Verdigris and PVC: Saving Israeli Coins — Underappreciated Gems of Historical Coins from Environmental Damage

Improper storage is the silent enemy of every coin collection I’ve ever worked with. In this guide, I’m going to walk you through how to spot and address the specific forms of environmental damage that threaten Israeli coinage.

As someone who has spent decades examining, grading, and preserving coins from every corner of the globe, I can tell you that few areas of collecting present as many preservation challenges — or as many underappreciated opportunities — as Israeli coinage. From the earliest Prutah and Agorot denominations of 1949 through the modern Shekel and commemorative series, these coins are historically rich, artistically distinctive, and unfortunately highly susceptible to environmental degradation. Whether you are a seasoned collector assembling a date set, an investor eyeing Biblical Art series silver, or a historian drawn to the continuity between ancient Judaean bronzes and their modern successors, understanding how to identify and mitigate environmental damage is essential to protecting your holdings.

Here, I’ll cover the specific threats facing Israeli coins — particularly those struck in bronze, copper-nickel, and aluminum — and share conservation techniques you can put to use immediately. We’ll tackle bronze disease, PVC plasticizer damage, oxidation patterns, and proper chemical treatments including acetone dips. Along the way, I’ll reference specific Israeli series and denominations to keep everything grounded in real-world collecting.

Why Israeli Coins Deserve Your Attention — and Your Care

Before we get into the science of conservation, it helps to understand why Israeli coins occupy such a unique — and often overlooked — niche in world numismatics. These coins face three significant barriers to widespread collecting: political sensitivities, the Hebrew language barrier, and a distinctive art style rooted in the Jewish prohibition against graven images. The result is a series that is deeply meaningful to those who collect it but remains undervalued relative to its historical significance.

The designs of Israel’s earliest coins deliberately echoed ancient Judaean issues. The bunch of grapes on the 25 Prutot coin, for example, was derived from bronzes of the Bar Kochba revolt (132–133 AD). The grape leaf on the 50 Prutot traced its lineage to the bronze Prutah of the First Jewish Revolt (66–70 AD). This continuity spanning nearly two millennia makes Israeli coins a living bridge between ancient and modern history — and makes their preservation all the more important.

The series encompasses a wide range of metals and compositions:

• Aluminum — early denominations like the 1948 25 Mils (War of Independence issue, approximately 40,000 issued)
• Bronze and copper alloys — Prutah and early Agorot denominations
• Copper-nickel — later circulating issues including the Half Shekel
• Silver — commemorative issues, Biblical Art series, Wildlife series, and the Akko UNESCO two-coin set
• Gold — limited commemorative and bullion issues
• Piefort (double-thick) strikes — special collector editions

Each of these metals responds differently to environmental threats, and a one-size-fits-all approach to storage and conservation will inevitably lead to damage. So let’s examine the specific dangers one by one.

Bronze Disease: The Silent Killer of Israeli Copper Alloy Coins

What Is Bronze Disease?

Bronze disease is the single most destructive environmental threat facing copper-alloy coins, and it is particularly relevant to collectors of early Israeli bronzes. It is a form of corrosion caused by the interaction of copper chloride compounds within the alloy with moisture and oxygen. The result is a characteristic bright green, powdery or fuzzy crystalline growth — often confused with ordinary verdigris but fundamentally different in both appearance and danger.

I have examined numerous Israeli Prutah and Agorot pieces that arrived at my workbench already in advanced stages of bronze disease. The early bronze issues, minted in the late 1940s and 1950s, are especially vulnerable because their copper-rich compositions and decades of exposure to humid Mediterranean climates create ideal conditions for chloride activation.

How to Identify Bronze Disease

In my experience grading and conserving Israeli coins, I look for these telltale markers:

• Bright, lime-green crystalline spots that protrude from the surface — not the flat, dark green patina of stable oxidation
• A powdery or fuzzy texture when viewed under magnification (a 10x loupe is essential)
• Active spreading — if the green spots appear to be growing between examinations, the disease is active
• Pitting beneath the crystals — when the green powder is removed, irregular pitting is visible in the metal, indicating ongoing material loss
• A sharp, acrid smell when the coin is placed near moisture — the hydrochloric acid produced by the reaction is detectable

Here is something many collectors overlook: bronze disease is contagious. An actively diseased coin stored in proximity to healthy copper-alloy coins can spread chloride contamination through airborne moisture. This is especially dangerous for those assembling complete date sets in albums or trays where multiple bronze issues sit side by side.

