Verdigris and PVC: Saving Your Precious Metal Medallions from Environmental Damage — A Conservator’s Guide to Bronze Disease, Oxidation, and Chemical Conservation

Improper storage is the silent enemy of numismatics. Let’s identify the signs of environmental damage specific to this metal type.

As a numismatic conservator with over two decades of experience examining, grading, and preserving coins and medals across every metal type — from ancient bronzes to modern gold commemoratives — I can tell you that environmental damage is the single most underestimated threat to a collection’s long-term value. Whether you’re holding a PF70 Ultra Cameo gold medallion or a circulated copper piece, the enemies are the same: moisture, airborne chemicals, improper plastics, and neglect. Today, I want to walk you through the specific types of environmental damage that affect precious metal items like the Trump/UFC “Freedom 250” gold and silver medallions currently being marketed at premium prices. More importantly, I want to show you exactly how to identify, prevent, and in some cases reverse the damage.

Why Environmental Damage Matters More Than You Think

When collectors think about damage, they often focus on the obvious — scratches, dents, wear from circulation. But environmental damage is insidious. It works slowly, often invisibly, and by the time you notice it, the chemical changes to the metal’s surface may be irreversible.

I’ve examined thousands of coins and medals that were stored in what the owner believed were “safe” conditions, only to find active bronze disease, PVC contamination, or deep oxidation that had silently destroyed the original surface. The eye appeal — that crucial first impression that drives collectibility — was gone before the owner ever realized anything was wrong.

This is especially relevant for modern commemorative medallions like the Trump/UFC Freedom 250 series. These are being sold at significant premiums — the 1 oz gold medallion at nearly $12,000, silver versions starting around $250 — and buyers are being told they are receiving NGC-graded PF70 Ultra Cameo specimens. At those price points, proper conservation isn’t optional; it’s essential. A single episode of improper storage can turn a $12,000 medallion into a piece worth only its melt value.

Understanding the Metals: Gold, Silver, and Their Vulnerabilities

Before we dive into specific damage types, it’s important to understand what we’re working with. The Trump/UFC medallions are offered in two primary metals:

• Gold (Au): The 1 oz and 1/10 oz gold medallions are struck in .9999 fine gold. Gold is the most chemically resistant of all precious metals — it does not oxidize, tarnish, or corrode under normal conditions. However, this does not make it immune to all environmental damage. Surface contamination can still dull the luster and compromise the numismatic value of even the finest gold piece.
• Silver (Ag): The 1 oz and 5 oz silver medallions are struck in .999 fine silver. Silver is far more reactive than gold and is highly susceptible to sulfur compounds in the atmosphere, which cause tarnish (silver sulfide) and, in severe cases, irreversible surface corrosion that can permanently diminish both strike detail and eye appeal.

It’s also worth noting that many modern commemorative items — particularly those with antique or “bronze-style” finishes, or those that include bronze display elements — can be affected by the most destructive form of environmental damage known to numismatics: bronze disease.

Bronze Disease: The Silent Killer

Bronze disease is, in my professional experience, the most feared and least understood form of environmental damage among collectors. Despite its name, it doesn’t only affect bronze — it can attack any copper alloy, including the copper-nickel cladding found on some modern coins, and it can spread to adjacent metal surfaces in a collection. I’ve seen it destroy the provenance and value of pieces that took decades to acquire.

What Causes Bronze Disease?

Bronze disease is caused by the presence of chloride ions in contact with copper or copper-alloy surfaces in the presence of moisture and oxygen. The chlorides can come from a variety of sources:

• Handling with bare hands (sweat contains sodium chloride)
• Storage in wooden cabinets or drawers (wood off-gasses acetic acid and can trap chlorides)
• Proximity to saltwater or coastal environments
• Contamination from PVC plastic holders (which release hydrochloric acid as they degrade)
• Even certain types of tissue paper or cardboard used in original packaging

How to Identify Bronze Disease

The telltale sign of bronze disease is the appearance of bright green, powdery or crusty spots on the metal surface. These spots are copper chloride hydroxide compounds — essentially, the metal is being eaten away from the inside out. In my conservation work, I’ve seen cases where a coin that looked perfectly fine on one examination developed active bronze disease spots within six months of being stored in a humid environment.

