Preserving Shipwreck Treasures: Expert Conservation Techniques for Coins and Artifacts

I’ve Held History in My Hands: A Conservator’s Plea to Save Our Sunken Treasures

After thirty years preserving shipwreck artifacts, I’ve witnessed gut-wrenching losses that keep me awake at night. Picture this: Mexican pillar dollars from the Reigersdaal wreck, their once-vibrant surfaces reduced to crumbling green corrosion. Or the heartbreaking case of an 1877-S gold sovereign from the RMS Douro, its legendary strike obscured by PVC-induced crusting. These aren’t mere collectibles – they’re time capsules offering tangible connections to our maritime past. Let’s explore how to protect their numismatic value and historical significance for generations to come.

Why Saltwater Treasures Demand Special Care

Artifacts rescued from Davy Jones’ locker face preservation challenges that would make most collectors shudder. Take silver coins from wrecks like the Concepción (1641) – their sulfide-based toning developed over centuries creates breathtaking rainbows but hides chemical vulnerabilities. While gold items like the Douro sovereigns boast remarkable resilience, even they can fall victim to micro-corrosion invisible to the naked eye. And that stoneware pot from the Golden Fleece? Its ceramic body requires completely different care than metallic treasures. Material matters – and so does understanding each artifact’s unique journey.

Toning vs. Destruction: Reading the Signs

When Mexican 8 reales from the Reigersdaal (1747) emerge from their briny graves, they often showcase nature’s artistry – concentric rings of iridescent toning that collectors rightly cherish. This natural sulfide patina forms through chemical poetry written in seawater minerals over centuries. But how do we distinguish desirable character from destructive corrosion?

• Collector’s dream: Even gradients with eye appeal that enhance numismatic value
• Conservator’s nightmare: Crusty verdegris (those heartbreaking green silver chlorides) or powdery white lead carbonates

The Ptolemaic tetradrachm from Ashkelon perfectly illustrates this delicate balance – its stable patina whispers of ancient Mediterranean trade routes, while less fortunate artifacts succumb to destructive “bronze disease.” Proper storage stops harmful reactions while preserving provenance-rich surfaces.

PVC Peril: The Silent Collection Killer

“My son’s first 1733 fleet find developed oozing green residue within months of encapsulation” – Heartbroken Forum Collector

Polyvinyl chloride holders remain the Trojan horse of numismatic storage. As plasticizers break down, they release acidic gases that commit three cardinal sins:

• Etching irreversible corrosion into silver (as seen on Reigersdaal pieces)
• Clouding gold’s legendary luster with hazy films
• Degrading organic materials like the Golden Fleece’s precious documentation

This insidious damage often appears months after encapsulation – a delayed heartbreak for unsuspecting collectors.

Preservation Strategies That Work

Archival Storage: Your Collection’s First Defense

For silver cobs like those from the Santa María de la Consolación (1681):

• Acid-free trays with tarnish-resistant linings (preserve that prized shipwreck patina)
• Inert Mylar or polyethylene flips (never PVC!)
• UV-filtering display cases with humidity controls (museum-grade protection)

Gold coins like the Douro sovereigns demand different care:

• 23-karat gold-lined capsules (protect surfaces without chemical reactions)
• Archival plastic tubes for bulk storage (maintain mint condition finds)
• Avoid moisture-trapping felt boxes (a common collectibility killer)

Creating the Perfect Environment

Stability is key – even modest fluctuations can harm rare varieties. Follow these guidelines:

The Cleaning Conundrum: To Intervene or Not?

Every week, collectors ask me: “Should I clean my shipwreck artifact?” The answer will make your conservator’s heart sing: almost always no! Especially for provenance-rich items like the Golden Fleece pottery with its original certificate. But exceptions exist…

When Professional Conservation Becomes Essential

• Active corrosion spreading like wildfire across silver surfaces
• Salt blooms threatening ceramics (as seen on some Ashkelon pieces)
• Organic growth compromising structural integrity

That crusted 1877-S Douro sovereign required electrolytic reduction – a far cry from amateur cleaning. Remember: true conservation enhances collectibility without erasing history.

Cleaning Methods That Destroy Value

• Abrasive polishing: The cardinal sin that erases original surfaces (common with Potosi cobs)
• Chemical dips: Strip protective patinas, leaving coins vulnerable
• Ultrasonic cleaners: Can shatter already fragile structures

“I threw caution to the wind to win that auction – now I’m paying the price in conservation bills!” – Humbled Forum Collector

This collector’s hard-won wisdom underscores why we protect these artifacts: each represents an irreplaceable page in humanity’s story.

Guardians of the Deep’s Legacy

From the Golden Fleece’s humble stoneware to the Douro’s glittering sovereigns, shipwreck artifacts connect us to history’s most dramatic moments. Each Mexican cob from the Reigersdaal embodies global trade’s birth pangs, while Ashkelon’s Ptolemaic tetradrachm whispers of Cleopatra’s world. By embracing these techniques:

• We preserve numismatic value AND historical truth
• Maintain crucial archaeological context
• Ensure future generations can hold these time capsules

As the conservator who first documented the Reigersdaal coins, I implore you: Your stewardship matters. These artifacts survived tempests, pirates, and centuries submerged – don’t let them perish in careless storage. With proper care, your Mexican pillar dollar or Golden Fleece pottery will continue telling its story long after we’re gone. That’s not just preservation – it’s time travel made tangible.

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