How to Properly Store and Preserve Elongated and Flattened Cents: A Conservationist’s Guide to Preventing PVC Damage, Oxidation, and Irreversible Harm

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

As a conservationist who has spent decades examining, cataloging, and preserving numismatic specimens — from ancient Roman denarii to modern elongated cents — I can tell you with absolute certainty that the single greatest threat to any coin collection is not time itself. It is the well-meaning but misguided actions of the collectors who own them. I have personally examined thousands of coins brought to me by hobbyists seeking appraisals, and heartbreakingly, a significant percentage of those pieces have suffered irreversible damage — not from age or natural wear, but from improper cleaning, destructive storage methods, and a fundamental misunderstanding of how toning, oxidation, and chemical reactions affect metal surfaces over time.

The recent forum discussion about members who collect flattened or elongated cents — those fascinating pieces of numismatic folk art created by rolling mills, railroad trains, and hand-cranked machines — reminded me that this niche area of collecting is particularly vulnerable to preservation mistakes. Elongated cents, by their very nature, have already undergone significant mechanical deformation. Their surfaces have been stretched, thinned, and altered from their original mint condition. This makes them both uniquely beautiful and uniquely fragile. Whether you collect Lincoln cents flattened by railroad tracks, elongated cents pressed at county fairs and tourist attractions, or the prized elongated Standing Liberty quarters once used as business cards by the legendary Mr. Cline, understanding proper conservation is essential to protecting your investment and preserving these pieces for future generations.

Understanding Toning: The Thin Line Between Beauty and Damage

One of the most misunderstood phenomena in all of numismatics is toning — the gradual color change that occurs on a coin’s surface as a result of chemical reactions between the metal and its environment. Toning is not inherently bad. In fact, some of the most valuable coins in existence are prized specifically for their spectacular, rainbow-hued toning patterns. But there is a critical distinction between attractive, stable toning and destructive, progressive toning, and understanding that difference is the first step in responsible coin conservation.

What Causes Toning on Copper and Bronze Coins

Elongated cents are predominantly struck on U.S. Lincoln cents, which means they are composed of copper (95%) with small amounts of zinc and tin (for coins minted after 1982, the composition shifts to 97.5% zinc with a thin copper plating). Copper is one of the most reactive metals used in coinage. When exposed to moisture, sulfur compounds, chlorine, or even the oils from human skin, copper begins to oxidize. This oxidation creates a thin layer of copper oxide on the surface, which initially appears as a warm, golden or reddish-brown patina. Over time, and with continued exposure to reactive compounds, this layer can darken to deep brown, chocolate, or even black.

The colorful “rainbow toning” that collectors admire is actually a phenomenon called thin-film interference. As the oxide layer grows to a specific thickness, it refracts light in ways that produce iridescent colors — blues, purples, magentas, and golds. This type of toning is generally stable and, when aesthetically pleasing, can significantly increase a coin’s numismatic value. However, if the chemical environment continues to change — if humidity fluctuates, if sulfur-rich compounds are introduced, or if the coin is stored in proximity to reactive materials — the toning can progress into destructive corrosion that eats into the metal itself.

How Toning Affects Elongated Cents Specifically

Elongated cents present a unique toning challenge because the stretching process during elongation thins the metal and can create micro-fractures in the surface. These tiny cracks become pathways for moisture and reactive chemicals to penetrate deeper into the metal than they would on a standard, unaltered cent. I’ve examined elongated cents where toning appeared superficial on the surface but had actually caused significant subsurface corrosion that weakened the structural integrity of the piece. This is why elongated cents demand even more careful environmental control than standard circulation-strike coins.

Oxidation: The Silent Destroyer of Copper Coinage

Oxidation is the chemical process by which metal atoms lose electrons to oxygen or other electronegative elements in their environment. On copper coins, oxidation manifests as a progressive darkening and eventual pitting of the surface. While a light, even patina on an elongated cent can be attractive and even desirable, unchecked oxidation is one of the most destructive forces your collection will face.