Key identification markers include:

1. Bright green spots that are raised above the surface — not flat discoloration, but actual crusty or powdery deposits
2. Progressive spread — the spots grow over time if left untreated
3. Pitting beneath the spots — when the green crust is carefully removed, you’ll find irregular pits in the metal surface
4. A faint acidic smell — active bronze disease often has a subtle but detectable acidic odor when examined closely

Treatment and Prevention

Treating bronze disease requires patience and precision. The standard conservation protocol involves:

1. Mechanical removal of the visible green deposits using a wooden pick or fine brass brush under magnification
2. Chemical treatment with a 5% sodium sesquicarbonate solution to neutralize the chloride ions — this is a slow process that can take weeks or even months for severe cases
3. Rinsing and drying — thorough rinsing with distilled water followed by complete drying
4. Sealing — application of a protective coating such as Renaissance Wax or Incralac to prevent recurrence

For prevention, I recommend storing any copper-alloy or bronze items in a controlled environment with relative humidity below 40%, using only archival-quality, PVC-free holders, and never handling the metal surfaces with bare hands. This is especially critical for any rare variety or mint-condition specimen where surface integrity directly determines collectibility.

PVC Plasticizer Damage: The Clear Holder Curse

If there is one thing I wish every collector understood before purchasing their first coin, it is the danger of PVC. Polyvinyl chloride — the soft, flexible plastic used in many coin flips, folders, and display cases — is one of the most destructive storage materials ever used in numismatics.

How PVC Damages Coins and Medallions

PVC is inherently unstable. Over time, it releases plasticizers (primarily phthalates) and, critically, hydrochloric acid gas. When a coin or medal is enclosed in a PVC holder, these chemicals build up in the micro-environment between the plastic and the metal surface. The result is a characteristic greenish, sticky or tacky film on the metal that is extremely difficult to remove and that causes permanent surface damage.

I’ve seen countless examples of this in my conservation practice. A collector brings me a coin that was stored in a PVC flip for 20 years, and the surface has a greenish haze that cannot be fully removed without damaging the underlying metal. On silver items, the damage can be even more severe, as the hydrochloric acid accelerates sulfide tarnishing — destroying the original luster that gives a piece its mint-condition appeal.

Identifying PVC Damage

Look for these signs:

• A greenish or cloudy film on the metal surface that cannot be wiped away
• Sticky or tacky residue on the coin or on the inside of the holder
• A chemical odor when the holder is opened — PVC degradation has a distinctive acrid smell
• Discoloration patterns that match the contact points of the holder — for example, a circular mark from a coin capsule

The Trump/UFC Medallion Concern

This is directly relevant to the Trump/UFC Freedom 250 medallions being sold today. These items are being marketed as NGC-graded PF70 Ultra Cameo, meaning they are encapsulated in NGC’s sonically sealed acrylic holders, which are PVC-free. This is good. However, many buyers will remove these items from their certified holders for display, or they may purchase ungraded versions that come in PVC flips or soft plastic sleeves. If you are spending $12,000 on a gold medallion, the last thing you want is to store it in a $0.05 PVC flip that will damage the surface within a few years.

My strong recommendation: If you purchase one of these medallions, keep it in its NGC holder. If you must display it outside the holder, use only archival-quality, PVC-free acrylic or Mylar capsules. Never use soft plastic flips, and never store precious metal items in wooden boxes without proper archival lining. Your numismatic value depends on it.

Oxidation and Tarnish: The Silver Problem

While gold is essentially immune to oxidation, silver is not. Silver reacts with sulfur compounds in the atmosphere — hydrogen sulfide, sulfur dioxide, and even the trace amounts of sulfur found in some papers, fabrics, and rubber — to form silver sulfide (Ag₂S), which appears as a yellow, brown, or black tarnish film. For collectors of silver medallions, understanding this process is fundamental to preserving both luster and long-term value.

Factors That Accelerate Silver Oxidation

In my experience, the following environmental factors are the primary accelerants of silver tarnish:

1. High humidity: Relative humidity above 60% dramatically increases the rate of sulfide formation on silver surfaces
2. Air pollution: Urban environments with higher levels of sulfur dioxide and hydrogen sulfide cause faster tarnishing
3. Proximity to rubber: Rubber bands, rubber gaskets in display cases, and even some types of rubber gloves release sulfur compounds
4. Certain papers and fabrics: Newsprint, wool, and some dyed fabrics contain sulfur compounds that can tarnish silver on contact
5. Eggs and cooking vapors: This sounds absurd, but I’ve seen silver collections stored in kitchens develop heavy tarnish from cooking vapors containing hydrogen sulfide from egg proteins

