, cleanliness, humidity and overall objective surroundings... But no matter. They will do whatever they want to do.
And as long as it is constant. Everything will be examined (good or bad) using the same inadequate conditions you mention day-in and day-out.
Actually, "constant" fails for determining color. Our visual system is not objective, so we cannot compare or assess color unless we have controlled, consistent conditions. For example, a constant and consistent fluorescent light source will NEVER permit correct color determination. As shown by the upper right chart, this type of light is deficient in everything except green and yellow. Compare to the top center chart, which is standard daylight.
No reliable color examination can be made except under standard daylight.
I'm not sure the point @Insider2 is making here is in any way undone by the light source issue. Whether the color is green or grey, it is the inconsistency in color around the mintmark that is the issue. And if it ALWAYS looks green under fluorescent light, then it is the same color in all cases - even if that color isn't green under sunlight.
All comments reflect the opinion of the author, evn when irrefutably accurate.
I suspect the discoloration is a byproduct of heat not the solder's composition.
If this is the case, then would even 'fresh' alterations show the discoloration, and not after a number of years? Or because different methods are used, some may take years to develop, where others may be readily detectable right after the alteration?
RE: "And if it ALWAYS looks green under fluorescent light, then it is the same color in all cases - even if that color isn't green under sunlight."
This is the problem: the color we see will change with the spectrum of the light source. An altered area might be indistinguishable when viewed under fluorescent, but noticeable under controlled daylight. Color can only be accurately evaluated under daylight or 5500K to 6500K illumination.
Yep. The authenticator has to evaluate a range of alteration methods.
Oops! Well, you better tell the technologists at the Treasury Department they may wish to change the light they use to examine coins and dies. As for me, I'm an old dog who cannot change my ways (45+ years and counting) or the light I use (florescent and 100W incandescent). I don't think the old jewelers and watchmakers can either. Those "Daylight" florescent bulbs may not be suitable. I just cannot see setting my scope up next to a window in sunny daylight Florida. Yikes, I couldn't work until 8 PM anymore either.
Close up shows discoloration, full image not so much.. Acetone soak did not remove the CC's.
Yep. The authenticator has to evaluate a range of alteration methods.
Treasury uses NIST protocols when needed and these include the kinds of accurate, objective color assessment mentioned. Even in 1942 Bureau of Standards was using Munsell color measurement for objective data.
I'm obviously not being clear. It seems useless to attempt a discussion on the subject.
Sorta strange the letters surrounding the mint mark have several small scratches but the newer mint mark is void of the. Just curious what is the date and denomination of the coin?
Roger, as long as the appropriate experts know what to look for and how, I'm good with it.
Thanks but I, for one, do not understand what you are talking about. I have no knowledge in Munsell color measurements, and those charts are Greek to me.
bob
I agree, you know much more than I do!
Thankfully, while a coins color is important for authentication and grading, authenticators do not need to measure it or be concerned with accuracy. Furthermore, the ability to see colors between individual human beings is too variable.
I don't know what the Treasury Dept. Technicians do any more as I left DC in 1990.
As I wrote above, the lighting I've learned to use from them does the job. Florescent light WAS being used with a microscope in a florescent lighted room! I've stood right next to one of the technicians inside the Treasury lab while he showed me what diagnostic he used to authenticate 1955/55 Lincolns. Then I showed him one he had never noticed but that is another story. Whatever works.
I will agree with some of your post. Anyone with good eyesight who is not colorblind can see that coinage metals look differently under different lighting conditions. That's why when I'm authenticating coins at a coin show, it often takes a little longer as the lighting is different from my daily location.
Oh BTW, I only use color wheels and color charts to ID the colors of POSTAGE STAMPS.
97-O Morgan dollar. Very often an added mintmark has scratches around the letter. Altered coins are usually cleaned to disguise the "work."
Be careful using fluorescent lighting for photography. They flicker at twice the rate of the AC used to power them and this flickering can interract with your shutter speed to cause color casts when taking photos. Here is an explanation of the effect for those so inclined:
https://photo.stackexchange.com/questions/4115/do-fluorescent-lighting-and-shutter-speed-create-a-problem-with-color-cast
In short, what might work for your eyes might not work through a lens with a shutter, and this would explain your odd colored photos under fluorescent light.