Treating Bronze Disease in Israeli Coins

The conservation protocol I recommend for bronze disease in Israeli coins involves several steps:

1. Isolate the affected coin immediately from all other copper-alloy pieces.
2. Mechanical cleaning under magnification — using a fine wooden probe (bamboo skewer) or a soft-bristled brush, carefully remove the bulk of the green crystalline growth. Work under a magnifying lamp and avoid scratching the original surface.
3. Sodium sesquicarbonate soak — prepare a solution of sodium sesquicarbonate (available from conservation supply houses) and soak the coin for 24–48 hours. This neutralizes the copper chloride compounds. For particularly stubborn cases, I have extended soaks to one week, changing the solution every 48 hours.
4. Thorough rinsing — rinse the coin in multiple changes of distilled water (never tap water, which contains chlorides that can reactivate the disease).
5. Final drying — allow the coin to air-dry completely in a low-humidity environment before applying any sealant.
6. Protective coating — apply a thin layer of Incralac (an acrylic lacquer with benzotriazole corrosion inhibitor) or a quality microcrystalline wax such as Renaissance Wax.

Important note: Do not attempt to treat bronze disease with commercial cleaning products, vinegar, or lemon juice. These acidic treatments will accelerate corrosion and destroy the coin’s surface detail and any remaining original patina — permanently reducing both its numismatic value and eye appeal.

PVC Plasticizer Damage: The Hidden Threat in Coin Holders

The Problem with PVC Flips and Albums

One of the most common forms of environmental damage I encounter in Israeli coins — particularly in collections purchased from estates or older dealers — is PVC (polyvinyl chloride) plasticizer damage. Many collectors, especially those who acquired Israeli coins in the 1960s through 1980s when awareness of proper storage was limited, stored their pieces in PVC-containing plastic flips, soft vinyl albums, or adhesive coin holders.

PVC is inherently unstable. Over time, it releases plasticizers (primarily phthalates) and hydrochloric acid gas. These chemicals react with the metal surface of coins, producing a characteristic greenish, sticky or tacky film that can range from light surface haze to deep, irreversible corrosion.

This is a significant conservation concern for Israeli coinage specifically. The Israel Coins and Medals Corporation, in its early decades, was not always attentive to archival-quality packaging. Many commemorative and proof issues were shipped in PVC-laden presentation cases or soft vinyl flips — meaning that even coins in original packaging may be actively deteriorating.

Identifying PVC Damage

I look for these signs when examining Israeli coins for PVC damage:

• A greenish or bluish-green film or residue on the coin’s surface, often with a slightly sticky or greasy feel
• Haze or cloudiness on proof or specimen surfaces — particularly devastating on Israeli proof sets and piedfort strikes where mirror fields and original luster are key grading elements
• Damage pattern matching storage contact points — if a coin was stored in a known PVC holder, the damage often mirrors where the holder touched the coin
• Odor — PVC-damaged coins sometimes retain a faint chemical smell, especially when first removed from storage

Removing PVC Residue: The Acetone Dip Method

Fortunately, PVC residue can often be removed if caught before deep corrosion has set in. The standard conservation treatment I employ is an acetone bath:

1. Use pure, reagent-grade acetone — available from chemical supply houses or hardware stores. Do not use nail polish remover, which contains oils, fragrances, and moisturizers that will leave their own residue on the coin.
2. Submerge the coin in a glass container of acetone. I use a glass jar with a tight-fitting lid. Do not use plastic containers, as acetone will dissolve many plastics.
3. Soak for 5–15 minutes — for light surface haze, a brief soak is sufficient. For heavier deposits, I extend the soak and use a soft cotton swab gently dabbed on the affected areas while the coin is submerged.
4. Remove and allow to air-dry — acetone evaporates rapidly. Do not rinse with water. Allow the coin to dry completely in open air.
5. Inspect under magnification — if residue remains, repeat the process. Stubborn PVC residue may require multiple acetone baths.
6. Apply protective coating — once the PVC residue is fully removed and the coin is dry, apply Renaissance Wax or Incralac to prevent future chemical interaction.

Critical safety note: Acetone is highly flammable and produces strong vapors. Work in a well-ventilated area, wear nitrile gloves, and keep away from open flames. Acetone will not damage the metal of copper, bronze, silver, or gold coins, but it will damage any organic coatings, lacquers, or adhesives on a coin. It can also affect certain modern commemorative finishes — when in doubt, test an inconspicuous area first or consult a professional conservator.