Proper Silver Conservation

For the silver versions of the Trump/UFC medallions, proper conservation means:

• Storage in a dry, stable environment with relative humidity between 30-40%
• Use of anti-tarnish strips (such as Pacific Silvercloth or 3M anti-tarnish strips) in storage containers
• Never using commercial silver dips on numismatic items — these strip the surface layer along with the tarnish, destroying the original mint luster and potentially lowering the grade
• If cleaning is necessary, using only distilled water and a soft cotton cloth, or consulting a professional conservator

Proper Chemical Conservation: The Acetone Dip and Beyond

One of the most common questions I receive from collectors is about chemical cleaning. There is a widespread misconception that all chemical treatments are harmful to coins and medals. This is not accurate. The key is understanding which chemicals are safe and which are destructive — and that distinction can mean the difference between preserving a mint-condition patina and destroying it forever.

The Acetone Dip: Safe and Effective

Pure acetone (the solvent, not nail polish remover which contains additives) is the single safest chemical you can use on numismatic items. Acetone is an excellent organic solvent that will dissolve and remove:

• Adhesive residue from stickers and labels
• Oils and greases from handling
• Some types of organic contamination
• PVC residue (in early stages, before it has reacted with the metal surface)

Important: You must use 100% pure acetone, available from hardware stores or chemical suppliers. Drugstore “acetone” products often contain fragrances, oils, and other additives that can leave a residue on the metal surface.

The proper procedure for an acetone dip is:

1. Pour pure acetone into a clean glass container (not plastic — acetone dissolves many plastics)
2. Submerge the coin or medal for 30 seconds to a few minutes, depending on the severity of the contamination
3. Remove with tweezers (never bare hands — the acetone will strip the oils from your skin and transfer them back to the metal)
4. Rinse in a second container of clean acetone
5. Allow to air dry on a clean, lint-free surface — do not wipe or rub

I’ve used this technique hundreds of times in my conservation work, and when done properly, it causes absolutely no damage to the metal surface. It will not affect the grade of an NGC-certified coin if the item remains in its holder (and you should never dip a coin while it’s in a holder — the acetone can seep in and affect the label or the holder itself).

What NOT to Use

Equally important is knowing what to avoid. The following chemicals and treatments should never be used on numismatic items:

• Commercial silver dips: These contain thiourea or acid solutions that strip the surface layer of silver, destroying original luster and detail
• Vinegar or lemon juice: Acids that etch the metal surface and cause irreversible damage
• Baking soda paste: Abrasive — it will scratch the surface and destroy any mint luster
• Rubbing compounds or polishes: All polishes are abrasive to some degree and will remove metal from the surface
• Ultrasonic cleaners: The vibrations can cause micro-fractures in brittle alloys and can loosen details on high-relief items

Environmental Control: Building the Right Storage System

Prevention is always better than treatment. As a conservator, I’ve seen far more collections destroyed by improper storage than by any other single cause. Here is my recommended storage protocol for precious metal medallions and coins:

The Ideal Storage Environment

1. Temperature: Stable, between 65-72°F (18-22°C). Avoid attics, garages, and basements where temperature fluctuates dramatically.
2. Relative Humidity: 30-40% for silver, 35-45% for gold. Use a digital hygrometer to monitor conditions.
3. Air Quality: Avoid storage near kitchens, bathrooms, laundry rooms, or any area with chemical fumes. If you live in a high-pollution area, consider a sealed cabinet with activated charcoal filters.
4. Light: Store in the dark. UV light accelerates chemical reactions on metal surfaces and can cause discoloration of holders and labels.

Recommended Storage Materials

• NGC or PCGS certified holders: These are sonically sealed acrylic and are the gold standard (no pun intended) for long-term storage. Keep your certified items in their holders, period.
• Archival-quality Mylar flips: For uncertified items, use only Mylar (polyester) flips. Avoid PVC entirely.
• Acrylic capsules: Capital Plastics-style capsules are excellent for individual items.
• Archival boxes: Use acid-free, lignin-free boxes for bulk storage. Line with archival tissue if needed.

