Copper products have remained relevant and popular for several centuries. But their noble appearance is often spoiled by a greenish dull coating that forms on the surface layer due to an oxidative reaction with air. You can clean copper objects from oxides using modern chemical products or simple home techniques. Convenient and non-hazardous cleaning options will return your household utensils and other items to their original shine and attractiveness.
Reasons for the raid
Dishes, furniture fittings, jewelry and other things made of copper need periodic cleaning to remove green deposits. This need is associated with the characteristics of the metal. Due to prolonged exposure to air or exposure to temperature, such things become covered with a dark greenish film. Oxides are especially noticeable on dishes that are constantly used in the kitchen. Darkening can only be removed by cleaning.
Jewelry with copper behaves differently. They sometimes darken, but then return to their original state. It is widely believed that this behavior of the metal is a reflection of the health of the owner of the jewelry. In reality, such changes only reflect a reaction to environmental indicators: fluctuations in humidity, pressure or temperature.
Important! Oxides on copper cookware are especially dangerous. If plates and pots are not cleaned for a long time, the metal releases toxic substances that are harmful to human health.
Metal oxidation
Copper in its usual state has a reddish tint. If a metal is exposed to air for a long time, it acquires a red-violet or blackish tint due to a layer of oxides forming on its surface. Prolonged exposure to high humidity conditions provokes the formation of a layer of hydroxides on a copper product. Then a greenish color appears. An acetic acid layer of blue-green color also appears on the copper from contact with vinegar. It is a poisonous substance.
Drawings for RF patent 2329333
Quasicrystals known to date are formed, as a rule, by metallic components, but have a number of properties that are very unusual for metal alloys. These include extremely high electrical resistivity, a significant negative temperature coefficient of resistance, an increase in resistivity with increasing degree of structural perfection of samples with very strong sensitivity to composition (Mayou D., Berger S., et al. // Phys. Rev. Lett. 1993. V.70. No. 25. P.3915), low thermal conductivity and low electronic contribution to the specific heat capacity. At the same time, quasicrystals have a hardness exceeding the hardness of steel, and in their antifriction properties they are comparable to fluoroplastics. The most promising films for use are quasicrystalline films; massive samples are highly brittle, which limits the possibility of their use.
Various methods are known for producing quasicrystalline Al-Cu-Fe films. For example, films 300 nm thick were obtained by layer-by-layer magnetron sputtering on alternating current (Klein T., Symko OG // Appl. Phys. Lett. 1994. V.64. No. 4. P.431), by electron beam evaporation from one alloy cathode films 400-900 nm (Yoshioka A., Edagawa K., Kimura K., Takeuchi Sh. //Jpn. J. Appl. Phys. 1995. V.34. No. 3. P.1606). To obtain a quasicrystalline phase in films prepared by these methods, subsequent annealing is necessary. Without subsequent annealing, quasicrystalline films are obtained only by sputtering onto a heated substrate (Eisenhammer T., Trampert A. // Phys. Rev. Lett. 1997. V.78. No. 2. P. 262).
Cleaning copper products at home
Copper products that are constantly used should be cleaned regularly. A simple rinse under the tap in dishwashing detergent is suitable. Instead, you can wipe down copper items with sanitary gel. If these methods do not bring cleanliness and a significant part of the product remains covered with plaque, more aggressive cleaning methods are used.
Vinegar with salt
In this case, rub the item with a soft cloth using a special product. It is mixed from 1 cup of ordinary vinegar and 1 tbsp. l. salt. After cleaning objects from oxide, they are washed with clean water and wiped thoroughly.
Another method for cleaning copper at home is to boil the item in a solution of salt and vinegar. For it, add 1 glass of ordinary vinegar and 1 tbsp to 3 glasses of water. l. table salt. The copper product is placed in the prepared solution and left to heat up. After 15 minutes of boiling, it is possible to remove all the green deposits. Then the item is taken out and washed under running water with detergent.
Important! This cleaning method is used for copper items with or without a protective coating.
Cleaning with ketchup
This is an easy and affordable method to clean copper products from plaque. In this case, cover the surface of the copper item with the sauce and set aside for 30 minutes. Then polish the surface with a soft cloth, and wash off the remaining ketchup with warm water. This method returns the lost shine to the item. In the same way, you can clean copper utensils from patina using kefir.