Hope this helps...Mike
p.s. neat thread and topic -- thanks for sharing.
It's a NIGHTMARE with STAMPS, especially 19th century stamps where the pigments were mixed by hand and prone to a wide range of colors. Then, the inorganic pigments were subject to oxidation over time creating an even wider range of colors due to differences in storage environments. "Pigeons blood" my arse!
All comments reflect the opinion of the author, evn when irrefutably accurate.
In an effort to maximize consistency and objectivity, all graders, handlers, observers, and photographers of coins must now wear color spectrum limiting eye-wear.
Collector, occasional seller
The spectrum of light is not directly affected by alternating current. Modern fluorescent lights also have phosphors that help suppress the flickering. In any case, fluorescent is a terrible light type for examining stamps, coins, or cattle prods.
Look at the spectrum charts, above, again.
Roger, If your post was directed at me, I am well aware of the spectrum of different types of lights and the different types of fluorescent bulbs (and even ballasts that work at higher frequencies).
While you're right that the spectrum of light is not affected by AC, the way a camera with a shutter captures color can absolutely be affected. I've seen it in my photos and it's plainly seen in the examples in the link I posted.
Take care...Mike
p.s. FWIW, I'm not a big fan of fluorescent lights for coin viewing. either, but to each his own.
Mike, no it was not directed at you, or anyone specifically.
RE: "While you're right that the spectrum of light is not affected by AC, the way a camera with a shutter captures color can absolutely be affected. I've seen it in my photos and it's plainly seen in the examples in the link I posted."
Sorry, but that is not correct. A camera shutter is simply a mechanical element - it does nothing to light color or anything else. It only controls duration. The color shifts come from non-mechanical parts of the imaging system including CCD response profile, readout defects, software, even source voltage fluctuation and contamination from changes in ambient lighting.
Thank you for the follow-up, Roger. Yours is a much more accurate representation of what's going on. However, I was always under the impression that the shutter also had something to do with it as the color cast often only occurs in part of the photograph (in addition to throwing off the exposure/brightness), and the color cast seems to only show up at certain shutter speeds. Regardless of the cause, the point remains that color casts can and do happen under fluorescent lighting that are not present in other types of lighting, and on this point I suspect we both agree. Thanks again...Mike
@RogerB said: "The spectrum of light is not directly affected by alternating current. Modern fluorescent lights also have phosphors that help suppress the flickering. In any case, fluorescent is a terrible light type for examining stamps, coins, or cattle prods. Look at the spectrum charts, above, again."
LOL, and bumble bees are not supposed to be able to fly either. Have you ever used it?
PS I hope all reading our back and forth realize how knowledgeable Roger is; how much he adds to the forum to educate and enlighten us; the importance of his research projects and books, AND HOW MUCH I ENJOY NEEDLING HIM when I disagree.
I have. Several types in point of fact.
And FWIW, I think we are blessed to have both of you guys here.
If there is a color cast on part of the image, then it is likely a synchronization problem between continuous and fluorescent light sources. This can be especially noticed at higher shutter speeds of 1/125 and above. The common cause is that the continuous light source is on for the full duration of exposure, but the "flickering" light source is on only part of the exposure. Thus, part of the CCD is exposed to only one light source and part is exposed to two light sources. (The usual corrective action is to decrease shutter speed so that all of the CCD receives light from all of the sources.
Mechanical components cannot affect color unless they are specifically intended to do so by adding colored filters, reflections and so forth.
If you have a specific problem situation, let me know and I'll try to figure out a solution.
Bumble bees are not fluorescent lights. (Are there any fluorescent bumble bees?)
Both work, but just as a bumble bee is not a speedy critter, a typical fluorescent light is not suitable for accurate coin examination. To use any restricted spectrum source is simply self-deception. It does not matter how long people have been doing this - it is still poor practice and can easily result in misleading and false conclusions.
I'll ask once more...do you have really have enough actual experience examining objects using florescent light (rather than hearsay or published opinions) to be able to comment on this subject with any authority?
It's OK. A "yes" or "no" will do and I'll believe you.
Interesting and educational thread... going to have to go back to this one a few times to absorb it all.... Cheers, RickO