Verdigris and PVC: Saving Your Coins from Environmental Damage — Lessons from JA’s CAC Review Process

Let’s talk about the silent killer of numismatic value: environmental damage. If you’ve ever pulled a coin out of an old album only to find it corroded, hazy, or sticky, you already know the heartbreak. Let’s identify the signs specific to each threat—and more importantly, learn how to fight back.

I’ve spent decades as a numismatic conservator, examining, preserving, and evaluating coins across every metal type and denomination you can name. If there’s one truth I’ve learned, it’s this: the single most preventable cause of value destruction in our hobby is environmental damage. Watching John Albanese work through his CAC evaluation process in that now-famous video from Cabbage Coins was a genuine masterclass—not just in grading philosophy, but in how environmental factors quietly erode a coin’s surface, eye appeal, and ultimately its market value. The forum discussion it sparked confirmed something I’ve long observed: collectors and even experienced dealers often fail to recognize the subtle fingerprints of environmental damage until it’s too late.

In this article, I’ll walk you through the most common forms of environmental damage I encounter in my conservation work—bronze disease, PVC plasticizer damage, oxidation, and the role of proper chemical conservation—and I’ll share actionable guidance drawn from the very scenarios JA discussed in that video. Whether you’re submitting to CAC, building a type set, or preserving a family heirloom, understanding these threats is essential to protecting your collection’s numismatic value.

What JA’s CAC Review Reveals About Surface Preservation

In the video, JA reviews 400 to 500 coins per day. Of those, roughly a dozen require consultation with his grading team—the borderline cases where a coin could “go either way on any given day.” What struck me most was his emphasis on the etiology of surface marks. As one forum member astutely observed, CAC’s primary concern isn’t just eye appeal—it’s understanding why a mark or discoloration exists. That distinction is the dividing line between a coin that has been naturally preserved in something close to mint condition and one that has been quietly ravaged by its environment.

When JA examined the 1898 MS66 Barber Quarter at the 39:12 timestamp, he was genuinely on the fence about awarding the coveted CAC bean. The coin exhibited dark areas where toning had, in the words of one forum commentator, “gone too far.” That kind of dark, lifeless toning is frequently the end result of prolonged environmental exposure—and it’s one of the first things I look for when a coin arrives at my conservation bench. It tells a story, but not a good one.

“I almost fell out of my chair when he kept recommending dipping/acid in certain situations (done by professionals, of course).” — Forum member Baylor8670

This reaction is common among collectors who’ve been taught that all cleaning is sacrilege. But as JA correctly emphasizes, there is a vast difference between amateur “cleaning” and professional conservation. Let me explain the specific threats and how each one should be addressed—because the right intervention can mean the difference between a rare variety with strong collectibility and a coin that’s essentially worthless.

Bronze Disease: The Silent Destroyer of Copper and Bronze Coins

If I had to name the single most insidious form of environmental damage affecting copper, bronze, and brass coins, bronze disease would be it without hesitation. I’ve examined thousands of coins in my career, and bronze disease is the condition that makes me wince most often—because it’s almost always progressive, almost always preventable, and almost always misunderstood by the collector who brings it to me.

What Is Bronze Disease?

Bronze disease is a form of corrosion caused by the interaction of chlorides (typically from salt, humidity, or handling with bare hands) with copper alloys. It manifests as bright green, powdery or crystalline spots on the surface—often mistaken by inexperienced collectors for ordinary verdigris or attractive toning. It is not. Bronze disease is an active, ongoing chemical reaction that will continue to eat through the metal until it is arrested or until the coin is effectively destroyed.