The Enemies of Copper: What to Watch For

In my experience grading and conserving copper numismatic items, I’ve identified the primary culprits behind destructive oxidation:

• Moisture and humidity: Relative humidity above 50% dramatically accelerates oxidation on copper surfaces. This is the single most important environmental factor to control.
• Sulfur compounds: Found in rubber bands, certain paper products, cardboard, wool, and even some adhesives. Sulfur reacts with copper to form copper sulfide, which appears as a dark, often irreversible black or greenish-black crust.
• Chlorides: Present in salt air, sweat, and some cleaning products. Chloride-induced corrosion on copper produces a distinctive green patina (verdigris) that can be deeply destructive.
• Acidic environments: Acidic paper, PVC-containing plastics, and even the acids naturally present in human skin can initiate and accelerate corrosive reactions.
• Proximity to other metals: When dissimilar metals are stored in direct contact, galvanic corrosion can occur, accelerating the deterioration of the more reactive metal (in this case, copper).

Preventing Oxidative Damage in Your Collection

The key to preventing oxidation is environmental control. I recommend the following practices for anyone collecting elongated or flattened cents:

1. Maintain stable humidity: Store your coins in an environment with relative humidity between 30% and 40%. Use silica gel packets or electronic dehumidifiers in your storage area.
2. Avoid handling with bare hands: Always wear clean, lint-free cotton or nitrile gloves when handling copper coins. The oils and salts on your skin can initiate corrosion within hours.
3. Never store coins in airtight containers without climate control: While it might seem logical to seal coins away from the air, an airtight container without humidity control can trap moisture and create a microenvironment that accelerates corrosion.
4. Keep coins away from direct sunlight and heat sources: Elevated temperatures accelerate all chemical reactions, including oxidation.

PVC Damage: The Hidden Threat Lurking in Your Coin Holders

If I could convey one piece of urgent advice to every coin collector in the world, it would be this: check every single coin holder in your collection for PVC content right now. PVC (polyvinyl chloride) damage is one of the most insidious and widespread threats to coin collections, and it is entirely preventable.

What Is PVC Damage and Why Is It So Destructive?

PVC was a common component in many soft, flexible coin holders, flips, and albums manufactured from the 1960s through the early 2000s. Over time, PVC breaks down and releases hydrochloric acid and chlorine gas. These chemicals react with the copper surface of a coin to form copper chloride, which appears as a distinctive greenish, sticky or powdery film. This green residue is not merely cosmetic — it represents active, ongoing corrosion that will continue to damage the coin’s surface until the chemical reaction is halted.

I have seen elongated cents — pieces that were beautifully detailed and sharply struck when they were first created — reduced to green-streaked, pitted shadows of themselves because they were stored in PVC flips for decades. The tragedy is that this damage is entirely irreversible. Once PVC corrosion has penetrated the surface of a coin, no conservation technique can restore the original detail. The coin’s grade, historical value, and market value are permanently diminished.

How to Identify PVC Holders

Not all soft, flexible coin flips contain PVC, but many do. Here is how to identify them:

• Smell test: PVC-containing flips often have a distinctive “plastic” or “new shower curtain” smell. If a coin holder has a noticeable chemical odor, it likely contains PVC.
• Visual inspection: PVC flips tend to become cloudy, sticky, or yellowish over time. If your flips are showing these signs of degradation, they are actively releasing harmful chemicals onto your coins.
• Age of the holder: Any soft plastic coin holder manufactured before 2000 should be treated as suspect unless you can confirm it is PVC-free.
• Flexibility and texture: PVC flips are typically very soft and stretchy. Modern PVC-free alternatives (made from Mylar, polyethylene, or polypropylene) tend to be slightly stiffer and have a more crinkly texture.

Immediate Action Steps

If you discover PVC holders in your collection, take the following steps immediately:

1. Remove all coins from PVC holders. Do this in a well-ventilated area, as the fumes from degrading PVC are not only harmful to coins but also to your health.
2. Inspect each coin for signs of PVC damage. Look for greenish spots, streaks, or a sticky residue on the surface.
3. Transfer coins to PVC-free holders immediately. Do not leave coins unprotected while you source new holders.
4. Document any damage. Photograph affected coins for your records and for any future insurance or appraisal purposes.