Prevention: Proper Storage Materials

The best treatment for PVC damage is prevention. I recommend the following storage materials for Israeli coins:

• Mylar (polyethylene terephthalate) flips — archival safe, chemically inert
• Polyethylene flips — also safe and widely available
• Acrylic capsules — such as those produced by PCGS, NGC, or Capitol plastic holders
• Acid-free tissue paper — for wrapping individual coins
• Archival-quality albums — specifically labeled “PVC-free” from reputable suppliers like Lighthouse, Lindner, or Dansco

Never store Israeli coins — or any coins — in: soft PVC flips, rubber bands, paper envelopes with adhesive flaps, cardboard holders with PVC windows, or wooden cabinets with unsealed surfaces (wood off-gasses acids that accelerate corrosion).

Oxidation and Toning: Understanding the Spectrum from Beautiful to Destructive

The Role of Environment in Oxidation

Oxidation is the most universal form of environmental damage affecting coins, and Israeli coins are no exception. The rate and character of oxidation depend on several environmental factors:

• Humidity — relative humidity above 50% dramatically accelerates oxidation of copper, bronze, and silver. Israel’s Mediterranean climate, with its coastal humidity, means that coins stored in-country without climate control are at elevated risk.
• Airborne pollutants — sulfur compounds (from industrial emissions, rubber, wool), chlorides (from sea air, handling with bare hands), and nitrogen oxides all contribute to tarnish and corrosion.
• Temperature fluctuations — cycling between warm and cool environments causes condensation on coin surfaces, accelerating oxidation.
• Direct contact with other materials — coins stored in contact with paper, cardboard, leather, or certain plastics will develop localized toning or staining corresponding to the contact points.

Natural Toning vs. Damaging Oxidation

There is an important distinction in numismatics between attractive, stable toning and destructive oxidation. On Israeli silver commemoratives — particularly the Biblical Art series, Wildlife series, and city commemoratives like the Akko UNESCO two-silver-coin set — natural toning can develop into spectacular rainbow or golden hues that enhance both beauty and market value. I have seen superbly toned Israeli proof silver coins that display breathtaking iridescent patina across their fields, and these pieces command significant premiums precisely because of their eye appeal.

However, destructive oxidation presents quite differently:

• Dark, uneven brown or black toning that obscures design details
• Pitting visible under magnification — indicating that the oxidation has progressed beyond surface discoloration into actual metal loss
• Chalky or crusty surface texture — particularly on aluminum issues like the early 1948 25 Mils
• Bronze or copper deposits on silver coins — indicating alloy migration in clad or bimetallic compositions (relevant to some modern Israeli commemoratives)

Aluminum-Specific Concerns

Israeli aluminum coins, particularly the early denominations, present a unique conservation challenge. Aluminum forms a thin, protective oxide layer (Al₂O₃) almost instantly upon exposure to air. This layer is generally stable and protective. However, in the presence of chlorides (from salt air or handling) or strong acids/bases, aluminum can develop localized pitting corrosion that appears as white, powdery spots or shallow pits.

The 1948 25 Mils aluminum issue (War of Independence) — with its mintage of approximately 40,000 pieces — is a prime candidate for aluminum corrosion. Specimens in true mint condition are already challenging to find, and those with clean, unblemished surfaces are even rarer. This is a rare variety where condition directly drives collectibility. I strongly recommend storing aluminum Israeli coins in low-humidity environments (below 40% relative humidity) and avoiding any contact with chloride-containing materials.

Chemical Conservation: A Practical Guide for Israeli Coin Collectors

When to Use Acetone — and When Not To

As discussed in the PVC section above, acetone dips are a valuable conservation tool. However, it is important to understand their proper application and limitations. In my conservation practice, I use acetone for the following purposes on Israeli coins:

• Removing PVC residue and plasticizer contamination
• Removing adhesive residue from labels, tape, or stickers applied by previous owners
• Removing organic contaminants such as oils, greases, and fingerprints (though for fingerprints, I prefer a gentler approach — see below)
• Preparing surfaces for protective coating application

I do not use acetone for:

• Removing toning or patina — acetone is a solvent, not a metal cleaner. It will not remove oxidation or tarnish from the metal itself.
• Cleaning active bronze disease — acetone will not neutralize copper chloride compounds and may spread contamination.
• Treating coins with applied color or enamel — some modern Israeli commemoratives feature colored elements that acetone will destroy.
• Cleaning proof or specimen surfaces — acetone can alter the reflective properties of proof fields, potentially reducing the coin’s grade and destroying the original luster that gives mint-condition pieces their premium.