How to Identify Bronze Disease

In my conservation practice, I look for the following markers:

• Bright green, almost fluorescent spots that appear raised above the coin’s surface
• Powdery or crusty texture—if you touch the area with a fine probe and it crumbles or leaves a residue, that’s a strong indicator
• Localized outbreaks—bronze disease rarely covers the entire coin; it tends to cluster in areas where moisture or contaminants were trapped, such as near the rim or in recessed design elements
• Progressive spread—if you’ve stored a coin for a year and the green spots have visibly enlarged or multiplied, you have an active case that demands immediate attention

Why It Matters for Grading and Value

Bronze disease is a death sentence for high-grade coins. A Mint State copper coin with active bronze disease will not sticker at CAC—and frankly, it shouldn’t. The structural integrity of the metal is compromised, and no amount of aesthetic appeal can offset that fundamental problem. Even at lower grades where such damage might be expected, active bronze disease signals to knowledgeable buyers that the coin requires immediate intervention, which significantly depresses market value and collectibility.

Treatment and Prevention

Treatment involves a multi-step process I perform regularly in my conservation lab:

1. Mechanical removal of the bulk corrosion using fine instruments under magnification
2. Chemical stabilization using a benzotriazole (BTA) solution to inhibit further chloride activity
3. Thorough rinsing and drying—this step is critical and often botched by amateurs who rush the process
4. Sealed storage in an inert, humidity-controlled environment

Prevention is far simpler and far less costly: store copper and bronze coins in a dry environment (below 40% relative humidity is ideal), never handle them with bare hands, and avoid any storage material that off-gasses chlorides or other reactive compounds. A small investment in proper holders today saves you from heartbreak tomorrow.

PVC Plasticizer Damage: The Hidden Cost of Old Flips

One forum member joked, “Now I know that all of my coins are probably covered in PVC unless they CAC’d.” The humor masks a genuine and widespread problem that I see in my conservation practice on a weekly basis. Polyvinyl chloride (PVC) plastic—found in older coin flips, soft vinyl holders, and certain album pages—releases plasticizers over time that chemically bond to a coin’s surface. The result is a greenish, sticky, or hazy film that can permanently damage the metal and destroy original luster if left untreated.

Recognizing PVC Damage

I’ve seen PVC damage on coins of every denomination and metal type, but it’s most visually dramatic on silver and copper. Here’s what to watch for:

• Greenish or bluish-green haze that appears to sit within the coin’s surface rather than on top of it—this is the telltale sign
• Sticky or tacky feel when the coin is handled (though I always recommend handling coins by the rim with clean cotton gloves regardless)
• Uneven distribution—PVC damage often mirrors the pattern of contact with the offending plastic, creating distinctive streaks or patches that follow the flip’s edges
• Progressive worsening—PVC damage is cumulative. A coin that shows mild haze today may develop deep, irreversible staining within a year if left in the same holder. I cannot stress this enough: time is not on your side with PVC.

Why CAC Rejects PVC-Damaged Coins

When JA evaluates a coin for a CAC sticker, surface integrity is paramount. PVC damage represents a chemical alteration of the coin’s original surface—the very surface that PCGS, NGC, or CACG graded. Even if the underlying coin is technically the grade assigned, PVC contamination introduces an element of uncertainty that CAC is unwilling to overlook. A coin with PVC film will almost certainly be rejected, and for good reason: the damage may continue to progress even after encapsulation, undermining the very quality that the sticker is meant to guarantee.

Acetone Baths: The Conservative Conservator’s Best Friend

This is where chemical conservation—specifically, acetone baths—becomes essential. And this is precisely what JA alludes to in the video when he discusses the benefits of professional conservation.

Acetone (pure, reagent-grade, not nail polish remover) is one of the safest and most effective tools in a conservator’s arsenal for addressing PVC damage. Here’s why and how it works:

• Acetone is a solvent that dissolves PVC residue without reacting with the coin’s metal. It lifts the plasticizer film cleanly away from the surface, preserving the original luster underneath.
• The process involves submerging the coin in a bath of pure acetone for a period ranging from a few seconds to several minutes, depending on the severity of contamination.
• After the bath, the coin is rinsed in a second bath of clean acetone to remove any dissolved residue, then allowed to air-dry on a clean, lint-free surface.
• Critical warning: The acetone must be 100% pure. Nail polish remover and hardware-store acetone frequently contain oils, fragrances, or other additives that will leave their own residue on the coin—potentially making the problem worse than when you started.

