Verdigris and PVC: Saving Your 1870 2 Cent Piece PCGS MS65+BN CAC Pop 2 0 Higher from Environmental Damage

Introduction: The Silent Threat to Your Numismatic Treasures

Improper storage is the enemy of numismatics—and I’ve watched it destroy some of the finest copper pieces to ever come through my hands. As a conservator who has spent over two decades working with high-grade bronze and copper coinage, I’ve seen firsthand how environmental deterioration silently erodes what should have been preserved forever. Recently, a forum thread caught my eye: collectors were marveling at a stunning 1870 2 Cent Piece, PCGS MS65+BN CAC, Population 2 with 0 Higher. It’s a gorgeous coin. But it also serves as the perfect case study for understanding the environmental threats that could undo everything that makes it special.

This isn’t just any 1870 2 Cent. It’s a condition census piece—one of only two known at this grade, with nothing finer. That kind of rarity demands our attention, not only for its numismatic value but for the conservation challenges it quietly faces. When you’re dealing with a coin of this caliber, understanding environmental threats isn’t optional. It’s essential to preserving both the historical integrity and the market value.

Understanding the 1870 2 Cent Piece: Historical Context and Composition

The Metal That Makes Conservation Critical

The Two Cent Piece series (1864–1873) holds a fascinating niche in American numismatic history. Struck in 95% copper with 5% tin and zinc, these coins present conservation challenges that silver and gold simply don’t. The 1870 date isn’t the key date of the series, but finding one in true Mint State with meaningful remaining color? That’s a different story entirely.

Let’s break down what that PCGS MS65+BN designation actually tells us:

• MS65+ signals exceptional Mint State quality—the “+” means the coin sits at the top end of its grade in terms of eye appeal
• BN (Brown) confirms the piece has developed significant toning, having shifted away from its original red copper appearance
• CAC approval validates the coin as a solid or premium example within the assigned grade—no marginal pass here
• Population 2, 0 Higher places this as one of just two finest known examples. That’s condition census territory, plain and simple

Here’s the double-edged sword: the bronze composition that makes these coins historically interesting is the exact same property that makes them environmentally vulnerable. Copper alloys react aggressively with atmospheric chemicals, moisture, and improper storage materials. Left unchecked, these reactions destroy original mint luster and compromise the surfaces that give a coin its collectibility.

Bronze Disease: The Numismatist’s Nightmare

Identifying the Green Menace

Of all environmental threats facing bronze coinage, bronze disease is the most destructive—and the most insidious. I’ve examined high-grade copper pieces where this condition lurked undetected for years, slowly eating away at the surface until the damage became irreversible. By the time a collector notices something wrong, it’s often too late.

Bronze disease announces itself through these telltale signs:

• Bright green, powdery spots that sit raised above the surrounding surface
• A fuzzy or crusty texture that looks completely different from natural toning or stable verdigris
• Progressive spread—the affected areas grow steadily if left untreated
• Pitting beneath the corrosion that permanently scars the coin’s original surfaces

The chemistry behind bronze disease is relentless. Chloride ions react with copper in the presence of moisture and oxygen, producing copper chloride compounds. These compounds hydrolyze and release hydrochloric acid, which attacks more copper in a vicious, self-perpetuating cycle. For a coin like this 1870 2 Cent Piece in MS65+ condition, even a small outbreak of bronze disease can devastate both its numismatic value and its historical integrity.

Why High-Grade Bronze Coins Are Particularly Vulnerable

You might assume well-preserved Mint State coins would resist bronze disease better than circulated pieces. In my experience, the opposite often proves true. High-grade coins with original surfaces carry specific vulnerabilities:

• More reactive surface area—without thick protective toning layers, the underlying metal is exposed
• Greater financial incentive for owners to attempt aggressive cleaning when problems appear, which only compounds the damage
• Higher scrutiny from graders—even minor corrosion becomes a significant grade-affecting issue at this level
• Longer cumulative exposure time—these coins may have sat in improper storage for decades before entering careful collections

The 1870 2 Cent Piece in question carries a BN designation, meaning it has already developed significant toning. While that toning offers some environmental shielding, it can also mask early-stage bronze disease developing beneath the surface layers. That hidden threat is what keeps conservators like me up at night.

PVC Plasticizer Damage: The Hidden Threat in Storage

How Modern Materials Destroy Ancient Metals

Polyvinyl chloride—PVC—remains one of the most common and most preventable sources of environmental damage I encounter in numismatic collections. I’ve seen otherwise pristine coins ruined by prolonged contact with PVC-containing holders, flips, and storage materials. The tragedy is that it’s entirely avoidable.

PVC damage unfolds through a specific chemical process:

1. Plasticizer migration—PVC products rely on phthalate plasticizers to stay flexible
2. Off-gassing—these plasticizers slowly release from the PVC over time
3. Chemical reaction—the migrating compounds react with copper surfaces on contact
4. Green film formation—a characteristic green, sticky residue develops on the coin
5. Surface etching—prolonged exposure permanently damages the coin’s original surfaces

For this 1870 2 Cent Piece, PVC damage would be particularly devastating. The BN surfaces, while showing natural toning, remain chemically reactive at a molecular level. PVC plasticizers bond with copper in ways that become increasingly difficult to reverse the longer they sit. Prevention is the only real solution.

