There are a few reasons why you should clean copper, and a few ways to do it. Like most metals, copper is bound to tarnish, and this process inevitably changes some of its properties. From copper jewelry to utensils, cleaning the tarnish will bring back the gorgeous original luster of copper.
When clean and polished, copper has a distinctive red-orange color and bright luster. This makes it appealing for decorative metalwork, as well as cookware and jewelry. Additionally, due to its antibacterial and alkalizing properties, copper can be especially useful for making copper-infused water, by storing it in copper vessels.
However, like most other metals, copper reacts with the environment and tarnishes. So, you might notice it turning black or even corroding, forming a blue or green patina. While in some cases the aesthetics of this patina is highly prized among artists, caution should be exercised to avoid bringing patina into contact with acidic substances such as acidic liquids or food. Failing to exercise care in this regard can be harmful and can lead to copper toxicity.
Therefore, it is paramount that you clean your copper regularly especially if you are using them to prepare acidic foods. Cleaning it will not only bring back its luster but will also prevent corrosion. Additionally, if you use copper vessels for storing water, the process of cleaning them will contribute to their effectiveness, as it reveals unreacted layers of copper.
In this article, you will learn why copper tarnishes, why you should clean it regularly, how you can clean it, and how you can prevent it from tarnishing.
Why Copper Tarnishes
Copper is a reactive metal. In a process called oxidation, copper reacts slowly in the presence of oxygen, resulting in copper oxide. This is what we call tarnish, which is generally perceived as a brown or black coloration on the surface.
This process is natural, and it can be left to further develop in the formation of patina, copper’s protective layer, which can manifest in aqua-green or blue coloration. The patina is a sign of age, and it is highly prized as it raises the value of copper metalwork and protects copper from the elements (think Lady Liberty).
Because of this, some artists even treat copper surfaces with acetic acid to form copper acetate, also known as verdigris. Verdigris gives copper a green color, but it is not as durable as natural patinas, and it is soluble.
In the case of everyday copper utensils, copper is most likely to form a brown or black tarnish in the presence of oxygen, moisture, human touch, dust, and certain chemicals. This tarnishing can further develop, leading to corrosion (or patina), which is usually green. Furthermore, heat and acidic compounds, found in foods like milk, vinegar, or wine, can also induce instant corrosion (known as verdigris).
Copper tarnish is inevitable, and it is facilitated in the presence of the aforementioned circumstances. So, let us see how and why these circumstances affect copper:
The most natural, and inevitable, type of copper tarnish happens in the presence of oxygen. Copper and oxygen ions react to form copper oxide, but, if only restricted to dry air, this process is very slow.
Moisture catalyzes the oxidation process, enhancing the reactivity of copper, and leading to corrosion or patina. This is why it is recommended to wipe off water from washed copper utensils instead of letting them dry on their own.
The oils present on our skin are responsible for one of the quickest ways in which copper can tarnish. While touching certain copper items (such as utensils or jewelry) is inevitable, this also calls for more regular cleaning.
Dust particles are made of dead skin cells and debris from both humans and pets. The debris can contain chemicals which react with the copper, making it tarnish more quickly.
Acidic substances react with the surface of copper, causing it to tarnish and corrode almost instantly. This corrosion is highly soluble, leading to the presence of toxic copper salts in the food. This is why it is not recommended to use copper vessels for foods high in acidity, such as milk, wine, or vinegar.
Heat and Chemicals
Heat and certain cleaning products can also cause copper to tarnish. Heat makes copper more reactive, while some products contain substances which react with copper. Because of this, it is not recommended to place copper utensils in the dishwasher but rather clean them in more copper-friendly ways.
Why It Is Necessary to Clean Copper
Because of its tarnishing and corrosion processes, copper can become less appealing, less reactive, and even dangerous. Depending on the object and the way you use it, cleaning copper can be especially necessary to avoid copper toxicity, which occurs because of the presence of copper salts such as blue vitriol (bluestone), copper sulphate, and verdigris.
