Preserving Your Twenty Cent Piece: Expert Conservation Techniques

The Conservationist’s Warning: Why Proper Preservation Matters

I’ve seen too many valuable pieces ruined by improper cleaning or storage. Here’s how to keep this safe for the next generation.

Twenty cent pieces, minted from 1875 to 1878, represent a fascinating but short-lived chapter in American coinage. These coins were quickly withdrawn from circulation due to confusion with quarters, making them particularly desirable to collectors today. However, their silver composition makes them vulnerable to various forms of damage that can permanently diminish their numismatic value.

Understanding Toning and Oxidation

Toning is a natural process that occurs when silver coins are exposed to sulfur compounds in the air, developing a range of colors from golden hues to deep blues and purples. While some collectors prize attractive toning, others prefer original mint luster. The key is that toning should develop naturally over decades rather than being artificially induced.

Oxidation, on the other hand, can be destructive. When silver coins are exposed to excessive humidity or pollutants, they can develop black spots or tarnish that eats into the surface. This is particularly problematic for twenty cent pieces, as their large surface area makes them more susceptible to environmental damage.

Best practices for toning/oxidation:

• Store coins in a cool, dry environment with stable temperature and humidity
• Use silica gel packets in storage containers to absorb excess moisture
• Avoid storing coins in basements, attics, or areas prone to temperature fluctuations
• Never clean coins with commercial cleaners or abrasive materials

The PVC Threat: Recognizing and Preventing Damage

Polyvinyl chloride (PVC) is one of the most destructive substances for coin preservation. Many older coin holders and flips contained PVC, which can leach out over time and create a greenish, slimy residue that permanently damages the coin’s surface.

Looking at the twenty cent piece in question, we can see evidence of what might have been PVC damage or other chemical reactions that created raised lines across the surface. These raised areas are actually displaced metal, similar to how a plow blade creates ridges in soil.

Signs of PVC damage include:

• Greenish or yellowish deposits on the coin surface
• Sticky or slimy texture
• Raised areas where the plastic has chemically reacted with the metal
• Pitting or etching on the surface

Prevention is simple:

• Always use PVC-free holders and flips
• Store coins in archival-quality materials
• Replace old holders that may contain PVC
• Never store coins in vinyl pages or soft plastic containers

Proper Holders: The First Line of Defense

The holder you choose can make the difference between a coin that survives for generations and one that deteriorates rapidly. For twenty cent pieces, which are relatively large and valuable, proper storage is especially critical.

Recommended holder types:

• Archival-quality flips made from polyester or Mylar
• Airtight holders for particularly valuable specimens
• Acid-free cardboard 2×2 holders with Mylar windows
• Proper coin albums with archival pages

Avoid any holders that feel soft or flexible, as these often contain PVC. The holder should feel rigid and have no chemical odor.

To Clean or Not to Clean: The Conservationist’s Perspective

This is perhaps the most controversial topic in coin collecting. As a conservationist, my position is clear: never clean collectible coins. Cleaning, even when done carefully, removes the natural patina and microscopic details that give coins their character and value.

The twenty cent piece we’re examining shows what happens when coins are improperly cleaned or damaged. The raised lines across the surface are actually displaced metal from what appears to be a cut or scratch. This damage, combined with subsequent circulation wear, creates the appearance of something more mysterious than it actually is.

Why cleaning is destructive:

• Removes natural toning and patina
• Creates microscopic scratches that reduce detail
• Can remove metal from the surface, reducing weight
• Often makes coins appear unnaturally bright and unattractive to collectors
• Significantly reduces collector value

If you absolutely must address environmental damage, consult a professional conservationist who specializes in numismatics. They have specialized techniques and materials that can stabilize coins without causing additional harm.

Case Study: The Damaged Twenty Cent Piece

The twenty cent piece that sparked this discussion provides an excellent teaching opportunity. What appears at first glance to be something mysterious is actually straightforward damage that occurred after the coin left the mint.

The raised lines across the surface are classic examples of displaced metal. When a sharp blade cuts into silver at an angle, it pushes metal to one side, creating raised ridges. This is similar to how a plow creates ridges of soil alongside a furrow.

Several factors confirm this is post-mint damage (PMD):

• The lines are inconsistent with any known mint error
• PCGS, the professional grading service, identified it as PMD
• The damage shows signs of wear, indicating it occurred long ago and the coin circulated afterward
• The pattern is consistent with intentional damage rather than a minting anomaly

This case illustrates why proper storage is so important. Had this coin been stored correctly from the beginning, it would have retained its original condition and potentially much higher value.

Creating the Ideal Storage Environment

Beyond choosing the right holders, you need to consider the overall storage environment. Coins are sensitive to their surroundings, and even the best holders can’t protect against extreme conditions.

Optimal storage conditions:

• Temperature: 65-70°F (18-21°C)
• Relative humidity: 45-55%
• Minimal light exposure, especially direct sunlight
• Stable conditions without rapid fluctuations
• Protection from air pollutants and sulfur compounds

Consider using a dedicated coin cabinet or safe that provides both physical security and environmental control. Many collectors use small dehumidifiers or silica gel in their storage areas.

Long-term Preservation Strategies

Preserving coins for future generations requires ongoing attention and periodic review of your storage methods.

Regular maintenance includes:

• Periodically checking holders for signs of deterioration
• Replacing old holders before they damage coins
• Monitoring storage area conditions with a thermometer/hygrometer
• Handling coins only with clean, dry hands or cotton gloves
• Keeping coins in a secure location away from potential accidents

Document your collection with photographs and descriptions. This not only helps with insurance but also creates a record for future collectors in your family.

The Value of Preservation

While the damaged twenty cent piece in our example has significantly reduced value, a well-preserved specimen of the same date and mint mark could be worth hundreds or even thousands of dollars depending on condition.

Conservation isn’t just about maintaining value—it’s about preserving history. Each coin tells a story about the era when it was minted, the people who used it, and the economic conditions of the time. When we preserve coins properly, we preserve these connections to our past.

Conclusion: Your Role as a Conservationist

Whether you’re a seasoned collector or just starting out, you have a responsibility to preserve numismatic history. The twenty cent piece, with its brief production run and historical significance, deserves careful preservation.

Remember these key principles:

• Never clean collectible coins
• Use only archival-quality storage materials
• Control temperature and humidity
• Handle coins minimally and carefully
• Document and monitor your collection

By following these guidelines, you’ll ensure that your twenty cent pieces and other numismatic treasures survive in excellent condition for future collectors to study and appreciate. The next generation of numismatists will thank you for your conservation efforts.

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