In my experience, a properly executed acetone bath can dramatically improve a coin’s appearance and surface integrity without any loss of original metal or luster. It is not “cleaning” in the pejorative sense—it is the removal of a foreign contaminant that was never part of the coin to begin with. The coin’s true eye appeal, its original strike details, and its honest patina remain intact.

“I was pleasantly surprised by how much John stresses the benefits of conservation. The coin with the dirt all over the obverse made me cringe on how bad it looked and how easy it is to conserve.” — Forum member Baylor8670

This observation hits the nail on the head. The “dirty dollar” that Tony from Cabbage Coins submitted—the one that got “shellacked in the most polite way possible”—is a perfect case study. Dirt, grime, and surface contamination are not part of a coin’s character or provenance. They are obstacles to accurate evaluation, and their removal through proper conservation can reveal the true quality of the underlying surface. Sometimes what looks like a problem coin is actually a hidden gem waiting to be rediscovered.

Oxidation and Toning: When Natural Processes Go Wrong

Oxidation is the broad chemical process by which metals react with oxygen and other environmental agents. All coins oxidize to some degree—that’s what creates toning. And toning, when it develops slowly and evenly, can be breathtakingly beautiful and highly desirable. But oxidation is a process that exists on a spectrum, and the environmental conditions under which it occurs determine whether the result is an attractive patina that enhances eye appeal or destructive corrosion that obliterates it.

The Spectrum of Oxidation

In my conservation work, I categorize oxidation into three broad levels:

1. Beneficial toning—thin, even, naturally developed layers of oxidation that enhance a coin’s eye appeal. Think of the rainbow toning on a Morgan dollar that’s been stored in a cloth bank bag for a century. This is oxidation at its most aesthetically pleasing, and it can significantly boost both numismatic value and collectibility.
2. Neutral oxidation—mild, even darkening that doesn’t significantly detract from eye appeal but doesn’t enhance it either. Many brown copper coins and evenly toned silver pieces fall into this category. The coin is honest and original, just not visually exciting. It retains its integrity and its story.
3. Destructive oxidation—thick, uneven, or chemically aggressive oxidation that obscures design details, creates unsightly dark patches, or actively compromises the metal’s surface. This is what JA was describing when he noted the dark areas on the 1898 Barber Quarter where toning had “gone too far.” At this stage, the coin’s eye appeal and market value have both suffered real damage.

Environmental Factors That Accelerate Destructive Oxidation

Several environmental conditions push oxidation from the beneficial or neutral categories into the destructive:

• High humidity—moisture is the primary accelerator of destructive oxidation. Coins stored in basements, attics, or coastal environments are at particular risk, and I’ve seen devastating results from all three.
• Temperature fluctuations—repeated cycles of heating and cooling cause condensation on coin surfaces, creating micro-environments where oxidation accelerates dramatically.
• Airborne pollutants—sulfur compounds (from rubber, certain papers, and industrial environments) react with silver to form silver sulfide, the black tarnish that can become deeply embedded over time and nearly impossible to reverse.
• Contact with reactive materials—cardboard, newspaper, wool, and certain plastics all off-gas chemicals that accelerate oxidation on coin surfaces. These materials are everywhere in typical household storage, which is exactly why inherited collections so often arrive at my bench in poor condition.

The 1872-S Seated Dollar: A Case Study

One forum member expressed a desire to crack out an 1872-S Seated dollar to “make it look so much nicer.” This is exactly the kind of impulse that gives conservators like me pause. That coin’s “crust”—its natural surface patina developed over 150 years—is part of its identity, its provenance, and its market value. Removing it in pursuit of a brighter appearance is not conservation; it’s alteration. And the numismatic community will notice.

However, the same forum member noted “two obverse mud stains” that detracted from the coin’s appeal. This is a scenario where targeted, professional conservation can make a meaningful difference. Removing encrusted foreign material (mud, dirt, grease) that was never part of the coin’s natural surface is fundamentally different from stripping away original patina. The key is knowing the difference—and having the skill and restraint to act only where appropriate. When done correctly, this kind of intervention preserves the coin’s honest character while removing the distractions that obscure its true quality.

