Coin Cleaning and Conservation in Numismatics

Coin cleaning is an integral part of numismatic conservation. When performed properly using accepted techniques, it can help maintain and preserve coins, retaining their inherent historical and monetary value. However, improper cleaning can permanently damage coins and negatively impact their significance. This comprehensive guide delves into best practices for keeping coins clean and protected.

Understanding Coin Grading, Rarity, and Value

The key to safe coin cleaning lies in first understanding a given coin’s grading, rarity, and value. This provides insight into the appropriate handling and care it requires. Before cleaning any coin, it’s essential to have it professionally graded and encapsulated by a respected third-party grading service like NGC or PCGS. The grade assigned determines a coin’s market value and rarity. Many rare and high-grade coins have acquired desirable patinas over decades or centuries of aging that should never be cleaned off. Doing so would drastically reduce their numismatic and monetary value. For guidance on cleaning without damaging value, consult reputable coin dealers or numismatic associations like the American Numismatic Association.

Significance of Grades for Cleaning 

A coin’s grade significantly impacts the approach to cleaning. High-grade coins in mint state (MS60 through MS70) should never be cleaned, as this removes their original pristine finish. Lightly circulated coins (XF40 through AU58) also demand extremely gentle care. However, lower grade circulated coins exhibit wear that allows for judicious cleaning to remove dirt and oxidation. Understanding the standards for United States coins provides a helpful framework.

Rarity and Value Considerations

Rare coins such as key date coins must be treated with utmost care. For example, an 1893-S Morgan silver dollar or a 1909-S VDB Lincoln wheat cent are specimens where improper cleaning could destroy thousands of dollars in value. Even relatively common coins in top grades like MS65 or MS66 could see significant reduction in market value if mishandled. Research using numismatic references is imperative before attempting to clean valuable coins.

The Allure of Natural Patinas 

Many collectors prize coins exhibiting natural patinas, toning, or tarnishing acquired over decades of aging. These patinas contribute allure, uniqueness, and character to each coin. Removing original patinas damages integrity and causes a drastic loss of appeal. A naturally toned Morgan silver dollar or colorful toned Barber quarter, for example, would lose tremendous desirability if improperly cleaned. Leaving patinas undisturbed preserves the coin’s status.

Cleaning Techniques for Different Coin Types

Appropriate cleaning methods depend largely on the type of coin and metal composition. Techniques that safely clean copper coins can damage gold coins, for example. It’s essential to tailor approaches based on the coin.

Ancient Coins

Cleaning ancient coins warrants tremendous patience and care. Many exhibit delicate surfaces with intricate designs worn down from centuries of circulation. Harsh scrubbing or chemicals can quickly wear away remaining details. Instead, gently soaking in distilled water and using soft brushes is recommended to slowly dissolve stubborn dirt and buildup without abrasion. Avoid over-brushing delicate areas. The goal is lightly revealing details, not removing all patina.

Medieval Coins

Medieval coins also require gentle care akin to ancient coins. Soft cotton cloths moistened with distilled water can remove loose dirt. Avoid excessive rubbing that might scratch or flatten detailed surfaces. Use light strokes and frequently change cloths to prevent accumulation of particles. For difficult buildup, a non-abrasive soak is better than harsh scrubbing which can erode the coin’s surface. Preventing further degradation is the priority.

Early American Coins 

For early American coins like colonial coins, early large cents, half cents, silver dollars, and gold type coins, extreme caution is needed when cleaning circulated examples. Many develop desirable patinas that give them character and charm. On lower grade coins, soft cotton cloths often suffice to lightly enhance eye appeal and remove major dirt buildup without destroying surfaces. Never aggressively brush or dip rare early American coins.