Copper cookware like pots and pans are usually lined with another metal on the inside to avoid copper’s reactivity when heated. The copper here is used for better heat distribution and aesthetic reasons. If the lining is damaged and the copper is exposed to the food you cook, you should immediately have it repaired or throw it away.
Otherwise, cleaning copper cookware is desirable because of aesthetic reasons. Copper tarnish can give the cookware a dirty look, and cleaning it will bring its luster back.
Copper vessels for storing water, such as copper pitchers, bottles, or mugs, are not usually lined on the inside. This is because of the beneficial properties of copper ions which diffuse into the water over time.
However, in the presence of water, copper is bound to tarnish more quickly. This covers it in copper oxide, making the copper surface less reactive and, thus, lowering its effectiveness.
While it is not harmful to drink water from a copper vessel with tarnish in the short and medium term, it should be avoided over a long period. Instead, clean your copper vessel every few weeks to remove the patina and increase its effectiveness.
Being mostly in touch with human skin, copper jewelry can develop tarnish very quickly because of the oils present on the skin. This can make it less appealing, and the patina can also color your skin green.
So, cleaning your copper jewelry will not only make it more appealing but will also prevent your skin from turning green in the presence of patina.
How Often You Should Clean Copper
This answer depends on the purpose for which copper is being used. In the case of cookware, you can clean the pots and pans as soon as they tarnish or leave them to tarnish on purpose to achieve an aged look.
However, when copper gets in touch with your water, like in copper vessels, or your skin, like in jewelry, you should make copper cleaning a more regular practice.
The Ways to Clean Copper
There are quite a few ways you can clean copper, from using conventional store-bought products to using home-made cleaning solutions. These substances usually contain a mild acid, which reacts with the copper surface to create soluble copper salts which can be washed off.
If the copper has a lacquered finish, all you need is some water and dish soap to remove dust and grime. You will recognize lacquered finish on copper which is glossy and shiny and does not tarnish over time. If, however, this finish has been damaged, you will notice tarnished spots. Cleaning lacquered finish is very difficult, so your best bet would be to remove it entirely and follow the steps below.
However, you should never clean your copper utensils in a dishwasher, as the harsh chemicals used in some dishwashers can shorten their lifespan. Also, you should never use cleaners which contain bleach, as it can cause the copper to corrode and pit.
Instead, you can try out some of the following copper-friendly ways to clean your copper items:
Store-Bought Copper Cleaning Products
There are many different products which are specially made for cleaning copper. They usually come as creams or pastes, allowing for a thorough cleaning which does not damage the copper.
However, such products can be expensive and filled with chemicals. If you are in a pinch, you can also try to clean your copper in more natural ways with household items which may be laying around your kitchen.
Natural Ways to Clean Copper
You can clean your copper items with the help of household items which may be just within arm’s reach. From ketchup to vinegar, these items have two things in common: they are acidic, and they do not scrub or scratch the surface of the copper.
In fact, you should avoid scrubbing the surface, because this will damage the copper finish, giving the item a scratched and damaged look.
Here are some ways you can clean copper using natural ingredients:
The acidity of ketchup is useful for a quick clean of lightly tarnished copper. All you need to do is cover the copper item in ketchup, let it sit for a while, and then rub until the tarnish has vanished. Finally, clean the copper with warm water and some dish soap and polish it with a clean, soft, dry cloth.
Like ketchup, Worcestershire sauce has acidic properties which can take away the tarnish from copper. Apply it on the copper surface, let it sit for a while, and then gently rub the tarnish off. Finally wash the copper with warm water and dish soap and wipe the water off with a cloth.
The paste from the tamarind fruit is acidic, reacting with the copper to remove any tarnish and restore luster. Rinse the copper surface and scrub it with the tamarind pulp until the luster returns.
