Understanding Professional Numismatic Conservation
Posted by Brian A. Silliman on 2/7/2003
The improper cleaning, handling and storage of coins are major problems in this hobby. Anyone who has collected coins, even if only for a short time, has seen otherwise great coins that have been damaged...
This article originally appeared in Volume 51, Number 31 of Numismatic News,
a Krause publication.
The improper cleaning, handling and storage of coins are major problems in
this hobby. Anyone who has collected coins, even if only for a short time, has
seen otherwise great coins that have been damaged or had their eye appeal negatively
affected by hairlines, impaired luster, unnatural color, severe tarnish, residues
or other contaminants.
recently, collectors and dealers did not have many options in rescuing coins
that display harmful surface conditions. Professional conservators routinely
conserve ancient coins, especially those recovered from archeological sites.
Most other coins especially coins of more recent vintage, have been largely
overlooked and not conserved professionally. A notable exception of recent memory
is the SS Central America coins that were conserved after being salvaged from
the sea and brought back to terra firma.
Other than these examples of professional conservation, the vast majority of
coins in the market place that could benefit from conservation have been left
to the amateur cleaning effort of collectors and dealers or have not been conserved
While a coin can be properly cleaned, where by contaminants, debris, corrosion,
tarnish and a variety of harmful residues are removed without altering or impairing
the coin's original surfaces, many have been damaged by improper "cleaning".
The unfortunate irony of the situation is that in the process of trying to save
a coin or improve its appearance, many coins suffer even more severe and irreversible
damage such as hairlines, impaired luster, color changes or develop corrosion
from inadequate neutralization.
To understand the basis and need for professional numismatic conservation we
need to understand how and why coins deteriorate and the conservator's role
in remedying or reducing detrimental surface problems.
Coins are prone to corrosion as a result of their composition. The metallic
composition and durability of coins is one of its major advantages, but it is
also a hazard. Coins are actually very fragile and can be damaged or even destroyed
Coins are most often produced in copper, nickel, silver or gold. All of these
metals are produced from ores that are smelted from a mineral state that is
relatively stable to a crystalline solid or metal state that is somewhat unstable.
Virtually all coinage metals are a mixture of more than one metal. A mixture
of metals is used to produce a particular coinage alloy in order to attain certain
desired characteristics such color, intrinsic value and durability.
Luckily for us, coinage metals are fairly durable, especially in comparison
to other materials that have been used for money over the centuries. Had the
Greeks or Romans used paper money instead of coinage, surviving specimens would
be so rare and fragile only a collector that is as rich as Croesus could afford
coin's survival and state of preservation are influenced by the coin's environment
and this is due to interaction with the coin's metallic composition. Take for
example the survival of ancient Roman coins found at archeological sites. Coins
found buried in earth consisting largely of limestone or alkaline soils, as
may be found in farmland or countryside, may be in relatively good condition
and have only minor spots of corrosion and encrustation. In situations like
these, some coins may develop a patina, which actually protects the coin from
severe deterioration. On the other hand, coins from granite sub soils common
to more urban environs and areas of bedrock can be found heavily encrusted,
deformed and corroded by the acids in the gravel and sands. In the most severe
cases, these coins corrode and deteriorate almost completely.
While coins produced during the last couple of centuries are less likely to
be found with extreme problems like this, they commonly have debris particles,
residues and other potentially corrosive elements on their surfaces.
Debris particles are often found stuck in the recesses of design elements.
These particles can contain corrosive causing elements which overtime can develop
into severe spots of active corrosion
Other harmful surface conditions result from the handling and storage of coin
collections. Even the most careful of handling enables contaminants on your
fingers to be transferred to your coins. Oils and salts are continuously secreted
through the skin and will be transferred to the coin along with many other potentially
harmful elements that adhered to the skin through contact with other items.
To avoid putting very noticeable and often irremovable fingerprints on the fields
of a coin, emphasis is placed on handling coins by their edge, but even this
allows residues to transfer. You can sometimes see this on early copper coins
where the obverse and reverse may display an attractive brown color while the
rim has a slightly lighter and pink coloration from contact with fingertips.
In more extreme examples, the obverse and reverse may appear to be in very good
condition while small green spots of corrosion are visible on the edge and rim.
In an effort to avoid handling coins, a wide variety of storage devices have
appeared on the market place. Over the years, hundreds if not thousands of different
products ranging from flips and envelopes to books and boxes have been sold
to help collectors store and manage their collections. The earliest versions
were not with out problems. Many holders contained sulfur, PVC and a variety
of other possible contaminants. In recent decades, manufactures have become
more informed and responsible and we have seen the development of much safer
storage products. Nevertheless, not all collectors and dealers seek out these
coin friendly products, while many hobbyists have not removed their coins from
the old and potentially hazardous holders. Coins from improper holders are seen
often in the market place. PVC contamination is one of the more commonly seen
problems resulting from bad coin holders and in many cases corroded into the
surfaces of the coin.
Even if coin friendly holders are used, the surrounding environment can still
adversely affect a coin's condition by facilitating corrosion or tarnish.
