Bronze is a beautiful metal and even more so as it ages to a darkened coppery-brown matte finish. It's no wonder that bronze has been used for millennia for decorative and functional items, ranging from jewelry and sculpture to coins and musical instruments.
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Bronze is also hard-wearing, and it generally requires minimal upkeep beyond the occasional dusting. Cleaning antique bronze calls for a careful approach. Understand that its natural patina is desirable and not something to be polished away. Cleaning verdigris, a blueish-green layer on the surface of bronze, requires a more aggressive solution.
Consider Your Cleaning Options
Before cleaning antique bronze, determine the level of attention your item requires. First, know that a darkened, dull finish, which can range from a warm gold to a blackish hue, is natural for bronze. Don't attempt to polish bronze to a bright shine similar to brass. For antique collectors, the dull patina is highly desirable, and overly aggressive cleaning or polishing that removes it would be considered damage. It's easy for someone who isn't an expert to mistake the natural patina for a layer of dirt.
Experts recommend cleaning antique bronze using the gentlest approach possible. This might be dusting, wiping with soapy water or – at the most – minimal polishing with a mild abrasive. You should also finish with a layer of clear paste wax to keep antique bronze looking its best. Use whichever of these options best retains the natural patina.
Verdigris, which is easily identified by its turquoise color, is a natural occurrence when bronze is exposed to moisture. You'll recognize it from the facade of the Statue of Liberty or markings on some old pennies. In some cases, the color is desirable, but more often, cleaning verdigris from antique bronze is essential. Doing so is possible using DIY methods, but if your antique bronze item is especially valuable or you care about its resale value, it's best to consult a professional before tackling verdigris removal.
The Gentlest Method: Soap and Water
Use soapy water to clean antique bronze items that have visible surface dirt beyond just dust. Fill a sink or bowl with warm water and swish in just a squirt of gentle dish soap. Do not plunge the item into the water even if it's small. Instead, soak a soft cotton rag in the water, squeeze it out and wipe down the item with the soapy water. Re-soak the rag frequently as you work and if necessary, use a soft toothbrush to get the soapy water into any awkward crevices.
Following the soap and water step, rinse the rag with clean water and wipe down the bronze item again to remove any soap residue. Dry the item immediately with a towel. If it's difficult to get off all the water drops, use a hair dryer on a low setting to dry the bronze item more quickly.
Cleaning Verdigris and Tougher Stains
Verdigris removal and tough stains that won't wash away with soapy water call for a more aggressive approach but remember to still be as gentle as possible. You shouldn't use any commercial metal polishes, which are too abrasive, but there are some DIY solutions to consider. If possible, test your chosen solution on a small, inconspicuous area first to make sure it's effective and doesn't damage the natural patina.
Some DIY bronze polishes suitable for cleaning verdigris and tough stains include:
- Regular toothpaste
- A thick paste of baking soda and lemon juice
- A thick paste of equal parts table salt, white flour and white vinegar
- A cut lemon pressed into table salt
Use a soft rag or old toothbrush to apply the paste to the bronze item or use the cut lemon as the scrubber. Rub gently with a circular motion until the verdigris or stains are gone but stop before you remove any of the natural patina. Following successful stain or verdigris removal, rinse the item with a water-soaked cloth and dry thoroughly.