U.S. Small Cents

For many circulated U.S. copper cents through the Indian Head and wheat ears designs, gentle cleaning helps remove dirt and oxidation that obscures details and eye appeal. Using a soft brush with a mild soap solution can eliminate grime built up over decades of use. Avoid over-scrubbing or exposing cleaned copper to air, which can quickly re-oxidize the surface. Mishandling causes permanent damage like scratches or unnatural hairline marks.

U.S. Silver Coins

Cleaning more durable U.S. silver coins like Morgan dollars, Peace dollars, and Washington quarters involves similar care to avoid impairing surfaces. Soaking in distilled water or wiping carefully with a soft cloth minimizes damage on circulated pieces. Never rub vigorously or use alkaline coin dips. This can impart hairline scratches or an unnatural Appearance. Leaving lightly toned silver coins untouched maintains desirability.

U.S. Gold Coins

Gold is a very soft metal, so U.S. gold coins like $20 double eagles require gentle care. Even circulated coins still have remnants of original mint luster that can be damaged through harsh cleaning. For dirt removal, a soft brush and distilled water works well. Avoid over-brushing raised design elements prone to wear. Any abrasion on gold coins permanently destroys the surface. Many coin collecting enthusiasts prefer uncleaned original gold coins exhibiting natural patina.

Modern Coins

Cleaning modern coins poses high risks of impairment so should be avoided whenever possible. Bullion coins minted for investment purposes and top-grade uncirculated coins should never be cleaned, as this removes their original finish. For circulated base metal modern coins, light wiping with a soft cotton cloth may improve eye appeal slightly. However, modern coins cleaned to an unnaturally bright shine reduces their market value significantly.

Understanding Challenges Posed by Specific Coin Metals

Coin metals react differently to cleaning methods, necessitating tailored approaches:

Gold and Gold Coins

Gold is extremely soft and malleable, allowing even minor abrasion to permanently remove the surface details of gold coins. This lowers grade and appeal dramatically. As such, gold coins should only be wiped down with soft cotton cloths dampened with distilled water when absolutely needed to remove loose dirt. Any scrubbing or brushing wears away the coin’s features. Even jewelry cloths can potentially impart tiny scratches. Handling gold coins requires tremendous care.

Silver and Silver Coins 

While slightly more durable than gold, silver is still a relatively soft metal prone to wear and permanent scratching if mishandled. Methods that work on base metal coins can easily damage silver coin surfaces. Gentle wiping with cotton cloths moistened with distilled water often suffices for light cleaning. Avoid repeated rubbing or using brushes on high-grade or rare silver coins. This risks hairline surface scratches and an unnatural appearance. Letting natural patinas remain is safest.

Copper and Bronze Coins

Copper and bronze coins are more resilient than precious metal coins, allowing the use of soft brushes with mild soap solutions to remove stubborn dirt and oxidation. However, rubbing too vigorously or using harsh chemicals risks removing the metal layers exposing the core composition. Use light brush strokes inspected under good lighting to avoid over-cleaning. Preventing further deterioration and corrosion is the goal rather than an unnaturally bright shine.

Nickel and Nickel Coins

Nickel coins can withstand gentle brushing but require care to avoid over-cleaning. A soft brush helps remove heavy dirt buildup on well-circulated coins. The challenge is stopping once the basic coin surface reemerges. Going past this point gives the coin an odd worn appearance. Likewise, be wary of cleaning mint state nickel coins, as brushing removes the original luster. Discoloration on nickel coins should only be lightly reduced to reflect normal circulation.

Preventing Re-Tarnishing and New Damage

Once coins are cleaned, proper ongoing storage helps prevent re-tarnishing and accumulation of new dirt or damage:

– Use archival-quality coin folders, albums, or display cases when storing coins.  PVC-free flips made from inert plastics such as Mylar offer superior protection for long-term storage.

– For raw coins, adding carefully sized Air-Tite brand capsules enables viewing the coin’s details while sealing out air flow and moisture that can re-oxidize or spot the coin’s surface.