Identifying PVC Damage on Your Coins

Catching PVC damage early requires careful, informed examination. Here’s what I look for:

• Green, sticky residue that appears unevenly across the coin’s surface
• Haze or film that seems to emanate from within the coin rather than sitting on top
• A distinctive chemical odor when opening older holders or storage containers
• Progressive deterioration—damage that worsens even in seemingly stable conditions
• Pattern matching—corrosion patterns that line up precisely with contact points on the holder

The forum discussion praising this coin’s “clean surfaces” and “eye appeal” suggests it has avoided significant PVC damage so far. But consider: this coin is over 150 years old. It has passed through numerous collections, dealers, and storage environments. Some of those environments almost certainly contained PVC materials. Vigilance is non-negotiable.

Oxidation and Toning: Natural Processes Gone Wrong

The Difference Between Beautiful Toning and Destructive Oxidation

All bronze coins develop toning over time. That’s natural—and often desirable. The BN designation on this 1870 2 Cent Piece indicates significant color change from its original red copper appearance. Learning to distinguish between attractive, stable toning and destructive oxidation is one of the most important skills a collector can develop.

Desirable toning characteristics include:

• Even, gradual color progression shifting smoothly from red to brown
• A smooth, satiny appearance without any raised deposits
• Stable chemical composition that doesn’t continue changing rapidly over time
• Enhanced eye appeal that complements rather than obscures the coin’s design elements
• Protective qualities that shield the underlying metal from further chemical reaction

Destructive oxidation warning signs include:

• Uneven, spotty color distribution with abrupt, jarring transitions
• Raised, crusty deposits that feel rough when examined through the holder
• Continued color change even when the coin sits in stable storage conditions
• Dulling or hazing that obscures the design details and kills the luster
• Active corrosion that appears to be spreading or deepening over time

Environmental Factors Accelerating Oxidation

Several environmental conditions dramatically accelerate destructive oxidation in bronze coinage:

• High humidity—moisture drives electrochemical corrosion reactions
• Temperature fluctuations—thermal cycling promotes condensation and increased chemical activity
• Air pollution—sulfur compounds, chlorine, and other atmospheric contaminants attack copper surfaces aggressively
• Direct sunlight—UV radiation accelerates chemical degradation
• Contact with acidic materials—paper, cardboard, and certain plastics release compounds that react with copper

For a condition census coin like this 1870 2 Cent Piece, maintaining optimal environmental conditions isn’t just good practice—it’s an essential act of preservation.

Proper Chemical Conservation: The Acetone Dip Debate

When Chemical Intervention Becomes Necessary

As a conservator, I approach chemical treatments with extreme caution. The numismatic community remains divided on interventionist conservation, and for legitimate reasons—improper treatment can destroy value faster than the damage it attempts to address. That said, certain situations warrant careful, informed chemical intervention.

Acetone treatment may be appropriate when:

• PVC residue is present and can only be mechanically removed through chemical means
• Surface contaminants threaten to cause ongoing chemical damage
• Organic deposits—oils, adhesives—have bonded to the coin’s surface
• Documented, reversible treatment can be performed without altering original surfaces

Acetone treatment should be avoided when:

• Bronze disease is active—acetone won’t stop the underlying chemical process
• Original mint luster remains—any treatment risks altering this irreplaceable characteristic
• Stable, attractive toning exists—treatment might strip desirable color
• The coin is professionally graded—any treatment risks revealing intervention to future graders

The Proper Acetone Dip Procedure

For collectors who determine that acetone treatment is necessary, proper technique is everything. Here’s the protocol I follow based on conservation best practices:

1. Use 100% pure acetone—hardware store acetone often contains additives that leave harmful residues
2. Work in well-ventilated areas—acetone fumes are hazardous and flammable
3. Immerse the coin briefly—prolonged soaking offers no additional benefit
4. Agitate gently—swirl the acetone to help dissolve contaminants
5. Remove and air dry—never wipe or rub the treated surface
6. Repeat if necessary—multiple short treatments are far safer than one extended immersion

Critical warning: Acetone treatment on a PCGS-graded coin like this 1870 2 Cent Piece will almost certainly result in the coin being details-graded upon resubmission. With a population of 2 and 0 higher, this coin is simply too valuable to risk on unnecessary intervention.

Preventive Conservation: Protecting Your Investment

Optimal Storage Solutions for Bronze Coinage

Prevention always surpasses treatment in numismatic conservation. For high-grade bronze coins like this 1870 2 Cent Piece, proper storage represents the single most important conservation decision you’ll ever make.

