Verdigris and PVC: Saving GRADE REVEALED GTG 7 – Toned Morgan from Environmental Damage

Improper storage is the silent killer of numismatic value. Let’s identify the signs of environmental damage specific to this metal type.

As a numismatic conservator, I’ve spent decades examining coins that have survived wars, economic collapses, and generations of collectors who simply didn’t know better. The recent GRADE REVEALED GTG #7 – Toned Morgan thread gave us a fascinating case study: an 1885 Morgan Silver Dollar housed in an NGC “Fatty” holder, graded MS64. While the community debated the grade—with guesses ranging from MS62 to MS64—I want to shift the conversation to something far more critical: what happens to this coin if it’s improperly stored, and how do we prevent it?

Silver dollars like the 1885 Morgan are composed of 90% silver and 10% copper. That copper content is the Achilles’ heel. It’s what makes these coins susceptible to the very environmental damage we’ll explore today. Whether you’re a seasoned collector or just starting your journey, understanding these threats is essential to preserving your investment.

Understanding the Enemy: Why Silver-Copper Alloys Are Vulnerable

Before we dive into specific damage types, let’s establish why Morgan Silver Dollars are particularly at risk. The 90/10 silver-copper alloy is beautiful and historically significant, but it’s also chemically reactive in ways that pure gold or even copper-only coins are not.

Copper, when exposed to moisture, oxygen, and various chemical compounds, undergoes a series of reactions that produce different colored compounds:

• Cuprous oxide (Cu₂O) – Reddish-brown, often the first stage of oxidation
• Cupric oxide (CuO) – Black, more advanced oxidation
• Copper carbonate (CuCO₃) – Green, the classic “verdigris” or patina
• Copper chloride (CuCl₂) – Bright green, the hallmark of bronze disease

In my experience grading and conserving Morgans, I’ve seen every stage of this degradation. The 1885 Morgan in the GTG thread shows attractive toning—likely a result of sulfur compounds reacting with the silver surface over decades. But toning is a double-edged sword: it can be beautiful and stable, or it can be the precursor to more serious chemical damage.

Bronze Disease: The Silent Killer of Copper-Containing Coins

Let’s start with the most insidious threat: bronze disease. Despite its name, this condition affects any copper-containing alloy, including our beloved Morgan Silver Dollars.

What Is Bronze Disease?

Bronze disease is a cyclic, self-perpetuating corrosion process triggered by the presence of chloride ions on or within a coin’s surface. Here’s the chemical reaction in simplified terms:

CuCl₂ + H₂O → Cu₂O + 2HCl (hydrochloric acid)

The hydrochloric acid then attacks more copper, producing more copper chloride, which reacts with more water, producing more acid. The cycle continues indefinitely.

This is why bronze disease is so dangerous—it doesn’t stop on its own. Left unchecked, it will eventually consume the entire coin.

Identifying Bronze Disease on Morgan Dollars

On a Morgan Silver Dollar, bronze disease typically appears as:

• Bright green, powdery spots – Often mistaken for attractive toning at first glance
• Raised, crusty deposits – These can be gently probed; if they’re soft and powdery, it’s active corrosion
• Localized pitting beneath the green deposits – The surface underneath is being eaten away
• A musty or acidic smell – In advanced cases, you can actually smell the hydrochloric acid being produced

The 1885 Morgan in the GTG thread doesn’t appear to show signs of bronze disease in the posted images, but that’s precisely the point: prevention is far easier than treatment. If this coin were stored in a humid environment near the ocean (where salt air provides abundant chloride ions), or if it had been previously stored in PVC-laden holders that off-gassed chlorides, bronze disease could develop within months.

Treating Bronze Disease: A Conservator’s Protocol

If you suspect bronze disease on any Morgan Dollar, here’s the treatment protocol I recommend:

1. Isolate the coin immediately – Remove it from any holder and place it in a dry, chloride-free environment. Active bronze disease can spread to nearby coins.
2. Mechanical cleaning (gentle) – Using a soft wooden toothpick or bamboo skewer under magnification, carefully remove the powdery green deposits. Never use metal tools.
3. Chemical treatment with benzotriazole (BTA) – Soak the coin in a 3% BTA solution in ethanol for 24-48 hours. BTA forms a protective complex with copper ions, halting the corrosion cycle.
4. Thorough rinsing – Rinse multiple times in fresh, pure ethanol to remove all BTA residue.
5. Desiccation – Place the coin in a sealed container with silica gel desiccant for at least two weeks to ensure all moisture is removed.
6. Proper re-holder – Submit to NGC or PCGS for encapsulation in an inert, chloride-free holder.