– Deploy sealed containers with silica gel desiccant packs to actively absorb moisture and create an ideal microclimate. Monitor humidity levels within storage units.

– Handle coins carefully over clean surfaces and wear cotton gloves if needed to prevent oils or microscopic dirt from re-accumulating on cleaned surfaces.

– Avoid touching coins whenever possible. Instead, hold them by the edges or use plastic tweezers designed for numismatics.

– To retain mint luster and prevent spotting on proof and uncirculated coins, keep them sealed in the original packaging if possible.

Regular inspection of stored coins can identify new issues early before they become problematic. This may require periodic gentle wiping. However, limit handling to only when necessary.

Dangers and Pitfalls of Improper Coin Cleaning

Despite best intentions, using inappropriate methods or tools can permanently damage coins:

Abrasive Scrubbing and Brushing

Using stiff-bristled brushes, rags, or abrasive rubbing to scour coin surfaces inevitably causes irreversible scratching and loss of metal. Even soft brushes can damage coins if used too aggressively. Always employ gentle strokes and frequently inspect under good light to avoid removing metal layers or design details. Dramatically cleaning down to bare metal destroys appeal and value.

Over-Dipping in Chemical Solutions

While mild, neutral pH coin cleaning solutions can assist in dirt and tarnish removal, prolonged soaking or concentrated dips permanently damage the metal. This imparts an odd slick appearance and removes original patinas. Limit any dipping to brief durations using highly diluted solutions. Thorough rinsing and drying is imperative.

Jewelry Cleaners and Ammonia-based Solutions

Harsh chemicals like ammonia, bleach, and hydrogen peroxide will interact negatively with coin metals. Likewise, ultrasonic jewelry cleaners can fluidly “over-clean” coins, removing metal from the surface and edges. Avoid exposing coins to any caustic chemicals that can leach out metals or alter surfaces. Even dish soap contains additives unsuitable for numismatics.

Uninformed Attempts Based on Hearsay

Cleaning attempts made without understanding a coin’s composition, rarity, and condition often lead to disappointment. Home remedies like baking soda, vinegar, salt scrubbing, and olive oil damage many coin types. Always research trusted references like NGC’s conservation guide before trying to clean valuable coins. When uncertain, the adage applies: “Don’t clean your coins!”

Signs of Improper Coin Cleaning and Damage

Several unfortunate signs indicate a coin has endured ill-advised cleaning or conservation:

– Severely discolored or spotting surfaces implying chemical interactions

– Distinct hairline scratches that disrupt the coin’s features

– An abnormal frosty or slick “over-cleaned” appearance

– Flattened design elements on higher relief coins

– Distinct wear on once-sharp rims and design edges

– Removal of original patinas and toning patterns 

– Unnatural patchy areas with metallic differences

– Cloudy hazy fields where luster is destroyed

– Harshly rubbed or abraded surfaces 

Extensive damage lowers a coin’s eye appeal, grade, and market value significantly. Major impairment is usually permanent. This underscores why prudent collectors always err on the side of caution when handling or cleaning coins. 

Recommended Coin Storage Supplies and Materials

To safely store coins after cleaning and preserve their condition long-term, use archival-quality supplies:

– Inert soft plastic capsules free of PVC: Brands like Air-Tite make capsules protecting against scratches and environmental damage.

– Multi-ring albums with pre-cut holes to avoid scratching as coins are removed or inserted. Look for screw-down tight seals to secure pages.

– Cabinet-style drawers that pull out provide consolidated storage that prevents stacking damage. Felt-lined drawers further protect delicate surfaces.

– Soft microfiber cloths: For wiping down coins, cloths with fine short dense pile avoid any potential for scratches.

– Distilled water or neutral-pH coin cleaning solutions: Harsh chemicals should be avoided entirely on collector coins.

– Cotton gloves: For handling uncirculated, proof, or higher grade coins, lint-free cotton gloves prevent skin oils and dirt transferrance to the coin’s surface.

