How to clean bronze sculpture

Bronze sculpture is best enjoyed in as near to perfect condition as is reasonable or possible - in our opinion, a great sculpture that is well-cared for should appear identical to how it appeared when first leaving the artist's studio.  A properly maintained bronze sculpture will remain beautiful in perpetuity - and with very little difficulty!  Check out our article on "how to care for your bronze sculpture" to learn how to easily maintain your bronze sculpture. 

But frankly not all bronze sculpture has been well cared for or properly maintained and over time the layers of grime, dust, nicotine and dirty or excessive wax can become distracting.  The care and cleaning of bronze sculpture is a complicated subject with many nuances and is a topic we field questions on regularly.  Before ever attempting to clean your sculpture, first consult with a professional to get an opinion on value, rarity, risks and for advice on how to proceed.

What is bronze rot and what steps should I take to avoid it?

Bronze rot is a reaction between chlorine and the metal that results in a white powdery residue that is an absolute nightmare to deal with. It is generally brought on by cleaning the sculpture using tap water, where even the slightest trace of chlorine left on the surface of the bronze will create a long term chain reaction. The steps we recommend to avoid introducing this to your sculpture are:

1. Try not to use water.  Most cleaning can be accomplished by dry polishing.
2. If you must use water, always use purified water with zero chlorine content.
3. Never submerge the bronze or allow water to get into the joints; water should only be used sparingly and in areas where all moisture can easily and completely be removed from the sculpture
4. Make sure your sculpture is always sealed against moisture, generally with beeswax or a beeswax/carnauba mix
5. In the event that you made the mistake and submerged the sculpture, all moisture must be completely dried from the sculpture. A fan, space heater, hair dryer or even use of an oven set on low can help release the moisture from the deep recesses of a lost-wax work, where moisture may have found its way through the body and into a remote appendage of the figure. But it is best to consult a professional at this point, as the reaction between chlorine and bronze is very slow and you may not know for several years if the water has been successfully removed.
   

How do I safely clean the dust and grime from my bronze sculpture?

First, find a clean and well lit working space to safely work on the sculpture. Most bronze sculptures remain in beautiful original condition until they are moved, cleaned or handled - a poorly planned work space can change a dirty sculpture into a broken sculpture very quickly. 

Next, dust the sculpture using a soft toothbrush with masking tape around the plastic parts to prevent scraping. A wooden toothpick or bamboo skewers can be very helpful in cleaning cracks and crevices, but never use metal or any hard substance that could scrape the surface.  And it is good to keep in mind that the "dirt" or grime in the crevices may be wax or pigment applied by the foundry for effect.  Removing this means damaging the sculpture.  Crevices can more safely be cleaned with Q-tips.

Now begin to clean the surface of the sculpture. If the surface is particularly dirty and needs to be washed, one safe method is to use saliva. The enzymes in saliva safely break down dirt while having no negative effect on the patina. Every square inch of the sculpture must be cleaned and free of grime before proceeding to wax. While the process is time consuming if the sculpture is in particularly bad shape, it is imperative to take time and remove all dirt or there is a risk the surface will turn slightly green and hazy under fresh wax if the surface is not perfectly clean.

As you are cleaning the surface with some friction, do not attempt to remove "color" from the sculpture.  There are several types of patina, the most popular being chemical patina, acid-pigment, painted/polychrome, tinted clearcoates and in some cases colored waxes. Often there may be a mixture of these, the artist using colored wax to achieve some transition or effect in the sculpture. We have seen so many scenarios where a client has used a toothpick or some other object to remove "grime" from crevices only to realize that they actually removed a blackened wax covering the golden hue of bronze beneath.

After the bronze has been satisfactorily polished and cleaned of all dirt, grime and residue, clean it with a lint-free cotton cloth to remove any remaining dust.

What is the best wax to seal my bronze sculpture with?

There are many dozens of very good waxes, so much of this has to do with preference. We enjoy working with Liberon’s Black Bison wax in Neutral. It is a nice mix of beeswax and carnauba suspended in mineral spirits and applies very evenly.

How do you apply wax to a bronze sculpture to achieve professional results?

Not unlike polishing a pair of shoes, less is more when waxing a sculpture. I prefer to take a square of soft cotton, like used undershirts or a sock, and gather just a touch of wax on the tip and work it around until it is very thin. Then repeat until the sculpture is covered. I’ve tried other methods, like using a bit of wax inside cheesecloth, but I find that the “dip and rub” method allows me the most control. Q-tips can be used for hard to reach areas (be sure to get Q-tips with a paper column and a full head of cotton versus the cheaper plastic variety). A part of the waxing process is actually a cleaning process, so don’t be surprised to see a dirty brown color coming off on your rag as you wax the bronze. The mineral spirits in the wax will cut the old wax on the sculpture and remove the dirt, replacing it with the new fresher wax. Be careful though not to get overly aggressive with “removing old wax”; it is hard not to overstate this: the wax may have some aspect of color for the sculpture that you were not considering.   After the entire sculpture has been sealed, it will begin to haze over - allow it to sit for 20 minutes so that the wax can harden. It should be in a relatively cool area, as it will not harden if left in the sun or other hot space. Then buff it using a clean lint-free cotton cloth until every bit of excess wax is removed from the surface and it glows brilliantly.