Proper Chemical Conservation: When and How to Intervene

JA’s willingness to recommend dipping and acid treatment in certain situations was, as one forum member noted, surprising to many viewers. But for those of us in the conservation community, it’s simply good practice applied judiciously. Let me outline the principles I follow—and that I believe JA would endorse—when considering chemical intervention on any coin.

The Conservator’s Hierarchy of Intervention

Not every coin needs chemical treatment. In fact, most don’t. I follow a hierarchy of intervention that prioritizes the least invasive approach first:

1. Mechanical cleaning only—gentle removal of loose debris using soft brushes, wooden picks, or distilled water rinses. This is appropriate for surface dirt, dust, and other loosely adhered contaminants that haven’t bonded to the metal.
2. Distilled water soak—for more stubborn deposits, a soak in distilled water (never tap water, which contains chlorine and dissolved minerals that can cause their own damage) can soften and lift contaminants without any chemical interaction with the metal.
3. Acetone bath—as described above, for PVC residue, adhesive contamination, and other organic films. This is the workhorse of numismatic conservation and the single most useful tool in my practice.
4. Controlled acid dip—for silver coins with heavy sulfide tarnish that cannot be removed by gentler means. This should only be performed by experienced professionals using precisely timed immersions in a silver dip solution (typically a thiourea-based or dilute acid formula). Over-dipping strips away original luster and leaves the coin with an artificial, “washed-out” appearance that is immediately recognizable to graders and experienced collectors. It’s a line you do not want to cross.
5. Electrolytic reduction—a last resort for severely corroded copper or bronze coins, typically reserved for specimens of significant historical importance where the alternative is total loss. This process is aggressive and irreversible, and it fundamentally alters the coin’s surface. I use it sparingly and only when the coin’s survival is at stake.

What NOT to Do

Over the years, I’ve seen the consequences of well-intentioned but misguided “cleaning” attempts that would make your stomach turn. Here is my list of absolute prohibitions:

• Never use abrasive polishes (Brasso, silver polish, etc.)—these remove original metal and leave microscopic scratches that destroy luster permanently. I’ve seen otherwise Mint State coins reduced to damaged goods by a single afternoon of enthusiastic polishing.
• Never use vinegar, lemon juice, or household acids—these are uncontrolled, unpredictable, and leave the coin vulnerable to accelerated future corrosion. The damage is often invisible at first but devastating over time.
• Never rub a coin with your fingers—the oils and salts in human skin are among the most common causes of both PVC-like spotting and bronze disease on copper coins. Handle everything by the rim, preferably with clean cotton gloves.
• Never “dip” a coin without understanding the consequences—a proper dip is measured in seconds, not minutes, and requires immediate thorough rinsing and drying. This is professional work, not a weekend project.

Storage Best Practices: Prevention Is Worth a Pound of Cure

The most effective conservation strategy is preventing damage before it occurs. Based on my experience examining coins from every type of storage environment imaginable—from pristine museum vaults to shoeboxes in flooded basements—here are my firm recommendations:

Ideal Storage Conditions

• Relative humidity below 40%—use silica gel packets or a dehumidifier in your storage area. This single step prevents more environmental damage than any other action you can take.
• Stable temperature—avoid attics, garages, and anywhere with significant temperature swings. Consistency is key.
• Inert storage materials only—Mylar flips (never PVC), archival-quality cardboard holders, and acid-free tissue paper. Spend the extra few cents per coin; it’s the cheapest insurance you’ll ever buy.
• Airtight encapsulation—PCGS, NGC, and CACG holders provide excellent protection once the coin is properly graded and sealed. For high-value pieces, encapsulation should be a priority.
• Avoid rubber and sulfur-containing materials—rubber bands, rubber gaskets, and certain papers and fabrics off-gas sulfur compounds that tarnish silver. I’ve seen entire collections ruined by a single rubber band left in a box.