Proper Holders: Choosing the Right Storage for Elongated and Flattened Cents

Selecting appropriate storage for your elongated and flattened cents is not merely a matter of convenience — it is a critical conservation decision that will affect the long-term preservation of your collection. The right holder protects against physical damage, chemical contamination, and environmental fluctuations. The wrong holder can destroy a coin in a matter of years.

Recommended Holder Types

Based on my experience as a conservationist, I recommend the following holder types for elongated and flattened cents:

• Mylar (polyethylene terephthalate) flips: These are the gold standard for individual coin storage. Mylar is chemically inert, meaning it will not react with or off-gas onto your coins. It is also transparent, allowing for visual inspection without handling. Look for flips specifically labeled as “archival quality” and “PVC-free.”
• Cardboard 2×2 holders with Mylar windows: These are an excellent, cost-effective option for larger collections. The coin is placed between two pieces of cardboard, with a Mylar window that allows viewing. Ensure the cardboard is acid-free and lignin-free.
• Hard plastic capsules (Air-tite, Capital Plastics style): For higher-value elongated cents, hard plastic capsules provide superior physical protection. Choose capsules made from acrylic or polystyrene, and ensure they are PVC-free.
• Archival-quality coin albums: If you prefer album storage, select albums with pages made from acid-free, PVC-free materials. Avoid albums with soft, vinyl pages.
• Coin tubes (polyethylene or polypropylene): For bulk storage of lower-value elongated cents, archival-quality tubes are acceptable. Ensure they are made from polyethylene or polypropylene, never PVC.

Holder Materials to Avoid

Equally important as knowing what to use is knowing what to avoid:

• PVC flips and holders: As discussed above, these are actively destructive.
• Rubber bands: Rubber contains sulfur, which reacts with copper. Never use rubber bands to bundle coins or holders.
• Paper envelopes (non-archival): Standard paper contains acids and lignin that can cause spotting and discoloration on copper surfaces.
• Cardboard and wood boxes (non-archival): Untreated wood and standard cardboard off-gas acids and sulfur compounds.
• Adhesive mounts and stickers: The adhesives used in these products can chemically react with coin surfaces and leave permanent residues.

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

This is perhaps the most contentious topic in all of numismatics, and it is the question I am asked more frequently than any other: “Should I clean my coins?” My answer, as a conservationist, is almost always an emphatic no — but the full picture is more nuanced than that simple answer suggests.

Why Cleaning Is Almost Always a Mistake

When you clean a coin, you are removing material from its surface. Even the gentlest cleaning methods — soaking in distilled water, for example — remove some portion of the original metal and the natural patina that has developed over time. On an elongated cent, where the surface has already been mechanically altered and thinned, the margin for error is even smaller. Aggressive cleaning methods — using commercial coin cleaners, abrasive compounds, baking soda, vinegar, or any acidic or alkaline solution — can strip away surface detail, create unnatural brightness, and leave microscopic scratches that are visible under magnification.

The numismatic market heavily penalizes cleaned coins. A professionally graded elongated cent that has been cleaned will typically receive a detail grade (such as “Cleaned,” “Polished,” or “Damaged”) rather than a numerical grade, which can reduce its market value by 50% to 90% or more. I have personally examined coins that were worth hundreds or even thousands of dollars in their original, uncleaned state, reduced to a fraction of their value after a well-meaning owner attempted to “improve” their appearance.

The One Exception: Removing Active Corrosion

There is one circumstance in which I recommend intervention: when a coin is suffering from active, progressive corrosion — most commonly PVC damage or chloride-induced corrosion. In these cases, the corrosion will continue to destroy the coin if left unchecked, so carefully removing the corrosive material can halt further damage. However, this should be approached with extreme caution and, ideally, under the guidance of a professional conservator.

For PVC residue specifically, I recommend the following conservative approach:

1. Soak the coin in pure acetone (not nail polish remover, which contains additives). Acetone will dissolve PVC residue without reacting with copper. Use a glass container and work in a well-ventilated area.
2. Allow the coin to soak for several hours or overnight, replacing the acetone if it becomes cloudy or greenish.
3. Remove the coin and allow it to air-dry on a soft, lint-free cloth. Do not rub or wipe the surface.
4. Inspect the coin under magnification. If PVC residue remains, repeat the process.
5. Transfer the coin to a PVC-free holder immediately after treatment.

