Polishing, Cleaning, and Chemical Enhancement Methods Used On Coins
First, consider that coins coming in for certification may be rejected because they have been polished, cleaned or chemically enhanced (as opposed to natural toning). That means a great deal of people are buying coins from sources that have cleaned the coins or else the people submitting coins to the service have cleaned the coins.
a) Cleaning Coins -
Experienced numismatists will usually say that a coin is best left alone and not cleaned, However, most beginning collectors have the idea that "brilliant is best" and somehow feel that cleaning a coin will "improve" it. As the penchant for cleaning seems to be universal, and also because there are some instances in which cleaning can actually be beneficial, some important aspects are presented here.
All types of cleaning "good" and "bad" result in the coin's surface being changed, even if only slightly. Even the most careful "dipping" of a coin will, if repeated time and time again, result in the coin acquiring a dullish and microscopically etched surface. It is probably true to state that no matter what one's intentions are, for every single coin actually improved in some way by cleaning, a dozen or more have been decreased in value, Generally, experienced numismatists agree that a coin should not be cleaned unless there are spots of oxidation, pitting which might worsen in time, or unsightly streaking or discoloration.
b) Processing, Polishing, and Other Mistreatment of Coins -
There have been many attempts to give a coin the appearance of being in a higher grade than it actually is. Numismatists refer to such treatments as "processing". Being different from cleaning (which can be "good" or "bad"), processing is never beneficial.
Types of processing include polishing and abrasion which removes metal from a coin's surface, etching and acid treatment, and "whizzing", the latter usually referring to abrading the surface of the coin with a stiff wire brush, often in a circular motion, to produce a series of minute tiny parallel scratches which to the unaided eye or under low magnification often appear to be like mint lustre. Under high magnification (in this instance a very strong magnifying glass should be used) the surface of a whizzed coin will show countless tiny scratches. Also, the artificial "mint lustre" will usually be in a uniform pattern throughout the coin's surfaces, whereas on an Uncirculated coin with true mint lustre the sheen of the lustre will be different on the higher parts than on the field. Some whizzed coins can be extremely deceptive. Comparing a whizzed coin with an untreated coin is the best way to gain experience in this regard.
Often one or more methods of treating a coin are combined Sometimes a coin will be cleaned or polished and then by means of heat, fumes, or other treatment, an artificial toting will be applied. There are many variations.
When a coin has been polished, whizzed, artificially re-toned, or in any other way changed from its original natural appearance and surface, it must be so stated in a description.. For example, a coin which was Extremely Fine but whizzed to give it the artificial appearance of Uncirculated should be described as "Extremely Fine, whizzed". An AU coin, which has been re-coloured should be described as "AU, re-colored". The simple "dipping" (without abrasion) of an already Uncirculated or Proof coin to brighten the surface does not have to be mentioned unless such dipping alters the appearance from when the coIn was first struck (for example, in the instance of a copper or bronze coin in which dipping always produces an unnatural color completely unlike the coin when it was first struck.
Now that we've talked about the detriments of 'processing' coins, it is important to realize to apply these factors to coin grading and encapsulation at the grading service.
Many inexperienced coin graders equate brilliance with grade.
This human nature aspect of the hobby is responsible for a big percentage of
the problem. Therefore, individuals who submit coins may he advised to
reconsider which coins they submit. We suggest the same methods used at the
grading service. First, prescreen your submittals. Look for abrasion, excess
scratches, brown residue from chemicals (it hides in crevices , inside letters
and especially inside the reeds on the rims) and, of course, environmental
problems like green corrosion, pitting and foreign residue, Suspect coins
should be culled out. This will eliminate the number of "no-holder" coins,
cost less and also get your slabs back much quicker. At the grading service on
occasion, many individuals submit coins they have been told are one grade just
to find out it's not. True, grading coins can never be completely scientific
in all areas but there are several factors that can be pinned down which will
completely define the actual grade of a coin. Considerations, such as
striking, surface conditions of the planchet, the presence of heavy toning
(which may obscure certain surface characteristics), the design, and other
factors each lend an influence. That's why coins that have been processed are
so important. At t he grading service, we have a criteria for encapsulation
based upon a host of rules. For example, the service is more lenient in the
very low grades (AG3 to VG8) since the basic criteria of grade is much more
defined. However, from A 50 to MS70, the standards tighten up. It is these
grades where value is so c rit i cal and therefore the problem area for
"processed" coins. Our conclusions about why people clean coins, be it a coin
company or an individual comes from 2 basic facts:
1) Sellers seeking an unfair mark-up may over grade or
"process" coins for purposes of profit.
2) Inexperienced coin collectors ore often misled into thinking that coins should be treated like pieces of "fine silverware"... the more you rub and polish, the prettier they'll be Furthermore, the temptation of cleaning a coin whether it be in a cip or with chemical agent seems to be more of a temptation than the consequence.
The solution of overgrading or cleaning is to think for yourself. This brief summary only characterizes the problem and possible solutions, All grading services grade "virgin" uncleaned coins with the highest marks, Let the experts do their job! You'll be a lot better off financially for doing it. Also, stay away from chemicals like jewelustre, Numisol, baking soda and other reactive agents that leave residue on the coins.