What to Do If You Inherit a Collection

Many of the worst cases of environmental damage I see come from inherited collections that were stored for decades in suboptimal conditions—shoeboxes in attics, paper envelopes in basements, or old albums with PVC-laden pages. If you’ve recently acquired such a collection, here’s my step-by-step guidance:

1. Do not attempt to clean anything yourself—improper cleaning can reduce a coin’s value by 50% or more overnight. I’ve witnessed this heartbreak more times than I can count.
2. Separate coins by metal type—copper, silver, and gold have different storage needs and different vulnerabilities. Keeping them together can accelerate cross-contamination.
3. Remove all PVC flips immediately—transfer coins to Mylar flips or archival holders. Every day a coin spends in PVC is another day of potential damage.
4. Assess for bronze disease—examine all copper and bronze coins under magnification for signs of active corrosion. Early detection is everything.
5. Consult a professional conservator—for any coin you believe may be valuable or historically significant, professional assessment before any intervention is essential. A small consultation fee can save you from a catastrophic mistake.

How Environmental Damage Affects CAC Submissions

The forum discussion made clear that watching JA’s evaluation process changed how many collectors plan to approach CAC submissions. This is exactly the right takeaway. CAC’s standards are rigorous, and for good reason: the CAC sticker represents a guarantee of quality that the market trusts. Coins with environmental damage—whether from PVC, bronze disease, destructive oxidation, or improper cleaning—will not meet those standards. Period.

Before submitting to CAC, I recommend working through this checklist carefully:

• Examine the coin under 5x–10x magnification for any signs of PVC film, bronze disease, or surface contamination. What’s invisible to the naked eye can be glaringly obvious under magnification.
• Check for “processed” surfaces—if the coin has been dipped, whizzed, or otherwise altered, CAC will likely detect it. Honesty about a coin’s history is always the best policy.
• Assess toning honestly—is the toning natural and attractive, or is it the result of environmental damage? Dark, mottled, or uneven toning is a red flag that warrants closer inspection.
• Consider professional conservation before submission—if the coin has surface contamination that can be safely removed, doing so before submission may mean the difference between a bean and a rejection. Timing matters.
• Be realistic about the grade—as JA noted, some coins legitimately fall between grades. A coin that could be a 63 or a 64 but will never be a 65 should be evaluated on its own merits, not wishful thinking. Submitting a coin that falls short wastes your money and your time.

Conclusion: Preservation Is Part of the Hobby

What I found most encouraging about the forum discussion surrounding JA’s CAC video was the genuine enthusiasm for learning. Collectors who had never considered the science of conservation were suddenly asking the right questions: What is that green spot? Why is my coin hazy? Should I dip it? Can I remove that dirt without damaging the surface?

These are the questions that separate casual collectors from serious numismatists. The coins we preserve today—whether they’re 1898 Barber Quarters, 1872-S Seated Liberty Dollars, or 1912-S Liberty Nickels—are irreplaceable artifacts of American history. Their value lies not just in their rarity or grade, but in the integrity of their surfaces and the stories those surfaces tell. A coin’s provenance is written in its patina, its strike, and the marks it has accumulated over decades or centuries of existence. Our job is to honor that story, not erase it.

Environmental damage is not inevitable. Bronze disease can be prevented with proper humidity control. PVC damage can be avoided by using inert storage materials. Destructive oxidation can be minimized through stable, clean storage conditions. And when damage has already occurred, professional conservation—including acetone baths, controlled acid treatments, and careful mechanical cleaning—can often restore a coin to a condition that honors both its history and its numismatic value.

As JA demonstrated in that video, the best evaluators in our hobby understand that a coin’s surface is a record of its life. Our job as collectors, dealers, and conservators is to ensure that record is preserved—not just for the next grading submission, but for the next generation of numismatists who will hold these pieces and wonder about the hands and environments they’ve passed through.

Store carefully. Handle minimally. And when in doubt, consult a professional. Your coins—and their CAC stickers—will thank you.

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