Cleaning with salt and lemon
In this way, you can clean a copper basin at home or large copper products until they shine, for example, samovars and pots. Cut the lemon into two parts and sprinkle the cut area with coarse table salt. Then polish the surface of the kitchen utensils.
You can make a special paste for cleaning copper. For it, mix table salt, baking soda and flour in equal volumes, then add lemon juice to form a paste-like mass. This product is used to rub the surface layer of the object until it shines. After cleaning, the item is washed with heated water. As a result, the copper product acquires a mirror shine.
Using Baking Soda
It is convenient to use baking soda to clean copper at home in combination with lemon juice. Use the resulting liquid to wipe the surface layer of the item with a soft cloth and then rinse. Instead of lemon juice, you can clean copper with citric acid dissolved in water and soda.
Another way to use baking soda to clean copper from oxides is by boiling:
- Dilute 1 tbsp in 1 liter of water. l. soda and lower the product completely into the liquid.
- The container is set to heat up and boil for half an hour, after which the heating should be turned off.
- Then the product is washed with heated water and wiped completely.
Important! Using the proposed method, green deposits are removed from a copper product. It is also used to remove damaged varnish on copper items.
Vegetable oil
An excellent means for cleaning copper is vegetable oil. It's even better to use olive oil. This method is good because it is natural, environmentally friendly and harmless. Therefore, it is especially recommended to use it when you need to clean valuable items from oxidation.
To do this, olive oil is poured into a deep container and copper objects are placed in it. After 10 days, they are removed and cleaned with a soft brush or cloth. Then they return to their place. Such actions are repeated every 10 days for two months.
Effective cleaning methods
Today, the arsenal of tools that can be used to clean copper has expanded significantly. Together with ancient vinegar, sand and wire sponges, a large number of both specially designed products and those adapted by folk craftsmen are used. Among the latter there are some quite unexpected ones.
How to clean copper
- Tomato ketchup. Apply a small amount of tasty seasoning to the stain and leave for several minutes. Rinse off with plenty of water.
- In case of light stains, you can try washing them with a regular gel detergent. The gel is squeezed onto a soft sponge and then applied to a copper object. After leaving for a minute, rub the surface and rinse with water.
- Used for large products, such as a samovar. Cut the lemon in half and rub the half over the surface of the product. Next, clean with an elastic fluffy brush and rinse with water.
- Vinegar dough. Mix vinegar and regular table flour in equal parts. Stir until a homogeneous paste-like mass is obtained. Next, the paste is spread in a thin layer on the surface to be cleaned. After waiting for complete drying, remove the product with a rag or wooden spatula. The product must then be polished with a soft cloth.
If the above methods do not lead to success, use the following method:
- Prepare a stainless steel basin or pan.
- Pour vinegar and add a couple of tablespoons of regular table salt. Stir thoroughly.
- Immerse the item to be cleaned in the solution and bring to a boil.
- Remove from heat and leave to cool at room temperature.
- Drain the cooled solution, rinse the copper object and wipe dry.
Cleaning copper with vinegar
If you decide to clean copper, take precautions. The use of protective gloves and glasses is mandatory. If you dilute vinegar essence, you should ensure ventilation of the room.
Use of chemicals
Sulfuric acid removes darkening and green deposits from the surface layer of copper very well. It is mixed in equal proportions with water and a copper bracelet or other objects are placed in the liquid. When the seething begins, take the item out and wipe it well with a soft cloth. Then the item is laid out on a flat surface to dry. This cleaning method returns the product to its original shine.
Important! When working with sulfuric acid and other aggressive substances, put rubber gloves on your hands, and protect your respiratory organs with a respirator.
Another cleaning method is to use the drug Trilon-B. The substance is stirred in water in a ratio of 1:10. Afterwards, the copper product is lowered into the resulting liquid and observed. When the required degree of cleanliness is achieved, the item is taken out and washed with clean water.
Cleaning Copper Coins
Coins made of copper and its alloys are often found in the collections of numismatists. Over time, their appearance deteriorates. A yellow film appears on coins if lead is included in the alloy. You can get rid of such a substance by immersing objects in a vessel with a solution of laundry soap. After 2-3 hours, the coins are taken out and wiped with a rag soaked in table vinegar. After such cleaning they become shiny.
You can remove blackness from copper using citric acid:
- Mix a solution of 200 ml of water and 2 tsp. citric acid.
- Soak a piece of cotton wool with the product and wipe the parts of the coin.