White Vinegar and Salt
Dissolve 1 ½ teaspoons of salt in 1 cup of white vinegar. You can put this mixture in a spray bottle or apply the mixture with a soft cloth. Once applied, leave it to take effect for around 30 minutes and rinse and dry. If there is more tarnish present, repeat the process, and if there are dents holding any grime, use a soft toothbrush to gently scrub the copper.
Lemon Juice and Baking Soda
This is a mildly aggressive method, where you need to mix several teaspoons of lemon juice with 1 or 2 tablespoons of baking soda. Use a soft cloth to apply the mixture on the copper surface and rub it gently. Finally, rinse with water and polish the copper with a soft cloth.
Vinegar, Salt and Flour Polish
If you are dealing with more stubborn tarnish, you can try to polish the copper with this mixture. Mix 3 tablespoons of flour, 3 tablespoons of salt, and enough vinegar to form a loose paste.
Spread the mixture thickly onto the copper surface with a soft cloth, giving it a bit of buffing as you spread it. Place the item in a plastic bag or cover it with plastic wrap and let it sit for a few hours (or even overnight). Finally, rinse the paste off and dry the copper item with a soft cloth. Repeat if necessary.
Lemon Juice and Cream of Tartar
This method is moderately aggressive and needs to be used only if you are dealing with stubborn or tough stains, as the abrasive action of the cream of tartar can scratch your copper.
Mix the lemon juice and the cream of tartar to make a paste that is just thin enough to easily spread onto the copper surface but thick enough to cling to it. Apply it and let it sit for around 5 minutes. Finally wash the copper with soap and water and rinse and dry.
Lemon and Salt
For especially badly tarnished copper, you can use half a lemon and some ordinary table salt. This method involves some effort, but it is most effective for removing stubborn tarnish.
Pour some salt onto a plate (coarse salt if you are dealing with tough tarnish), dip the lemon half into the salt, and scrub the surface until you remove the tarnish. Finally, rinse with warm water and soap and dry the copper with a soft cloth.
Cleaning the Inside of a Copper Bottle or Other Copper Vessel
To clean tarnish on the inside of a copper bottle or other copper vessel, you can create a mixture of the juice of 1 lemon, 1 tablespoon of salt, and ½ cup of water. Pour the mixture in the vessel, close the lid, and shake vigorously. Pour the mixture out and rinse the vessel with water. Finally, dry it if you are not going to store water in it.
How to Keep Copper from Tarnishing
To keep copper from tarnishing, you need to eliminate the circumstances which make it tarnish. Of course, exposure to air will eventually make it turn darker, but this is a very slow process.
On the other hand, controlling the rest of the factors is paramount in preventing unnecessary tarnish. So, keep your copper objects dry and store them in a dry place. After washing copper objects, do not let them dry on their own.
If you live in a high-humidity area, you can place small copper items in plastic bags with a silica-gel packet.
Wipe the copper dry and clean and polish it after using it or touching it, and do not place it in a dishwasher under any circumstance.
If you have a copper vessel for storing water, make sure you keep it in a dry place whenever you do not keep water in it.
Additionally, you can coat your copper object by wiping it with a light coat of baby oil, mineral oil, olive oil, WD-40, or even a thin layer of carnauba wax or beeswax.
For copper jewelry, you can also coat it with clear nail polish or buy a copper lacquer to spray on.
The Bottom Line
Copper is beautiful to look at and healthy to use in copper vessels and other items, such as copper tongue scrapers or copper jewelry. However, tarnish can affect the luster and even lead to corrosion.
This is why you should take regular care of your copper, cleaning it every once in a while. Copper tarnish is inevitable, but there are many easy ways you can clean it and prevent it. However, do not coat your copper vessels on the inside if you are aiming to enjoy the health benefits of copper.
About the Authors: This article was collaboratively written by our team of researchers and writers with the benefit of all available scientific studies and other relevant literature. Our team of researchers and writers include experienced health researchers including a qualified medical professional. Please note that information in this article is not intended or implied to be a substitute for professional medical advice, diagnosis or treatment.