Gentle Cleaning for Fingerprints and Light Contamination

For Israeli coins with light surface contamination — fingerprints, dust, or minor haze — I recommend a gentler approach than acetone:

1. Warm distilled water and mild soap — a drop of pure castile soap in distilled water, applied with a soft cotton swab. Rinse thoroughly in distilled water and pat dry with a lint-free cloth.
2. Distilled water soak — for coins with water-soluble contaminants, a soak in distilled water (changed several times) can be effective without any chemical intervention.
3. Mechanical removal — for isolated spots of contamination, a wooden probe or soft vinyl eraser used gently under magnification can remove surface debris without chemicals.

What Never to Do: Harmful Cleaning Methods to Avoid

Over my career, I have seen irreparable damage caused by well-intentioned but misguided cleaning attempts. Never use the following on Israeli coins (or any numismatic items):

• Commercial metal polishes (Brasso, Silvo, etc.) — these contain abrasives that will scratch the surface and remove original mint luster
• Vinegar, lemon juice, or other acids — these will strip patina and accelerate future corrosion
• Baking soda or other alkaline cleaners — abrasive and chemically reactive with many coinage metals
• Electrolytic cleaning — while used in some archaeological conservation contexts, electrolytic cleaning is inappropriate for numismatic coins as it removes original surface material
• Rubbing with abrasive materials — steel wool, scrubbing pads, or rough cloths will permanently damage the coin’s surface

A conservator’s cardinal rule: The goal of numismatic conservation is to stabilize and preserve, not to restore or improve. Any treatment that removes original metal, alters the surface texture, or changes the natural patina of a coin is, in my professional opinion, inappropriate for collectible numismatic material.

Environmental Control: Building the Proper Storage Environment

Humidity and Temperature

The single most important factor in preventing environmental damage to your Israeli coin collection is controlling the storage environment. I recommend the following parameters:

• Relative humidity: 30–40% — below the 50% threshold where oxidation accelerates, but above the 20% threshold where some materials become brittle
• Temperature: 65–70°F (18–21°C) — stable, with minimal fluctuation
• No direct sunlight — UV radiation accelerates PVC degradation and can alter toning patterns
• Minimal air circulation with clean air — avoid storage near kitchens (cooking fumes), bathrooms (humidity), garages (automotive chemicals), or industrial areas

Desiccants and Monitoring

For collectors in humid climates — or for valuable Israeli pieces that warrant extra protection — I recommend using silica gel desiccant packets in storage containers. Rechargeable silica gel (the type that changes color when saturated) allows you to monitor humidity levels visually. Place a small humidity indicator card inside each storage cabinet or safe for continuous monitoring.

Handling Protocols

Even with perfect storage conditions, improper handling can introduce contaminants that initiate environmental damage. I follow these protocols and recommend them to all collectors:

• Always handle coins by the edges — never touch the obverse or reverse surfaces
• Wear clean cotton or nitrile gloves when handling valuable pieces
• Handle coins over a soft surface — a velvet pad or clean towel — to minimize damage from drops
• Never clean a coin before showing it to a buyer or grader — natural toning and surface condition are key grading factors that affect numismatic value
• Wash and dry hands thoroughly before handling if gloves are not available

Series-Specific Conservation Notes for Israeli Collectors

Biblical Art Series (Silver)

The Biblical Art series — including popular designs such as Elisha and the Chariot and the Splitting of the Red Sea — is among the most collectible and valuable of Israeli commemorative issues. These silver coins are particularly prized for their artistic merit and historical resonance. They are also particularly susceptible to PVC damage (many were originally sold in PVC-laden presentation cases) and to uneven toning if stored in non-archival materials.

I recommend individual archival capsules for each Biblical Art coin, stored in a controlled environment. If you acquire one of these pieces in original packaging, inspect the packaging carefully for PVC content and transfer the coin to archival storage if necessary. The provenance of original packaging has value, but not at the cost of the coin itself.

Wildlife and Birds of the Holyland Series

The Wildlife series and the Birds of the Holyland series have proven to have lasting collector interest. These silver commemoratives often feature high-relief designs with fine detail that can trap contaminants in recesses. Pay particular attention to the areas around bird feathers, animal fur, and botanical elements when inspecting for early signs of corrosion or contamination. A strong loupe is your best friend here.

City Commemoratives (Akko, Hebron, etc.)

City commemoratives, including the stunning Akko UNESCO two-coin silver set and the coin commemorating the ancient Jewish community in Hebron, are among the most artistically accomplished issues in the Israeli series. Their large diameters and detailed designs make them both visually impressive and conservation-challenging. Store these in appropriately sized archival capsules that do not put pressure on the rims, and inspect regularly for edge toning or rim discoloration that may indicate environmental exposure.