- After cleaning, the products are rinsed well.
Reddish deposits from coins, crosses and bracelets made of copper are removed by treating with ammonia. Things are dipped in ammonia for half an hour, and then washed in heated water.
How to make copper products shine
If you simply clean copper, the stains will go away, but the item itself will not shine. A dull surface can be made shiny using one of the following methods:
- Mechanical polishing with newspaper or printed leaflet printed with black ink only. Rub the surface until the shine is restored.
- Wiping with a weak solution of hydrochloric acid. Precautions must be taken: the room must be well ventilated, and the use of protective gloves and goggles or a transparent face shield is mandatory.
- Mix equal parts vinegar, table flour and regular salt. Stir until it becomes a thick paste. Apply the paste to the cloth and polish the surface until shiny. At the end of the operation, rinse the item with warm water.
Polished copper
To restore the shine to copper products, you should regularly care for them. Then it will be possible to do without the use of strong chemicals that are hazardous to health.
Removing black and green plaque
To degrease the surface and remove the patina, use a mixture of turpentine, oxalic acid and ethanol. A solution is prepared from these equal volumes of funds. A rag is moistened in it and the products are wiped. Another cleaning method is to use crushed chalk and kerosene. The substances are combined to form a thick mass and used to polish objects.
When the layer is insignificant, it can be easily removed with ordinary soap. It is dissolved in water and the entire thing is dipped into the soapy solution. Then polish with a thick sponge.
A greenish and black layer on copper utensils indicates its unsuitability for cooking and preserving food. Such products must be cleaned before use.
Cleaning rust
In addition to plaque of various shades, rust appears in the top layer of copper objects, which is iron oxides in the form of flakes. To remove it, use strong acidic solutions, and to wash products, use a baking soda solution.
An acid solution is poured into a cup made of ceramic, glass or other inert material and the copper product is immersed in it with tweezers. A reaction will begin, during which rust is removed and dark smoke comes out. When the process is complete, the product is carefully removed and placed in a baking soda solution to neutralize the acid. The washed item is thoroughly wiped with a rag.
Important! When handling acid, be sure to protect your hands with rubber gloves, wear a protective mask or goggles and a respirator.
Cleaning a Turk, samovar or kettle
The exterior of this kitchen utensil can be cleaned using any of the suggested methods. The inside is much more difficult to clean. There, objects are oxidized by water, but also covered with a lime layer.
To remove dirt from the inside, potato peelings are used. They are placed in a bowl and poured over with boiling water. Then set the utensils on the fire and boil the cleaning for an hour. Then the contents are poured out, and the utensils themselves are washed in heated water with detergent.
To complete the cleansing, boil plain water several times in a cleaned container. This gets rid of traces of limescale.
Useful tips
To ensure that copper items last longer, they should not be cleaned with abrasives or rubbed with metal brushes. Copper is a fairly soft metal and is easily scratched by hard objects.
It is better to store copper utensils, jewelry, embossing and coins in a special cabinet. It must be dry and ventilated. In such conditions, things made of copper retain their attractive appearance. If objects are kept in constant humidity under conditions of a significant increase in temperature, they quickly lose their attractiveness and become covered with patina.
You cannot cook food containing foods with a high acid content in copper cookware. This renders kitchen utensils unusable. When cookware has a decorative coating, it should not be polished or cleaned with abrasive materials. Such items can only be washed in heated water using a soap solution. Periodically wipe all copper utensils with a clean, soft cloth to prevent dust and soot from settling on them.
Adsorption of oxidizing agent on metal
When a metal enters a corrosive environment, the initial stage of their interaction is the adsorption of oxidizing agents (CO2, H2O, O2, Cl2, SO2) on the metal surface. A strong ionic bond immediately arises between the metal atoms and the oxidizing agent - the metal atom transfers two electrons to the oxygen atom. The oxygen atom is exposed to the field created by the metal atoms. The oxidizing agent is adsorbed on the metal surface, while the inner surface of the resulting adsorption film is positively charged, and the outer surface is negatively charged.
The distribution of oxidizing atoms on the metal surface very much depends on the location of the metal atoms on the surface.
The metal surface is filled with a chemisorbed oxidizing agent almost instantly and a thin layer of the oxidizing substance is formed. At low temperatures, after a chemisorbed oxidizer, physical adsorption of oxidant molecules can also occur due to van der Waals forces.