Important note: If the pitting from bronze disease is deep and extensive, the coin’s grade will be permanently affected. NGC and PCGS will note “Environmental Damage” or “Corrosion” on the holder, significantly reducing market value. This is why early detection and prevention are paramount.

PVC Plasticizer Damage: The Hidden Threat in Old Holders

Now let’s talk about a threat that’s particularly relevant to the GTG thread: the coin is housed in an NGC “Fatty” holder. These older-style holders, while now collectible themselves, represent a transitional period in coin storage technology.

The PVC Problem Explained

PVC (polyvinyl chloride) was widely used in coin flips, albums, and early holders from the 1960s through the 1980s. The problem isn’t the PVC itself—it’s the plasticizers added to make PVC flexible. The most common plasticizer was (and in some cheap products, still is) diethylhexyl phthalate (DEHP).

Over time, these plasticizers migrate out of the PVC and deposit onto the coin’s surface. The result is:

• A hazy, greenish film – Often described as “PVC haze” or “PVC residue”
• Sticky or tacky surface texture – The plasticizer residue feels slightly sticky to the touch
• Irreversible damage if left too long – The plasticizer can etch into the metal surface, causing permanent dulling and discoloration

Why the “Fatty” Holder Matters

The NGC Fatty holders used in the late 1980s and early 1990s were a significant improvement over PVC flips, but they weren’t perfect. Early versions used a gasket material that, in rare cases, could off-gas sulfur compounds. More importantly, if this 1885 Morgan was previously stored in a PVC flip before being encapsulated, the PVC damage may already be present beneath the toning.

In my experience, I’ve seen Morgans that looked beautifully toned in PVC flips, only to reveal extensive PVC damage once the toning was carefully removed. The toning essentially “hid” the plasticizer residue, making the coin appear healthier than it actually was.

Detecting and Treating PVC Damage

Here’s how I assess PVC damage during conservation:

1. Visual inspection under raking light – PVC haze appears as a uniform, slightly greenish film that doesn’t follow the natural toning patterns of the coin
2. UV fluorescence – PVC residue often fluoresces differently than natural toning under ultraviolet light
3. Acetone test – A small drop of pure acetone on an inconspicuous area will dissolve PVC residue but won’t affect natural toning or the metal surface

For treatment, I use a multi-step acetone protocol:

• First dip: Pure acetone (reagent grade, not nail polish remover) for 5-10 minutes
• Gentle agitation: Using a soft cotton swab, lightly wipe the surface to remove dissolved plasticizer
• Second dip: Fresh acetone for another 5 minutes to remove any remaining residue
• Final rinse: A third bath in fresh acetone to ensure complete removal
• Air dry: Allow the coin to air dry in a dust-free environment—never use heat or compressed air

Critical warning: Acetone will NOT remove natural toning, mint luster, or the metal itself. It will, however, remove artificial toning, PVC residue, oils, and most organic contaminants. This is why acetone dips are the gold standard in numismatic conservation—but they should only be performed by experienced professionals or under expert guidance.

Oxidation and Toning: The Fine Line Between Beauty and Damage

The 1885 Morgan in the GTG thread is described as “toned,” and the community clearly appreciates its aesthetic appeal. But as a conservator, I need to explain the complex relationship between toning, oxidation, and long-term coin health.

The Chemistry of Silver Toning

Silver toning is primarily the formation of silver sulfide (Ag₂S) on the coin’s surface. This occurs when silver reacts with sulfur-containing compounds in the environment:

4Ag + 2H₂S + O₂ → 2Ag₂S + 2H₂O

The thickness of the silver sulfide layer determines the color we see, due to thin-film interference:

• Thin layer (30-50 nm): Yellow or gold
• Medium layer (50-100 nm): Orange, red, or magenta
• Thick layer (100-200 nm): Blue, green, or purple
• Very thick layer (200+ nm): Gray or black (this is where toning becomes problematic)

When Toning Becomes Damage

Not all toning is created equal. Here’s how I differentiate between stable, attractive toning and dangerous oxidation:

Stable toning characteristics:

• Smooth, even color transitions
• No raised or crusty deposits
• No pitting visible beneath the toning
• Consistent with the coin’s storage history (e.g., album toning, envelope toning)

Dangerous oxidation characteristics:

• Uneven, blotchy discoloration
• Raised deposits or crusty texture
• Pitting or roughness beneath the discoloration
• Active spreading over time (compare photos taken months apart)
• Acidic smell when the coin is warmed slightly

The 1885 Morgan’s toning appears to be stable based on the images—it shows the kind of gradual, rainbow-like color progression that suggests decades of slow, even exposure to low levels of sulfur compounds. This is the “good” kind of toning that collectors pay premiums for.

