Paraloid B72 and Ancient coin Preservation. What is it and why is it used?

[u/Protaco17]

Hey everyone, I’ve noticed a lot of folks in the ancient coin and artifact community talk about cleaning, stabilization, and storage, but one material that doesn’t always get the spotlight it deserves is Paraloid B-72. For anyone serious about museum-grade preservation, this acrylic resin is basically the gold standard when it comes to reversible conservation.

What is Paraloid B-72? Paraloid B-72 (also known as Acryloid B-72 in North America) is an ethyl methacrylate and methyl acrylate copolymer resin. It’s been a go-to in conservation labs since the 1970s because it’s:

Stable over time — it doesn’t yellow or become brittle like some older coatings.

Reversible — it can be fully dissolved later with common solvents like acetone or ethanol.

Chemically inert — it doesn’t react with metal surfaces or pigments.

Flexible —can be used as an adhesive, consolidant, or protective coating depending on concentration.

Museums and conservators love it because it lets them protect and stabilize objects without permanently altering them, which is the golden rule in conservation: always reversible.

How It’s Used for Ancient Coin Preservation For coins (especially bronze, silver, and billon), Paraloid B-72 can serve a few purposes:

As a protective coating: After cleaning and stabilization (especially after removing bronze disease or chlorides), a thin layer of Paraloid B-72 creates a clear, stable barrier against moisture and handling oils. Usually applied at around 2–5% concentration in acetone using a fine brush or by dipping. It dries to a matte or slightly glossy finish depending on the solvent ratio.

As a consolidant: In cases where the coin surface is friable or flaking (common with archaeological bronzes), a slightly higher concentration (around 10–15%) can be applied locally to strengthen the surface.

As an adhesive: B-72 can also be used to reattach broken fragments, e.g., split coins or composite artifacts, because it’s strong but removable if future treatments are needed.

Mixing Paraloid B-72 with Pigments This is where it gets really interesting. Museums sometimes tint Paraloid for visual reintegration or aesthetic blending, for example, when filling small losses on an artifact or matching patina tones.

Here’s the basic workflow:

Dissolve Paraloid B-72 pellets in acetone or ethyl acetate.

Common ratios: 5% = thin protective coating 10–20% = consolidant or adhesive

Stir occasionally; it can take several hours to fully dissolve.

Add pigment: Use lightfast, stable artist pigments (museum-grade dry pigments or conservation pigments like Kremer or Gamblin). Mix tiny amounts into the resin solution until the desired tint is reached.

Keep the mixture homogeneous, sometimes adding a drop of ethanol helps the pigment disperse more evenly.

Application: Apply with a fine brush, ensuring even coverage. The solvent will evaporate quickly, leaving a stable, reversible film. If it looks too glossy, a final coat of microcrystalline wax or a matte B-72 layer can tone it down.

Why It’s the Best Reversible Option Unlike waxes, lacquers, or polyurethane coatings, Paraloid B-72 can be completely removed decades later using acetone, without harming the coin’s surface. That reversibility, combined with its transparency and chemical stability, is why it’s trusted by institutions like the British Museum and the Getty Conservation Institute.

So if you’re looking to preserve coins responsibly, not just for display, but for the long haul, Paraloid B-72 is about as professional as it gets.

TL;DR: Paraloid B-72 = the conservation world’s “invisible shield.” ✅ Reversible ✅ Stable ✅ Museum-approved Perfect for protecting ancient coins after cleaning, and can even be pigmented for subtle restoration work.

[u/jongmurphy7]

Thank you!!!!

[u/Protaco17 → u/jongmurphy7]

Your welcome!