Recommended storage materials include:

• Mylar flips—inert polyester that won’t react with copper surfaces
• Archival-quality cardboard holders—2x2s made from acid-free, sulfur-free materials
• Professional grading service holders—PCGS, NGC, and CAC holders provide excellent long-term protection
• Desiccant-containing environments—silica gel packets help control humidity in storage areas
• Stable temperature and humidity—avoid attics, basements, and other environmentally volatile locations

Materials to absolutely avoid:

• PVC flips and holders—the primary source of plasticizer damage
• Paper envelopes—acidic compounds attack copper over time
• Rubber bands and elastic—sulfur content causes rapid tarnish and corrosion
• Adhesive mounts—chemicals bond to surfaces and cause permanent damage
• Non-archival plastics—polyethylene and polypropylene are generally safe, but always verify composition

Environmental Monitoring and Maintenance

Proper conservation extends well beyond your initial storage decisions. Ongoing environmental monitoring ensures long-term protection:

• Regular visual inspection—examine coins periodically for early signs of damage before they become serious
• Humidity monitoring—maintain relative humidity below 50% in storage areas
• Temperature stability—avoid locations with significant temperature swings
• Air quality management—minimize exposure to pollutants and chemical vapors
• Documentation—photograph coins to track any changes over time

The Market Impact of Environmental Damage

How Conservation Affects Value

The 1870 2 Cent Piece in PCGS MS65+BN CAC represents a significant financial investment. Understanding how environmental damage affects market value helps collectors make informed conservation decisions—and avoid costly mistakes.

Value factors for condition census bronze coinage:

• Original surfaces—untreated, original surfaces command maximum premiums
• Eye appeal—attractive toning and minimal marks drive serious collector demand
• Population rarity—only 2 examples at this grade with none finer creates intense competition at auction
• Series popularity—Two Cent Pieces attract dedicated specialists who pay real money for quality
• Certification integrity—CAC approval confirms quality within the assigned grade, adding a layer of trust

Environmental damage can devastate value in several specific ways:

• Grade reduction—active corrosion or PVC damage typically results in details grades from the major services
• Details grading—designations like “cleaned,” “environmental damage,” or “corroded” destroy premium value overnight
• Market rejection—serious collectors avoid damaged coins regardless of rarity
• Conservation costs—professional treatment is expensive and never fully restores original surfaces

For a coin with a population of 2 and 0 higher, even minor environmental damage could reduce value by 50% or more. The investment in proper preventive conservation is trivial compared to what’s at stake.

Professional Conservation Resources

When to Seek Expert Help

While many conservation tasks suit knowledgeable collectors, certain situations demand professional intervention. I’d recommend consulting a professional conservator when:

• Active bronze disease is present—it requires specialized chemical treatment beyond what acetone can offer
• Severe PVC damage has occurred—advanced solvent treatment may be necessary
• The coin has exceptional value—it justifies professional conservation costs
• You’re uncertain about treatment—a professional assessment prevents costly mistakes
• Historical significance demands preservation—museum-quality treatment may be the right call

Professional numismatic conservators have access to treatments unavailable to most collectors:

• Mechanical reduction of corrosion—microscopic removal of damaged material under controlled conditions
• Chemical stabilization—benzotriazole (BTA) treatments specifically formulated for bronze disease
• Electrolytic reduction—careful removal of corrosion products using controlled electrical current
• Protective coatings—inert barriers that shield against future environmental attack
• Environmental chamber storage—controlled atmosphere preservation for the most sensitive specimens

Conclusion: Preserving Numismatic Heritage for Future Generations

The 1870 2 Cent Piece, PCGS MS65+BN CAC, Population 2 with 0 Higher, represents far more than a financial investment. This coin embodies a crucial period in American history—the post-Civil War era when the Two Cent Piece served as everyday currency for a nation rebuilding itself. Its exceptional preservation allows us to appreciate the artistry of James B. Longacre’s design and the technical achievement of nineteenth-century minting in ways that no photograph can fully capture.

As numismatic conservators, we bear a responsibility to preserve these tangible connections to our past. The environmental threats facing bronze coinage—bronze disease, PVC damage, destructive oxidation—are serious but manageable challenges. Through proper storage, environmental monitoring, and informed conservation decisions, we can ensure that coins like this remarkable 1870 2 Cent Piece survive for future generations to study and appreciate.

The forum discussion celebrating this coin’s beauty and rarity reminds us why conservation matters so deeply. When collectors invest in condition census pieces, they become stewards of numismatic heritage. Understanding environmental damage and implementing proper preservation techniques isn’t just good collecting practice—it’s our obligation to the historical record.

For owners of this exceptional 1870 2 Cent Piece and similar high-grade bronze coinage, I offer this final guidance: prioritize prevention over treatment, invest in proper storage, monitor environmental conditions religiously, and never hesitate to consult professionals when questions arise. The few hundred dollars spent on optimal conservation measures pales beside the thousands—perhaps tens of thousands—in numismatic value at risk.

Our coins have survived over 150 years of history. With proper care, they’ll survive another 150 and beyond, continuing to tell the story of American numismatics to collectors, historians, and enthusiasts yet unborn.

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