Materials to Avoid

• PVC flips, folders, or holders of any kind
• Wooden cabinets without archival lining
• Rubber bands or rubber-based adhesives
• Newsprint, regular cardboard, or colored paper
• Plastic bags (especially zip-lock types, which can trap moisture)

Case Study: What Could Happen to a $12,000 Medallion

Let me paint a picture that I’ve seen play out more times than I’d like to admit. A collector purchases the 1 oz Trump/UFC gold medallion for $11,999.99. It arrives in an NGC PF70 Ultra Cameo holder, and it’s stunning — deep mirror fields, frosty devices, perfect strike. The collector is thrilled.

But then, for one reason or another, the collector decides to remove the medallion from its holder for display in a custom frame. The frame uses a felt backing (which contains sulfur compounds) and is hung on a wall that gets direct sunlight. Over the next two years, the following happens:

1. The felt backing off-gasses sulfur compounds that begin to affect the gold surface (yes, even gold can develop surface contamination from sulfur, though it won’t corrode like silver)
2. The UV light causes the felt to degrade further, releasing more chemicals
3. Humidity fluctuations in the room cause condensation on the medallion’s surface during temperature changes
4. The collector handles the medallion with bare hands to show it to friends, leaving chloride-laden fingerprints on the surface

Two years later, the medallion has a hazy, dull appearance with visible fingerprint marks. The collector sends it back to NGC for regrading, and it comes back as an MS63 — a significant downgrade from PF70. The market value drops from $12,000 to perhaps $3,000-$4,000 (the gold bullion value plus a modest premium). A $12,000 asset has lost two-thirds of its value due entirely to improper storage and handling. The eye appeal that once made it a showpiece is gone.

This is not a hypothetical scenario. I’ve seen versions of this exact situation play out with gold American Eagles, Canadian Maple Leafs, South African Krugerrands, and countless commemorative issues. The metal doesn’t matter — the storage does. And once that original surface is compromised, no amount of conservation can fully restore the numismatic value.

Actionable Takeaways for Buyers and Sellers

Whether you’re considering purchasing one of the Trump/UFC Freedom 250 medallions or you already own precious metal collectibles, here are my top actionable recommendations:

1. Never remove certified items from their NGC or PCGS holders. The holder is not just for display — it’s a conservation device. It protects the surface from environmental damage, handling, and contamination.
2. Invest in a proper storage environment. A small dehumidifier and a digital hygrometer cost less than $50 and can protect a collection worth thousands.
3. Audit your current storage materials. Go through your collection right now and remove any items stored in PVC flips, wooden boxes, or near potential chemical sources. Replace with archival-quality materials.
4. Use pure acetone for surface cleaning — and only when necessary. If you see adhesive residue, organic contamination, or early-stage PVC damage, a brief acetone dip can save the surface. But don’t over-clean — every cleaning carries some risk.
5. Handle items only by the edges, and only with clean cotton or nitrile gloves. Never touch the obverse or reverse surfaces.
6. Document the condition of your items when you acquire them. Take high-resolution photographs in consistent lighting. This creates a baseline for detecting future environmental damage and is invaluable for insurance purposes and establishing provenance.
7. When in doubt, consult a professional conservator. The American Institute for Conservation (AIC) maintains a directory of qualified conservators. A single professional consultation can save you from making a costly mistake.

Conclusion: Protecting Your Investment in Precious Metal Numismatics

The Trump/UFC Freedom 250 medallions represent an interesting intersection of modern political memorabilia, sports marketing, and precious metal numismatics. Whether you view them as collectibles, investments, or conversation pieces, they are objects made of valuable metals that deserve proper care and conservation.

The numismatic market has evolved dramatically in recent decades. The rise of third-party grading services like NGC and PCGS has created a standardized system for evaluating condition, and the PF70 Ultra Cameo grade represents the pinnacle of that system. But a grade is only as good as the condition of the coin or medal it describes. Environmental damage doesn’t care about the grade on the holder — it will attack a PF70 just as readily as an uncirculated business strike. A rare variety in mint condition today can become a cautionary tale tomorrow if the storage environment isn’t right.

As a conservator, my message is simple: the most important thing you can do for your collection is not to buy the rarest or most expensive item — it’s to store and handle what you already have with the care it deserves. Bronze disease, PVC damage, oxidation, and improper chemical cleaning are all preventable. With the right knowledge, the right materials, and a little bit of discipline, you can ensure that your precious metal collectibles maintain their beauty, their historical significance, and their value for generations to come.

The medallions may be modern, but the principles of conservation are as old as the hobby itself. Treat your collection with the respect it deserves, and it will reward you in kind.

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