Early Bronze and Copper-Nickel Circulating Issues

The early Prutah and Agorot denominations — the workhorses of Israel’s early monetary system — are the coins most likely to exhibit bronze disease and heavy oxidation. Many of these circulated extensively in Israel’s humid coastal cities before being collected. When assembling a date set of these issues, inspect each piece carefully under magnification for active bronze disease before placing it in an album with other copper-alloy coins. One diseased coin can compromise an entire set.

Aluminum Issues (1948–1960s)

Early aluminum coins, including the key 1948 25 Mils War of Independence issue, are soft and easily scratched. They are also susceptible to chloride-induced pitting. Store these in individual hard capsules rather than album pages, which can abrade the soft aluminum surfaces through repeated insertion and removal. Preserving the original strike detail on these early issues is critical to maintaining their collectibility.

Error Coins and Special Strikes: Conservation Considerations

Error coins and special strikes deserve particular conservation attention because their numismatic premium depends entirely on their condition and authenticity. A possible 25 Agorot piece struck on a 10 Agorot planchet — a wrong-planchet error that, if confirmed by weighing (6.5 grams expected vs. 5 grams for the smaller planchet), would be a significant find — must be preserved exactly as found. The same applies to piefort sets and other special collector editions.

I recommend the following for error coins and special strikes:

• Never attempt to “improve” the appearance of an error coin — any cleaning or alteration will destroy the premium
• Document the error with high-resolution photographs before and after any conservation treatment
• Store in hard, inert capsules that protect the coin’s surfaces while allowing visual inspection
• Consider professional grading and encapsulation (PCGS, NGC) for significant errors, as this provides both authentication and permanent archival storage

Actionable Takeaways for Buyers and Sellers

Whether you are buying Israeli coins at auction, through private treaty, or from online marketplaces, use this checklist to assess environmental damage before completing your purchase:

1. Request high-resolution photographs of both sides, the edge, and any problem areas. Ask for images taken under magnification if the coin shows any signs of surface issues.
2. Ask about storage history — was the coin stored in PVC flips, wooden cabinets, or archival materials? Has it been previously cleaned? Provenance matters.
3. Inspect for bronze disease — look for bright green, powdery spots on copper-alloy coins. If present, factor treatment costs into your purchase price.
4. Check for PVC damage — look for greenish sticky film, haze on proof surfaces, or chemical odor.
5. Assess toning honestly — distinguish between attractive natural toning (a value enhancer that adds eye appeal) and destructive oxidation (a value detractor).
6. Weigh the coin — compare against standard references. Weight discrepancies may indicate corrosion metal loss, planchet errors, or authenticity issues.
7. Transfer to archival storage immediately upon acquisition — do not allow a newly purchased coin to remain in non-archival dealer packaging.

For sellers, the inverse applies:

1. Store coins in archival materials before listing — a coin presented in a PVC flip signals carelessness to knowledgeable buyers and undermines confidence in your other offerings.
2. Disclose any known damage or previous conservation treatments — transparency builds trust and protects you legally.
3. Photograph under neutral lighting — avoid filters or editing that alter the apparent color or surface condition.
4. Consider professional grading for high-value pieces — a PCGS or NGC encapsulation provides an independent assessment of condition and authenticity that facilitates sales and maximizes numismatic value.

Conclusion: Preserving the Legacy of Israeli Numismatics

Israeli coins represent one of the most historically compelling series in all of world numismatics. From the rebirth of Jewish sovereignty in 1948 — celebrated in the very metal of the nation’s first coins — through the deliberate echoes of Bar Kochba and First Revolt designs, to the artistic achievements of the Biblical Art and Wildlife series, these coins carry a weight of meaning that transcends their metal content.

Yet Israeli coins remain underappreciated. The language barrier, political sensitivities, and the sheer volume of NCLT commemoratives have kept many collectors from exploring this rich series. For those of us who do collect Israeli coins, the responsibility of stewardship is paramount. These are not merely metal discs — they are artifacts of a nation’s founding, its struggles, its faith, and its artistic vision.

Environmental damage — whether from bronze disease, PVC contamination, oxidation, or improper handling — threatens to erase the detail, beauty, and historical integrity of these coins. But with proper knowledge, appropriate conservation techniques, and archival-quality storage, we can ensure that Israeli coins survive in the best possible condition for future generations of collectors, historians, and admirers.

As I tell every collector who brings me a damaged coin: the best time to start proper conservation was when you acquired the piece; the second-best time is now. Inspect your Israeli holdings today. Identify the threats. Implement the solutions. And enjoy the profound satisfaction of preserving a tangible link to one of history’s most remarkable stories.

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