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How to clean a coin from cupronickel. Cleaning of copper-nickel and bronze coins of the USSR. The best way. Why does cupronickel darken

Cupronickel (they are also copper-nickel) coins of the USSR are a headache for numismatists, and especially treasure hunters. The process of cleaning them is still something incomprehensible even to experienced numismatists. In truth, these coins do not lend themselves to cleaning at all, since a good result is almost impossible to achieve.

So, what is so interesting about these coins? And copper is interesting in them, which "paints" the surface in red - from light pink to dark brown. In fact, 100 percent of cupronickel coins from the period 1931-1957 that were found in the ground have changed their original silver color. For the most part, among the "dug" coins and there are rare coins and years, rather than they come across in good condition from the bins of fellow citizens.

How to clean copper-nickel coins? Most numismatists will say, they say, they have not yet come up with a good cleaning method. But, you must admit, it's a pity to leave the coins to rot further. In addition, for many people, and for numismatists too, coins depicting a worker with a shield do not seem like ordinary coins that can be put into a drawer and forgotten about them.

After rereading many ways to clean such coins on numismatic forums, I came to the conclusion that, in fact, there is only one cleaning method, which can be called "barbaric", but at the same time it is very effective. Its essence is as follows:

Pour the acetic acid solution into a small flat container. The proportion is as follows - pour 10 parts of water into 1 part of vinegar from a glass bottle sealed with plastic. The depth of the solution should be about 5-7 mm (no need to transfer vinegar).

We find or buy a brass brush or sponge (this is the barbarism of cleaning).

Every 12 hours, gently brush off any softened oxides from the surface of the coin.

We repeat the procedure until the surface of the coin starts to shine like polished silver (don't forget about the edge). Cleaning usually takes 3 to 10 procedures.

Drying the coin (literally) - first rubbed it with alcohol, and then in a warm place (for example, on a sunny windowsill) for several days.

After a certain time, the peeled coin will become a little grayish, and the shine will disappear. After that, you can put the coin into the album. I think after reading this article you will definitely have questions. I will answer them right away:

Are there any scratches on the coins? There are no scratches visible to the human eye (since the brush, although metal, is soft), but of course they are under the microscope

Can all copper-nickel coins be cleaned? In principle, everything, but it all depends on how much the coin has already rotted. According to my statistics, out of 100 coins, about 10 coins are cleaned almost perfectly, and 20 coins are so rotten that their cleaned field looks like the surface of the moon

Will the peeled coins in the album "deteriorate" in the future? As practice has shown, about half of the cleaned coins after six months or a year nevertheless changed their color (most often to rainbow). I associate this with insufficient drying of the coins. So this cleaning method needs some work. But with all this, half of the coins looked quite decent even after a long time.

There are chemical and mechanical cleaning methods. You can also get rid of contaminants by cooking or electrolysis. The choice of a particular method depends on the properties of the metal from which the product is made.

Features of the content of copies

High humidity and exposure to direct ultraviolet radiation are not allowed. Properly storing coins at home means using special organizers. They differ in materials, cost.

  • Albums. They come with a fixed number of sheets and replaceable ones. Suitable for short-term storage. It is recommended to choose plastic options. PVC albums should be avoided.
  • Holders. Cardboard envelopes with transparent walls. Stapled or glued to paper. They need to be replaced with new ones twice a year, which is not very convenient.
  • Envelopes. Popular with novice collectors. There are paper or plastic ones. They are easy to use, budget-friendly, but they need to be changed frequently.
  • Capsules are weak. The most reliable storage methods, but they are expensive. Products are sealed in them hermetically. Above is information about the coin.
  • Cases. They are presented in a wide variety, but have a high cost. Provide the highest quality storage conditions. Shelves are installed in the structure, and coins are placed in separate cells.

Münzcabinets are like briefcases. They are made of expensive wood species. In most cases, they are used not as a functional, but as a status store.

What cannot be influenced

You can clean old coins efficiently and quickly if you know what substances and tools cannot be used.

  • Concentrated solutions... It is not recommended to add large quantities of nitric, acetic, sulfuric or hydrochloric acids. They are capable of melting the embossing and drawing, which will damage the valuable specimen. It is better to treat it with a special agent "Asidol" or use the powder "Trilon".
  • Sandpaper. Dangerous for bronze, copper products, as it destroys the patina. Sandpaper is able to change the relief of the embossed surface.
  • Metal brush. Damages the surface of the coin. It is recommended to use brass, with artificial, natural pile.

Too high temperatures can also destroy the metal.

How to clean your coins: 5 “home” solutions

Chemical reagents can remove rust and oxidation from coins. The main ingredients used are acids, baking soda, ammonia, laundry detergents and soaps. Unlike other methods, removing dirt with hydrochloric acid is a laborious and careful process. It is imperative to carry out an alkali treatment to neutralize the reaction.

