| by James Halperin
Over time, copper and bronze coins will naturally change color
from mint red to various shades of brown as a microscopic layer of
oxidation covers the surface. This is good for the coin. The
oxidation forms a protective barrier against harmful substances
that could literally eat into the surface. Mint red copper and
bronze coins offer a “fresh” and fragile surface that is more
vulnerable and susceptible to spotting.
Under magnification, it is not unusual to find some minuscule
flecks of discoloration on red, and red and brown coins that have
been graded MS-64 or higher by a grading service. If your goal is
to locate absolute mint red large cents with pristine, spot free
surfaces, you may be in for a very long hunt. Even in the case of
modern issues, like pre-1960 Lincoln Cents, tiny spots may be
found on high-grade examples.
There are many substances that can create spots on coins.
Moisture from breath or, heaven forbid, an innocent sneeze can
eventually do tremendous damage. I knew one old-time dealer who
enjoyed lightening up a cigar while viewing coins. I wonder how
many of today’s coin spots are the result of his exhaled tobacco
smoke?
Coins are especially prone to spotting when stored in any humid
place subjected to fluctuations in temperature. If you want to be
assured of spots on your coins, store them in a cardboard box
behind the clothes dryer. Airborne chemicals and even the salt air
in ocean-side communities can add spots. I know of one collector
who lived downwind from a paper mill. After several years in
storage his copper coins had turned coal black! Never store copper
or bronze coins around aromatic woods such as those found in a
cedar chest or pine box.
A spot results when a concentrated amount of an oxidizing
substance is allowed to remain on the surface of a coin. Most
spots take time to grow. A coin might have been contaminated long
before you acquired it. Removing spots is nearly impossible.
Trying to will generally result in more overall harm than good.
When spots are found the best strategy is to suppress further
growth. There may be other products that work as well, but I have
had success using Blue Ribbon coin conditioner and preservative.
When applied to the surface of a copper or bronze coin, this light
oil-like substance will leave a thin protective film and a glossy
appearance. This same product is good for removing PVC, as well as
other forms of slime and dirt, from all copper and bronze coins.
Hopefully the following is common knowledge, yet I feel
compelled to mention this: Copper and bronze coins should never be
dipped. Liquid tarnish remover will not remove spots and your coin
will end up an unnatural -- and to the experienced numismatist,
ugly -- orange color. Dipping a copper or bronze coin nearly
always ruins it!
In closing, let me remind you that I’m not a chemist. The
product I’ve mentioned has worked well for me, but I lack the
credentials to endorse it.
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