Utilizing Coin Grading and Verification Services

Third-party coin grading and verification services like NGC and PCGS offer professional assessment and encapsulation of coins that is very beneficial for collectors. Submitting a coin to NGC or PCGS involves receiving an impartial grade, description, and sonically-sealed tamper-proof case for the coin. This process helps establish and authenticate the coin’s quality.

For many collectors, having a coin “slabbed” and graded boosts confidence in the coin’s status and provides protection for preserving its condition. Graded coins often garner higher market values as buyers have assurance in the coin’s grade. While grading costs create an upfront expense, this is usually recouped by the increased value for graded rare and high-quality coins.

Grading Uncirculated and Proof Coins

For proof coins and mint state uncirculated coins exhibiting perfect or near-perfect surfaces, grading and encapsulation helps preserve these in pristine condition over the long-term. Attempting to clean or handle coins that could grade 70, 69, or 68 risks impairing the delicate finish. NGC and PCGS safely seal these coins to retain their flawless state.

Verifying Quality of Older Circulation Coins

Grading services also provide impartial assessment of circulated and lower grade coins that assists collectors when purchasing coins sight unseen. For cleaning older coins with questionable past histories, reviewing grading service descriptions and diagnostic images helps gauge if cleaning attempts might have impaired surfaces or important details. The services sometimes note improper past cleaning.

Protecting Rarity and Value

For rare coins like the 1913 Liberty Head nickel, 1804 dollar, or 1894-S dime where only a few specimens are known, grading services carefully validate authenticity and remotely examine coins a collector may never directly handle. This protects the coin’s integrity while providing critical data about quality. Grade, descriptions, and images allow admiring these rarities without risks of cleaning or mishandling possibly diminishing their importance.

While grading does incur initial costs, protecting investment value and having absolute confidence in your coins makes it a strategic advantage for many collectors

Examining and Evaluating Coin Surfaces

Careful examination of a coin’s surfaces using a microscope helps collectors evaluate whether cleaning is required and what method is appropriate. This ties into the overall conservation process.

Inspecting for Damage or Impairments

The microscope allows coin collectors to inspect for impairments like scratches, abrasions, and uneven wear or cleaning patterns. Surface damage on a coin alters its appearance and lowers perceived eye appeal and value. Understanding the scope of pre-existing damage guides next steps before cleaning attempts potentially make issues worse.

Looking for Buildup or Dirt

Microscopes help identify the location and severity of dirt buildup, debris, encrustation, spotting, corrosion, or other issues obscuring the coin’s natural surfaces. Determining the precise nature and layering of this buildup informs choices on which cleaning methods and tools may remove it safely based on the coin’s characteristics and composition.

Assessing Wear Patterns

The microscope also enables evaluating normal even wear from circulation versus any uneven patterns potentially attributable to post-mint damage or improper cleaning. For example, odd brushing patterns or hairline scratches become visible. This provides insight into stresses the coin has endured over decades and where additional care is required.

Judging Cleaning Impact

Following any cleaning attempts, re-examination under a microscope helps determine how well the process worked. Collectors can look for removal of buildup and any new impairments to the coin’s appearance like tiny scratches. This allows tweaking techniques on future coins to improve conservation practices.

A coin’s surfaces tell their history. Microscopic examination provides critical understanding to guide coin care and retention of each coin’s uniqueness as an important artifact.

Seeking Guidance from Knowledgeable Numismatists

Given the delicate balance between cleaning and damaging coins, always seek advice from experts before moving forward with any cleaning on valuable or rare coins. Reputable dealers, appraisers, and third-party grading services provide guidance to ensure your coins are preserved safely based on their individual characteristics and needs. Conservation techniques that work for common date large cents may damage key date Barber quarters, for example. Numismatic educational organizations also provide reference materials with trustworthy guidance on proper care for all coin types. Investing in your knowledge

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