Important: Do not use acetone on coins with artificial toning, lacquer coatings, or other surface treatments, as it may strip these away. When in doubt, consult a professional conservator before attempting any cleaning procedure.

What About “Dipping” Coins?

“Dipping” refers to the practice of briefly immersing a coin in a mild acid solution (typically a commercial silver dip containing thiourea or a dilute acid) to remove surface tarnish and restore brightness. While this practice is more commonly associated with silver coins, some copper collectors have attempted it as well. I strongly advise against it. Dipping removes a thin layer of metal along with the tarnish, and the resulting “bright” appearance is artificial and short-lived. The coin will typically re-tarnish quickly, often unevenly, and the process can be repeated only a limited number of times before significant metal loss occurs. Professional grading services can easily detect dipped coins, and the practice will negatively affect both grade and value.

Building a Preservation-First Mindset for Your Elongated Cent Collection

Whether you are a member of TEC (The Elongated Collectors), a casual hobbyist who picked up a few pressed pennies on your last vacation, or a serious collector with a fair-sized collection of elongated cents and Standing Liberty quarters, adopting a preservation-first mindset is the single most important thing you can do for your collection. The principles I’ve outlined here — understanding toning, preventing oxidation, eliminating PVC from your storage, choosing proper holders, and resisting the urge to clean — are not complicated, but they require discipline and consistency.

Actionable Takeaways for Every Collector

To summarize, here are the essential preservation practices I recommend for every collector of elongated and flattened cents:

1. Audit your storage materials today. Remove all coins from PVC flips, rubber bands, and non-archival holders. Replace them with Mylar flips, archival cardboard 2x2s, or hard plastic capsules.
2. Control your storage environment. Maintain relative humidity between 30% and 40%. Avoid temperature fluctuations, direct sunlight, and proximity to chemicals or reactive materials.
3. Handle coins with gloves. Never touch the surface of a copper coin with bare hands.
4. Never clean your coins. Accept the natural patina and toning as part of the coin’s character and history. The only exception is the careful removal of active PVC corrosion using pure acetone.
5. Document your collection. Photograph each coin and note its condition, provenance, and any relevant details. This documentation is invaluable for insurance, estate planning, and future sales.
6. Educate yourself continuously. Join organizations like TEC (The Elongated Collectors) at tecnews.org to stay informed about best practices, new research, and conservation techniques.
7. Consult professionals when in doubt. If you are unsure about the condition of a coin, the appropriateness of a storage method, or the best course of action for a damaged piece, seek the advice of a professional conservator or a reputable grading service.

Conclusion: Preserving Numismatic Heritage for Future Generations

Elongated and flattened cents occupy a unique and cherished place in the world of numismatics. They are not merely coins — they are artifacts of American culture, souvenirs of travel and tourism, and tangible connections to the mechanical ingenuity of the elongated coin machines that created them. The elongated Standing Liberty quarters used as business cards by Mr. Cline, the railroad-flattened copper cents that bear the marks of industrial America, and the countless elongated cents pressed at fairs, zoos, and landmarks across the country all represent a rich and fascinating chapter of numismatic history.

As collectors, we are not the permanent owners of these pieces. We are their temporary stewards — caretakers entrusted with the responsibility of preserving them for the next generation of collectors, historians, and enthusiasts. Every decision we make about storage, handling, and conservation either fulfills or betrays that trust. I have seen too many valuable pieces ruined by improper cleaning or storage, and I have seen too many collectors learn this lesson the hard way, after the damage is already done.

The good news is that proper preservation is not expensive or complicated. PVC-free holders are readily available and affordable. Environmental control requires only basic awareness and a few simple tools. And the discipline to resist cleaning your coins requires nothing more than patience and respect for the natural aging process. By following the principles outlined in this guide, you can ensure that your elongated and flattened cent collection remains in excellent condition — a source of pride, enjoyment, and historical value for decades and generations to come.

Preserve wisely. Handle gently. Store properly. And never, ever clean your coins.

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