CLEANING COPPER AND BRONZE

Copper is the trickiest metal to work with. The goal: remove "bronze disease" while preserving the patina.

🚫 What NOT to do

• **Ammonia** — turns copper blue and breaks it down
• **Strong acids without monitoring** — the coin turns pink and crumbly

Method 1: Phosphoric acid

Works ONLY on copper, not silver.

• Mix acid with water (concentration by eye)
• Soak for **45 minutes** — don't over-soak!
• Remove and rinse. Light rust flakes off, and the design becomes sharper.

Method 2: Azelit (rust remover)

• Soak for **literally 1 minute**
• Removes blackening very well, very gentle

Method 3: Fiberglass brush in water

• A frayed brush, a bowl of soapy water
• Clean underwater, changing the water as it gets dirty
• Don't press hard — won't damage the coin

Method 4: Pemoluxe (abrasive cleaner)

Can be used dry or wet. Good results, but be careful with pressure.

🦠 Bronze disease (green powder)

Copper chlorides. Treatment:

• Mechanically clean out the affected spot
• Heat/anneal the piece
• Apply BTA (benzotriazole)
• Seal with wax or Paraloid B72