The Copper Oxidation Problem

Remember that 10% copper content? While silver forms relatively stable silver sulfide, copper forms a variety of compounds that can be far more problematic:

• Cuprous oxide (reddish-brown): Relatively stable, but indicates ongoing oxidation
• Cupric oxide (black): More advanced oxidation, can obscure design details
• Copper carbonate (green): Indicates exposure to carbon dioxide and moisture—a warning sign
• Copper chloride (bright green, powdery): Bronze disease—the most serious threat

On Morgan Dollars, copper oxidation often appears first in the protected areas of the design—within the letters, around the stars, and in the recesses of Liberty’s hair. These areas trap moisture and contaminants, creating micro-environments where oxidation accelerates.

Proper Chemical Conservation: The Acetone Dip and Beyond

Let’s discuss the most common and effective chemical conservation technique: the acetone dip. This is the first line of defense for most surface contaminants on silver coins.

Why Acetone Works

Acetone (CH₃COCH₃) is a powerful organic solvent that dissolves:

• PVC plasticizer residue
• Oils and fingerprints
• Adhesives from stickers or tape
• Most artificial toning compounds
• Grease and organic contaminants

Crucially, acetone does NOT react with silver, copper, or their stable compounds (silver sulfide, copper oxide). This makes it safe for use on Morgan Dollars when applied correctly.

The Proper Acetone Dip Protocol

Here’s the exact protocol I use in my conservation practice:

1. Use only reagent-grade acetone (99.5%+ purity) – Hardware store acetone contains water and other additives that can cause spotting. Nail polish remover contains oils, fragrances, and conditioners that will make things worse.
2. Use glass containers only – Acetone dissolves many plastics, which will contaminate both the solvent and the coin.
3. Submerge the coin completely – Partial dipping creates visible lines that are nearly impossible to remove.
4. Agitate gently – Swirl the container slowly for 30-60 seconds. Do not use ultrasonic cleaners, as they can damage the coin’s surface.
5. Allow 5-10 minutes of soaking time – This gives the acetone time to penetrate and dissolve contaminants.
6. Remove and air dry – Place the coin on a clean, lint-free surface in a dust-free environment. Acetone evaporates quickly (boiling point: 56°C/133°F), so drying takes only a few minutes.
7. Repeat if necessary – For heavy PVC contamination, multiple dips in fresh acetone may be required.

What Acetone Cannot Do

It’s equally important to understand acetone’s limitations:

• It cannot remove natural toning – Silver sulfide is insoluble in acetone. If the toning is natural, it will remain.
• It cannot reverse pitting or corrosion – Once the metal surface is damaged, no chemical treatment can restore it.
• It cannot remove bronze disease – BTA treatment is required for active chloride corrosion.
• It cannot improve the grade – Acetone cleaning removes contaminants but doesn’t add luster or remove wear.

Preventive Storage: Protecting Your Morgan Dollars for Generations

The best conservation is prevention. Here’s how I recommend storing Morgan Silver Dollars to avoid all the damage types we’ve discussed:

Ideal Storage Conditions

• Temperature: 65-72°F (18-22°C), stable with minimal fluctuation
• Relative humidity: 30-40% (use silica gel or a dehumidifier)
• Air quality: Low sulfur, low chloride, filtered if possible
• Light: Minimal UV exposure (no direct sunlight, use UV-filtering glass if displaying)

Approved Storage Materials

Only use materials that have been tested and approved for long-term coin storage:

• NGC or PCGS holders – Inert, archival-quality encapsulation
• Mylar (polyester) flips – Specifically labeled as “archival” or “museum quality”
• Acid-free cardboard holders – 2x2s with Mylar windows
• Archival-quality albums – Capital Plastics, Whitman (modern versions)
• Interception Technology holders – Actively absorb corrosive gases

Materials to Absolutely Avoid

• PVC flips or holders – The number one cause of preventable coin damage
• Rubber bands – Sulfur compounds migrate into the metal surface
• Paper envelopes (non-archival) – Acidic paper causes spotting and corrosion
• Wooden cabinets (unsealed) – Off-gas acetic acid and other corrosive compounds
• Adhesive labels or stickers – Leave residue that’s difficult to remove
• Cotton gloves (for handling) – Can catch on coin edges; use nitrile gloves instead

Case Study: The 1885 Morgan Silver Dollar

Let’s bring this all together with the specific coin from the GTG thread. The 1885 Morgan Silver Dollar is a particularly interesting case for conservation purposes.

