Cleaning bronze coins can bring out their details and beauty, but it’s important to be cautious to avoid damaging the coin or diminishing its potential value.
Here are some approaches for cleaning bronze coins, from the most gentle to those requiring more care:
- Rinsing: A simple rinse under running distilled water can remove loose dirt, [according to Coins Auctioned] . Avoid rubbing to prevent scratching. Pat dry with a soft cloth or paper towel – avoid using heat.
- Soaking in distilled water: For coins with stubborn dirt, soaking in distilled water for several days to weeks can loosen debris. Change the water daily and gently brush with a soft toothbrush to help remove dirt and corrosion. Distilled water is preferable as tap water contains minerals that might react with the coin’s metal.
- Dish soap and warm water: Mix a small amount of mild dish soap in warm water and gently clean the coin with a soft brush or sponge. Rinse thoroughly with distilled water and air dry.
- Olive Oil Soak: For common bronze coins, soaking them in olive oil can help remove grime without disturbing the patina. Avoid using virgin olive oil as it might tarnish the metal. After soaking, pat dry with an oil-absorbent material like a paper towel.
- Baking soda paste (gentle scrubbing): Make a paste with a small amount of water and baking soda. Apply it to the coin with a soft brush and gently scrub, then rinse and dry thoroughly.
- Vinegar and Salt Paste (for removing tarnish/patina, but use with caution): Mix 2/3 cup vinegar and 2/3 cup flour in a glass bowl, add 1/2 cup salt, stir to combine. Spread the paste on the coin and let it sit for 1-2 hours. Rinse well and buff dry with a soft cloth. Note that acids like vinegar can remove patina, which some collectors value.
- Electrolysis (advanced method): This technique can remove heavy corrosion and encrustations but requires specialized equipment (power supply, alligator clips, stainless steel anode, salt, water, possibly lime juice) and understanding of the process. Connect the positive terminal to the stainless steel and the negative to the coin. Submerge in a salty water solution with lime juice, and run the process, ensuring the coin is not damaged by the process. It is important to be in a well-ventilated area, preferably outdoors, as the process may release gases, according to YouTube.
- Consulting a professional: For rare or valuable bronze coins, it’s highly recommended to consult a professional coin conservator or dealer. They can assess the coin’s condition and apply appropriate cleaning or conservation techniques without damaging its value or historical significance.
- Ultrasonic cleaning (professional use): Ultrasonic cleaners use high-frequency sound waves to dislodge dirt and grime. Kemet International states this method is often used by museums and collectors as it is gentle and effective.
- Patina: Patina, the natural toning that develops on coins over time, is often desirable and can increase a coin’s value. Removing it can reduce the coin’s value, particularly for collectible coins.
- Abrasives and harsh chemicals: Avoid using abrasive cleaners, wire brushes, household cleaners, or metal polishing cloths, as these can scratch, damage, or chemically react with the bronze, diminishing its value.
- Handling: Always handle coins by their edges to prevent transferring oils and acids from your skin to the coin, [says Real Simple].
- Storage: Store cleaned coins in a dry, cool environment in acid-free holders like coin flips made from inert materials, or airtight containers, [notes Coins Auctioned].
Remember, when in doubt, seek professional advice to preserve the condition and value of your bronze coins.
How to make bronze coins shiny?
Great question! If you stil think you want to clean your ancient coin then, Soak in soapy distilled water but never use lemon juice or vinegar on Bronze coinage. Baking Soda can help clean the coins when they are soaked in soapy water.
How do you clean badly tarnished bronze?
Step 1: Mix 2/3 cup vinegar and 2/3 cup flour in a glass bowl.
Step 2: Add 1/2 cup salt and stir.
Step 3: Spread on tarnished metal. Wait 1 to 2 hours.
Step 4: Rinse, dry and polish with a soft cloth and a dab of olive oil.
How to clean dull bronze?
Great question! Bronze Sculptures can be cleaned with soft brushes and cloths, using water and perhaps a little dishwashing soap such as Ivory Liquid. A simple hose spray or very light pressure washing would be fine and a good way to get into undercuts and crevices.