Anyone who has visited the Statue of Liberty in New York or has seen it in a picture knows that copper turns green when exposed to the elements. Copper oxidation is a common problem, but the green patina that forms on the surface of the metal is something that can be removed with simple ingredients.
Why Does Copper Turn Green?
Copper is a metal used in many household materials such as pipes, home hardware and doorknobs. It's most commonly found in pennies but is also used in jewelry, cookware and other products that people use every day. Copper is a beautiful burnished-gold color when it is clean and well maintained, but like all metals, copper can become discolored when exposed to air and water.
The process of the change in color of copper when it is exposed to air is called "oxidation." Oxidation typically turns copper black, which is evidenced by dirty-looking pennies that have been passed around for a long time. When copper is exposed to water, it turns a bluish-green color, like the Statue of Liberty or the roofs on old mansard buildings.
Despite the fact that it looks like something is wrong, the process of oxidation is a protective measure. The discoloration is actually a shell that forms over the copper's surface in order to protect it from breaking down or being destroyed by the elements. While some people like the look of the bluish-green color that exposure to water brings, if you use copper in your home, you probably want to keep it clean.
How Do You Remove Oxidation From Copper?
Despite the dismay that many people feel when they see that their beautiful copper pipes or copper cookware have turned green or black, there is a comfort to be found. You can remove oxidation from copper, and it is a fairly simple process if you have the right tools. Even people who have never cleaned copper before will be able to remove oxidation from copper with little trouble.
The trick to keeping copper clean and bright is regular maintenance. If you clean copper once and then get it wet again, it will, of course, get oxidized again. The same is true of its exposure to air. The best defense against copper oxidation is to clean it regularly using the appropriate materials and ensure that you are doing your best to protect it from the elements between cleanings.
How to Clean Corrosion Off Copper With Salt, Vinegar and Flour
One of the most popular ways to clean corrosion off copper is also one of the cheapest. It requires household items like vinegar, salt and flour, which you most likely already have on hand. For signification corrosion on the copper, make a paste of equal parts vinegar, flour and salt. Rub it all over the affected area and allow it to sit for about 30 minutes.
Once the paste has sat for a while on the affected metal, wipe it clean with soapy water and dry it well. Salt has metal cleaning properties all on its own as well. If you have stubborn copper oxidation due to exposure to air and water, cover the surface of the copper with salt and begin to rub it vigorously with a soft rag. Keep rubbing until the bluish-green discoloration has disappeared.
How to Clean Corrosion Off Copper With Ketchup
It may surprise some people, but ketchup is actually an excellent copper polish. The acid in the tomatoes plus the vinegar and salt that are already included in the product can beautifully clean the stain off copper. Rub ketchup all over the affected area and leave it there for 20 minutes before buffing it clean with a soft, damp cloth.
Once you've finished cleaning the oxidation from the exterior of the copper object, rinse it with warm water. After rinsing, be sure that you promptly and completely dry the object with a soft cloth. By keeping it dry, you remove the risk of new blue-green oxidation building up again right after you cleaned it.
Other Household Cleaning Methods
Depending on the extent of the oxidation on your copper object, salt, vinegar, flour and ketchup alone may not be enough to get your copper shiny again. Once you've tried those methods, if it's still not working, you can cut a lemon in half and cover the surface with salt. Rub the salted lemon half all over the copper oxidation, using it as a scrub brush. Scrub until the surface is shiny or until you've removed as much oxidation as seems possible.
If there is still oxidation after using the lemon and salt method, there are further steps you can take. Take the other half of the lemon and squeeze it into a jar or bowl. Add a few spoonfuls of cream of tartar and stir to make a paste. Apply the paste to the copper object, covering all affected areas. Leave the paste on the surface of the copper for at least one hour and up to two. Then, wipe the surface clean.
If nothing removes all traces of oxidation, and there is still either blackish or bluish-green tinting on your copper, you can try to boil it away. Place the copper object in a pot of water that you have brought to a boil. Boil the object until the very last of the tarnished bits have fallen away. You may need to scrub it with salt after taking it out of the pot, but the boiling water should remove the lion's share of the remaining tarnish.
Other Copper Cleaners and Copper Polish
While there are commercial cleaners that cleanse metals like copper, brass, silver and gold, they are not necessary unless you find that you are having no luck with the natural methods. Generally, commercial cleaners are merely a harsher chemical version of these natural methods. However, if you are unable to clean the copper objects with the natural methods, then they are a good option.
It is a good idea to call a hardware store and ask what they recommend. If you describe the type of copper item you are trying to clean, they will often be able to recommend a product. If you are trying to remove oxidation from copper or brass jewelry, it may be a good idea to call a jeweler. Jewelry can be very delicate, and although oxidation protects the metal from corrosion, it may be difficult to get it out of delicate places without harming the integrity of the jewelry.
How to Care for Copper
It can be nearly impossible to prevent copper pipes, cookware and hardware from coming into contact with oxygen and water. In the case of pipes and cookware, contact with water is a key part of the object's usage. However, while oxidation is a protective layer and not evidence of damage, most people do prefer to have their copper shiny and clean looking.
In order to care for copper properly, it's important to understand it. Copper is a metal alloy and a soft metal at that. This means that scrubbing with Comet or another abrasive commercial cleaner that is too harsh can damage the copper's surface, leaving scratches. This may not be a problem for cookware when you are more concerned with cleanliness than appearance, but it is good to keep in mind when cleaning jewelry.
Copper is also susceptible to bending and warping if too much pressure is applied. To protect copper from oxidation and further damage, it is a good idea to coat it with olive oil or linseed oil after cleaning it. This oil can help create a barrier that will ward off oxidation for a while and keep your copper looking shiny and new.
Ashley Friedman is a freelance writer with experience working in the home, design and interiors space.