Emergency Money: The Wartime Context of Best Way to Remove Verdigris on 90% Silver Coins

Introduction: When Nations Turn to Emergency Coinage

During global conflict, mints had to adapt fast. I’ve examined countless wartime issues in my years as a numismatist, and few subjects ignite as much debate among collectors as the proper conservation of 90% silver coins. When I hold a piece from the emergency metal rationing era, I’m holding history that demands respect—and the right care to preserve its numismatic value.

The question of safely removing verdigris from 90% silver coins isn’t just a technical curiosity. It’s about preserving tangible links to eras when nations mobilized their economies for survival. The 90% silver alloy (90% silver, 10% copper), standard in U.S. coinage from 1795 through 1964, carries wartime metallurgy in its very makeup. Whether you’re looking to restore eye appeal or maintain mint condition, understanding this alloy is step one.

The Metallurgy of Wartime Silver Coinage

Understanding the 90/10 Alloy Under Siege Conditions

The 90/10 alloy wasn’t an accident; it was a deliberate choice. Copper gave the coin structural hardness, ensuring the soft silver could survive circulation without wearing down too fast. But that 10% copper is the root of much confusion regarding surface corrosion. In my grading work, I constantly see forum discussions about misidentifying these deposits. True verdigris is a copper compound—basic copper carbonate or acetate—formed through mineral reactions. It’s inorganic, which means acetone won’t touch it. This distinction is crucial for anyone handling wartime silver issues. Because the copper is locked into the alloy during the strike, verdigris rarely forms on the surface under normal conditions, unlike on pure copper or bronze.

Wartime Metal Shortages and Their Numismatic Legacy

The Chemistry of Survival: Why Wartime Coins Are Different

During WWII, the U.S. Mint faced impossible demands on its metal supplies. Silver went to photographic film and military applications; copper was needed for ammunition and wiring. The emergency response altered coin compositions entirely—the 1943 steel cent replaced copper, and silver coinage dropped to 80% before returning to 90% post-war. These shifts directly impact how we handle surviving examples today. I’ve often noted that coins struck under emergency conditions can have slightly different alloy distributions. The copper in the 90% silver blend might not have been as uniformly dispersed as in peacetime strikes. This unevenness, paired with the stresses of wartime storage, transport, and field circulation, created unique conservation challenges that affect a coin’s collectibility and long-term provenance.

Emergency Metal Rationing and Substitute Alloys

The wartime economy forced mints worldwide to experiment. In my grading experience, I’ve observed that coins from periods of metal rationing often show:

• Slightly different hardness profiles due to variations in copper distribution
• Greater susceptibility to surface corrosion from improper field storage
• Unique toning patterns from exposure to chemicals in military transport
• Evidence of PVC contact from original mint packaging or later albums

These factors make wartime 90% silver coins particularly vulnerable. What collectors often call “verdigris” is usually PVC-induced green deposits—or, in rare cases involving a specific rare variety stored in extreme conditions, true silver corrosion.

Verdigris vs. PVC: The Great Coin Confusion

The PVC Confusion on Silver Coins

Let’s clear up the biggest knowledge gap I see in the collecting community. When collectors spot green deposits on a 90% silver coin, they often panic and assume verdigris. But in most cases—especially with coins from 20th-century albums—the green stuff is PVC residue. It’s a plasticizer goo that migrates from vinyl holders, forming sticky, greenish deposits. PVC is organic, which is why acetone dissolves it effectively. I always recommend 100% pure acetone and a Q-tip; it removes the residue with minimal risk, evaporates completely, and the PVC won’t return.

True verdigris—copper carbonate—is a completely different beast. It forms when copper reacts with carbon dioxide and moisture over time. On pure copper or bronze, this is a persistent problem. On 90% silver coins, it rarely happens because the copper is locked in the alloy matrix. When it does appear—usually on coins subjected to extreme conditions, like shipwrecks or buried artifacts—it requires acidic solutions like sulfuric-acid-thiourea dips or ammonia-based cleaning to remove. Ignoring this can destroy the coin’s patina and ruin its mint condition.

Historical Survival Rates: Why Wartime Silver Coins Matter

The survival rate of wartime silver coins is a story of historical preservation in itself. Many circulated through military paychecks, wartime ration systems, and post-war reconstruction, stored in damp basements, field pouches, and military pay chests. These conditions accelerate PVC formation and, in rare cases, produce verdigris-like corrosion. When I acquire wartime silver issues, I know they carry a dual significance: emergency currency and human artifacts. The conservation approach must respect this dual nature. Proper care preserves not just the eye appeal but the numismatic value of these historical treasures.

Proper Conservation Techniques for Wartime Silver Issues

Step-by-Step: Safe Cleaning of 90% Silver Coins

Based on my grading experience and the collective wisdom from the forum, here’s how I systematically address green deposits on 90% silver coins:

1. Identify the deposit first. Is it PVC (organic, sticky, concentrated spots) or true corrosion (mineral-based, crystalline)? PVC comes off with acetone. True verdigris requires acid-based removal.
2. For PVC deposits: Use 100% pure acetone and a cotton swab. Apply gently. Acetone works fast—swirl the coin in a glass container, and results appear in minutes. The organic material dissolves completely and won’t return.
3. For true verdigris-like corrosion: Use a sulfuric-acid-thiourea dip or ammonia-based solution. These dissolve copper corrosion without excessive aggression. Always follow with a thorough rinse and proper storage to protect the strike and maintain mint condition.
4. Never use oil-based preservatives on silver. Silver is stable. Oil-based substances like VerdiCare are for copper and bronze. On silver, they trap dirt and kill the luster.
5. Store properly after cleaning. Use non-PVC flips, archival holders, or controlled storage to protect the coin’s collectibility and prevent future issues.

Risk Factors and Damage Prevention

When I examine wartime silver coins for grading, these are the most common conservation mistakes I see:

• Over-cleaning, which strips away the natural toning that adds value and eye appeal.
• Using abrasive materials (steel wool, harsh brushes) that permanently scratch the surface.
• Applying PVC-based coin holders to already-corroded coins, trapping moisture and accelerating damage.
• Confusing PVC deposits with verdigris, leading to inappropriate cleaning methods that ruin provenance.
• Leaving coins in acetone too long. Though acetone is safe, prolonged exposure risks surface abrasion from agitation.

The Wartime Context: Why Conservation Matters for Emergency IssuesRelated Resources

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