Lets be honest with ourselves about "toning". When a coin has an
attractive pattern of colors it's called "toning". When it's unattractive
it's called tarnish or spots. And when it is very dark it's often called environmental
The terrible truth about tarnish is that it is a form of oxidation and is primarily
caused hydrogen sulfide and carbonyl sulfide. Tarnish can result from direct
contact with tarnish-causing elements or through vapors.
Some common tarnish-causing elements are wool, silk, felt, dyed fabrics, paper,
cardboard, wood and wood products to name just a few. In short, traces of tarnish-causing
elements can be found all around your house, office or shop and even in the
clothes you are wearing. Keep in mind that while you may not be able to smell
sulfur (a rotten egg smell) until it reaches unhealthy levels, coins are more
than one hundred times more sensitive to it. Add fluctuations in temperature
and humidity to the mix and the speed and effect of the tarnish-causing materials
Coins displaying the effects of any of the aforementioned hazards are prevalent in the marketplace. Their appearance may vary considerably, but it
is generally unappealing and will usually get worse over time. Likewise, the
results of amateur attempts to address these problems are also easy to find
in the many improperly cleaned or "problem" coins that display hairlines,
scratches, impaired luster, uneven or unnatural color.
The difficulty dealers and collectors experience in attempting to conserve
their coins is that they lack the technical expertise, appropriate materials
and, more importantly, experience and training. Conservation is much more
than just "dipping" a coin and drying it off. A treatment like this
may impair or damage as many coins as it helps. It also leaves the coin susceptible
to advanced corrosion, as dip residues become corrosive over time.
numismatic conservation has grown out of the need to save coins from detrimental
surface problems and preserve our numismatic heritage, while also providing
hobbyists with a safe alternative to cleaning coins on their own.
While professional conservation may be relatively new to this hobby, other
cultural and historical artifacts have been routinely conserved for a very long
time. Conservation is a very specialized field and conservators usually focus
on one type of artifact or conservation method. This specialization is necessary
because they must possess tremendous knowledge of the item they are conserving.
They must be experts in evaluating the composition, production and condition
of the item in order to be able to master the complexities of treating the item
to produce successful and consistent results. This specialization along with
extensive hands on experience ensures the conservator will make sound judgments
during the evaluation and subsequent conservation.
Before any procedure is undertaken, a careful and thorough evaluation of the
coin is made. During this detailed analysis, the evaluator assesses the condition
of the item's underlying surfaces, identifies the surface problem(s) and makes
a determination as to what, if any, treatment will be most beneficial in removing
or reducing the contamination and stabilizing the coin to limit further deterioration.
The coin's manufacture, age, composition and grade are especially important
because they influence which procedure will be most effective in producing results
of the highest standards.
Since the evaluation process is every bit as important as the procedure undertaken,
the evaluator has to have seen hundreds of thousands of coins, understand their
production and the subtleties of their luster patterns, color and originality.
Unlike other conservation specialties, the certified grading system makes the
job of the evaluator very difficult. When reviewing certified coins the evaluator
must determine if the coin will maintain its current grade after conservation.
Even though, the procedure only removes foreign material from the coin, these
materials may conceal minor marks that may affect grade once the coin's true
surfaces are visible again. This is a very important consideration, especially
when only very slight differences in luster brilliance can mean the difference
between a coin grading MS68 or MS67.
Having the most experienced evaluators and foremost conservation experts working
in unison ensures results of the highest caliber, while reducing the risk of
a coin not maintaining its current grade. In many cases, when all of the elements
work well together, coins can and do increase in grade, as their original surfaces
become visible and unimpeded by residues
After the specimen has been evaluated and a procedure is prescribed, the coin
is conserved in a laboratory setting specifically designed and equipped to ensure
consistency and quality of the results. Through the systematic application of
chemicals and solvents, the conservator is able to reduce or remove the detrimental
surface conditions while protecting the original integrity of the coin's surfaces.
In some cases, several different treatments may be used to address several different
contaminants. In addition to removing foreign materials the procedure also neutralizes
the coin to ensure longer-term stability.
The most important difference between numismatic conservation and many other
conservation specialties is in regard to the restoration of the object. In other
fields it is acceptable to "strip" down the item and its outermost
original surfaces and then restore the item by rebuilding its surfaces before
applying preservative materials. For obvious reasons, this is not acceptable
in numismatic conservation where the principle goal is to remove detrimental
foreign materials and protect the originality of the specimen's surface.
Much like the early years of certified grading, numismatic conservation has
seen its fair share of controversy. However, as collectors and dealers gain
a better understanding of the principles of professional conservation and how
beneficial it is in the preservation of our numismatic heritage, the hobby will
hopefully see a reduction in the number of "problem" and improperly
cleaned coins in the market place.
At present, there is very little useful information available on numismatic
conservation, especially as it pertains to more modern coins. However, the booklet,
The Conservation of Coins; A Buyers Guide is helpful in gaining an understanding
of importance and uses of professional conservation and the problems associated
with improper cleaning. This booklet is a collaborative effort on the part of
PNG, NGC, PCGS, ICTA and ICG. It can be viewed by clicking here
This article was originally published in Numismatic News on July 30, 2002.
News is published by Krause Publications, Iola, WS.
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