B. The Meaning Of Mint Luster
Most coin collectors are- familiar with the term "mint luster" (or luster). However, many are at a los s to describe it, and it is likely that most do not know the cause of it. The American Numismatic Association's "Official ANA Grading Standard for the United States Coins" and James F. Ruddy's "New Photograde", the two most commonly used grading guides for U.S. coins, only devote two sentences each to define the term. The presence or absence of mint luster is an important characteristic of a coin's surface, and it is to the collector's advantage to be able to recognize it and to understand it's origin.
Mint luster is formed during the minting process. The surface of the die that strikes a planchet has slight irregularities When the die strikes a blank planchet, metal flows into the recesses of the die and outward toward the rim. The irregularities in the die are reproduced on the surface of the coin, Moreover, the flowing metal the surface of the die with faint lines called flow lines. These flow lines lines become more pronounced as the die is used . The flow lines cause the formation of ,dials on the surface of the coin which fan out from the center and are most visible near the edge but are also visible near the raised design, letters, and date. The irregularities transferred from the die as well as the radials are readily observed under a microscope. The radials appear as tiny ridges and valleys When light strikes the surface of the coin, it is reflected in all directions by the Irregularities and radials, giving a soft diffuse appearance to tone coin's surface. This appearance is sometimes referred to as mint frost.
A coin having mint luster will show the cartwheel effect. The cartwheel effect is similar to the effect shown by a rapidly rotating stagecoach wheel. The wheel will appear to be rotating slowly in a direction that is opposite to the actual direction of rotation. When a coin having full mint luster is tilted back and forth in the presence of a light source, the direction of the diffused light reflected off of the surface will change from clockwise to counterclockwise as the direction of the tilt is changed. The writer has found that the cartwheel effect is easier to observe if the light source is off to the side rather than directly over the surface of the coin and if only one light source or direction is present. Having more than one light source coming from different directions will produce than one direction of reflection of light, causing the cartwheel effect to obscured. It can sometimes be difficult to observe mint luster on a coin at a coin show. The brightness of the dealer's lamp will make the cartwheel effect difficult to observe, especially if it is directly over the coin. Sometimes it is helpful to move the lamp off to the side or to hold the coin a little below the top of the dealer's table.
Not all coins will exhibit the same degree of luster. The amount of luster present on a coin will vary depending on the extent of the irregularities and flow lines that were present wheel the dies used to strike it. As discussed above this extent changes over the lifetime of a die. Coins struck from new dies do not show as much luster as coins struck from older dies. Proof coins do not show mint luster, These coins have highly reflective mirror-like surfaces. This is because the dies used to strike them are highly polished and do not have the usual irregularities and flow lines. Coins struck for circulation from new dies (sometimes called "first strikes" or some similar term) often have proof-like surfaces. This phenomenon is commonly observed on uncirculated low mintage coins. An example is quarters minted in the 1880's, where the total mintage per year was under 16,000 pieces. Sometimes it is difficult to distinguish whether a particular coin from this era is a proof or a business struck piece. The writer recently examined at a major auction a toned 1880's quarter which was cataloged as a proof but exhibited a weak but definite cartwheel effect, indicating that the coin was actually a business struck piece. Morgan dollars and other type type coins having prooflike surfaces often command a premium in price in the marketplace Cameo proof-like coins (frosted and prooflike fields) often command even higher premiums. A weakly struck coin does not show regular luster on the raised flat areas because these parts of the coin's surface did not touch the dies during striking. A different texture dull luster will be present in these areas, which can be seen under a microscope. Mint luster is easier to observe on large size coins than on small coins. This is because these coins have more and larger radials (flow lines). Therefore, when learning to recognize Lhes presence of mint luster on coins, these are good coins to practice on. Toning will tend to hide mint luster. Luster on a deeply toned coin may not be visible to naked eye, but it can be observed under a stereo microscope. The composition of a coin as it relates to mint luster is not an important factor. However, it appears to the writer that luster on buffalo nickels is not as readily observed in terms of the cartwheel effect as luster on nickel coins of other design types.
An uncirculated coin will exhibit full mint luster. As a new coin is circulated the peaks of the radials on the high points of the design will bend and then gradually wear. This impairment of the luster will cause the cartwheel effect to no longer be perfect. As the coin is tilted, there will be a break in the cartwheel effect in those regions of the coin that have been worn, i.e. the high points of the coin. These regions will show a slightly different color than the rest of the coin and will be duller than the lustrous regions. Coins grading almost uncirculated (AU) are sometimes dipped to remove the dullness. This causes the dull areas to become shiny. As the amount of wear increases, the extent of the break in the cartwheel effect also increases. Coins that grade extremely fine (EF or XF) will show the cartwheel effect near the edges and in the protected areas. A slight break in the cartwheel can be difficult for an inexperienced collector to observe. Many coins grading AU may appear to give a full cartwheel effect, when in actuality the cartwheel effect is present mainly in the fields and protected areas of the coin. It is important to observe whether or not the cartwheel effect is present on the devices (design elements) as well as in the fields. This can be difficult to ascertain near the center of the coin, but this can be done with experience. Examination under a stereomicroscope is very valuable for making this determination. A pocket light scope having a magnification of 30X is very useful for doing this at coin shows and in coin shops. At a bare minimum, a good magnifying glass should be used. It is recommended that any uncirculated coin be examined for full luster (as well as for other important characteristics) before it is purchased. This is particularly important if it is expensive.
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