Historical Context

The 1885 Morgan Dollar was struck at three mints:

• Philadelphia (no mint mark): 17,787,000 business strikes
• New Orleans (O): 9,185,000 business strikes
• San Francisco (S): 1,497,000 business strikes

With a mintage of nearly 28.5 million coins, the 1885 is relatively common in lower grades but becomes scarce in MS65 and above. The coin in the GTG thread, graded MS64, represents a solid mid-grade example with attractive toning.

Conservation Assessment

Based on the images posted in the thread, here’s my professional assessment:

• Toning: Appears to be natural, stable toning with good color progression. The rainbow-like hues suggest long-term, even exposure to low levels of sulfur compounds—likely from storage in a paper envelope or album page.
• Surface quality: The coin shows good luster beneath the toning, with no visible pitting, corrosion, or PVC damage in the images.
• Holder: The NGC Fatty holder is appropriate for this coin. While not as advanced as modern NGC holders, it provides adequate protection if stored properly.
• Grade justification: The MS64 grade appears appropriate. The toning is attractive enough to potentially add a “premium” designation, and the surfaces appear clean with no significant marks visible in the images.

Long-Term Preservation Recommendations

For the owner of this specific coin, I recommend:

1. Do not attempt to “improve” the toning – The natural toning adds both aesthetic appeal and market value. Removing it would be counterproductive.
2. Store the holder in a cool, dry place – Avoid attics, basements, or garages where temperature and humidity fluctuate.
3. Monitor annually – Check for any signs of new toning, spotting, or corrosion. Early detection is key.
4. Consider re-holdering – If the Fatty holder shows any signs of deterioration (clouding, cracking, or off-gassing), submit to NGC for re-holdering in a modern holder.
5. Document the coin’s condition – Take high-resolution photographs annually to track any changes over time.

When to Seek Professional Conservation

Not every coin needs professional treatment, but certain situations absolutely warrant expert intervention:

Seek professional conservation if you observe:

• Bright green, powdery deposits (possible bronze disease)
• Active spreading of discoloration over weeks or months
• Sticky or tacky surface texture (PVC contamination)
• Visible pitting or roughness on the coin’s surface
• Any coin that has been recovered from the ground or water
• Coins stored in PVC holders for extended periods (10+ years)

Do NOT attempt DIY conservation if:

• The coin is valuable (above $500 retail)
• You’re unsure what type of damage you’re seeing
• The toning appears natural and attractive
• You don’t have access to proper materials and workspace

When in doubt, consult a professional conservator or submit the coin to NGC or PCGS for evaluation. The cost of professional conservation is almost always less than the value lost by improper treatment.

Conclusion: Preserving Numismatic Heritage

The 1885 Morgan Silver Dollar from the GRADE REVEALED GTG #7 thread is more than just a coin—it’s a tangible piece of American history. Struck during the Gilded Age, it witnessed the closing of the American frontier, the rise of industrial capitalism, and the transformation of the United States into a global power. Every Morgan Dollar carries this historical weight, and it’s our responsibility as collectors and custodians to preserve these artifacts for future generations.

The environmental threats we’ve discussed—bronze disease, PVC damage, and harmful oxidation—are all preventable with proper knowledge and storage practices. The good news is that the numismatic community has never been better informed about conservation. Modern holders, archival storage materials, and professional conservation services make it easier than ever to protect your collection.

As I tell every collector who walks through my door: the best time to start proper conservation was twenty years ago. The second-best time is today. Whether you own a single Morgan Dollar or a collection worth millions, the principles are the same. Store properly, monitor regularly, and seek professional help when needed.

The 1885 Morgan in MS64 with attractive toning is a beautiful coin that deserves to be preserved in its current state. With proper care, it will continue to tell its story for another 139 years—and beyond. That’s the true value of numismatic conservation: not just protecting an investment, but safeguarding a piece of our shared heritage.

Remember, every coin in your collection is a time capsule. Treat it with the respect it deserves, and it will reward you with both historical significance and lasting value.

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