Protecting Metal Medals from Oxidation
Quick Tip
Always use a soft microfiber cloth and avoid harsh chemical cleaners to prevent permanent damage to delicate metal surfaces.
You pull a vintage bronze medal from a storage box only to find a layer of green crust—verdigris—eating away at the detail. This happens because metal reacts to moisture and oxygen in the air. This post focuses on how to stop oxidation on your metal collectibles and how to treat it when it occurs.
How Do I Stop Metal Medals from Oxidizing?
The most effective way to stop oxidation is to control the environment by using silica gel packets and airtight storage containers. Humidity is the enemy of metal. If you keep your medals in a way that limits exposure to air and moisture, you'll significantly slow down the chemical reaction that causes tarnish.
A few things you can do right now:
- Use Silica Gel: Drop a few silica gel packets into your display cases to soak up excess moisture.
- Air-Tight Displays:encapsulate your pieces in UV-protected acrylic cases.
- Avoid Skin Contact: Oils from your fingers can leave acidic residue on bronze or silver-plated metals.
I've seen collectors lose way too much value because they left medals sitting out on an open shelf in a humid basement. It's a mistake you don't want to make.
What is the Best Way to Clean Verdigris?
You should use a very mild, non-abrasive method to clean oxidation, often involving a specialized metal polish or a pH-neutral solution. If you see green crusting (verdigris) on bronze or copper, it's often a sign of deep corrosion. You need to be careful—aggressive scrubbing can strip the original patina and ruin the historical value.
Here is a quick comparison of common cleaning approaches:
| Method | Best For | Risk Level |
|---|---|---|
| Microfiber Cloth | Light dust/surface oils | Very Low |
| Silver/Bronze Polish | Removing light tarnish | Medium (can strip patina) |
| Ultrasonic Cleaner | Intricate, non-porous metals | High (if used incorrectly) |
If you're dealing with a high-value piece, sometimes it's better to do nothing at all. A "dirty" medal is often more valuable than a "shiny" one that's been over-cleaned. For more technical details on metal aging, check out the Wikipedia entry on oxidation.
Should I Use Chemicals to Protect My Collection?
You should avoid harsh household chemicals and instead use professional-grade microcrystalline waxes like Renaissance Wax. This product is a staple in the museum world (and among serious collectors) because it creates a thin, transparent barrier against oxygen. It doesn't leave a greasy residue and stays stable over time.
It's a small investment for long-term protection. Just remember: always test a tiny, inconspicuous area first. You don't want to accidentally dull the finish of a prized medal by being too heavy-handed.