Vinegar

Description. It is a fast-acting cleaner for copper coins with a black, yellow coating. The method is suitable only for those specimens that are not of great value. You can give shine to old coins that are not exclusive and rare items. The most convenient option is to put metal money in a 10% vinegar solution. There is another way to get rid of the dirt that has accumulated over the years.

Procedure

  1. Add a small pinch of salt to a quarter cup of vinegar. If you need to process a lot of products, then take half a glass of vinegar and 15 g of salt. Stir to dissolve all the particles.
  2. Place coins in the solution. We make sure that they do not come into contact with each other. We wait five minutes.
  3. We take out. If the dirt has not disappeared, then gently erase them with a brush made of artificial or natural bristles.
  4. We rinse with running water.

Ammonia

Description. A 10% ammonia solution from a pharmacy is suitable. Since it has a persistent, pungent odor, work is carried out in a well-ventilated room. Allows you to clean pink stains from aluminum bronze coins. And also from copper and silver - from green, purple, brown plaque.

Procedure

  1. Pour ammonia into a container. We place products in it. Rotate them periodically. Immediately and abruptly we do not reach it.
  2. After we have finished removing the dirt, gradually pour water into the solution to reduce its concentration of the active substance. When it becomes weak, we take out the metal money and rinse it with water.
  3. Can be wiped clean with a soft cloth or left to dry.
  4. We repeat the procedure if the copies are not cleared the first time. But we do this only for products that are not damaged, for example, chips, cracks.

Soda

Description. Using soda as the main alkaline product, do not forget that it can negatively affect the products. It is recommended to make a weakly concentrated solution and closely monitor the reaction of the metal. Great when you need to remove green plaque from silver coins.

Procedure

  1. We take a spoonful of baking soda and add a little water to it until a gruel forms.
  2. The mixture is applied to the surface of the coins.
  3. Get rid of dirt with a soft brush.

Citric acid

Description. You can clean the coins to make them shine with a budget tool - lemon juice. The solution is capable of having an aggressive effect, so we carefully monitor the reaction.

Procedure

  1. We dilute citric acid in water so that no crystals remain at the bottom.
  2. Place the coins, swap them so that all sides are cleared.
  3. Rinse with water and dry.

Cleaning bimetallic coins involves the use of a solution in which a glass of water is mixed with two teaspoons of citric acid. We keep the products in it for no more than ten minutes. We wipe with a soft old toothbrush.

Soapy solution

Description. One of the simplest and cheapest options. In addition, laundry soap is absolutely safe for collectible items.

Procedure

  1. Pour hot water into a container and rub soap into it. We are waiting for the detergent to dissolve.
  2. We place the products in the mixture. Cover the container with something. We leave for two or three days.
  3. We take out the coins, clean them with a soft old toothbrush.

It is permissible to replace soap with washing powder. But it is only effective for light soiling. We immerse metal products in the solution for several hours. Then wash off with water and dry.

Methods for silver

Dry cleaning is suitable for low-sample products. They are treated with "Trilon B." The solution removes green plaque. More valuable specimens require careful handling. Having decided to polish the coins, we try to process them in such a way that they do not come into contact with each other. After the procedure, be sure to rinse in warm water. Let's consider two non-standard ways.

  1. Water left over from boiling eggs... Suitable for removing light dirt, provides shine. We put money in warm water and let it stand for several minutes. In this way, white Soviet coins can be cleaned. The method is gentle and harmless.
  2. Formic acid. We take a 5% solution and put specimens from the collection into it. Then gently clean it with a soft brush. If this is cleaning USSR coins at home, then the method is effective, since it removes traces of oxidation.

Silver coins should not be immersed in hot water or boiling water, and then immediately rinsed with cold.

For copper

The choice of processing method depends on the color of the patina. If it is cherry, brown, then we use an ammonia solution, if it is yellow, we need vinegar, and white, we use distilled water. There are two ways to clean a copper coin at home from black plaque.

Vaseline oil

  1. Pour oil into a saucepan. (The standard volume of the vial is 40 ml. Therefore, the amount of oil is determined based on the number of coins to be processed).
  2. We put on fire.
  3. Throw the products into the boiling oil and keep them until the plaque disappears.
  4. After digestion, cool them and wipe them with alcohol.
  5. Dry with a soft cloth.

Peroxide + ammonia

  1. For 200 ml of water we take a teaspoon of ammonia, 30 ml of hydrogen peroxide.
  2. We mix the components and place the coins in the finished solution for no more than 15 minutes.
  3. Then gently wipe them with a soft cloth.

Copper coins can be boiled in laundry soap. This is a gentle option that allows you to preserve collectible items without harming them.

For bronze

The same methods are suitable for bronze products as for copper. Consider two more folk methods that have gained popularity among numismatists.

  1. Coca Cola . The drink acts as a dirt dissolver. It holds coins for a week. Then they need to be rinsed in water. Based on the feedback, the results are impressive.
  2. Bath cleaner. We choose products without aggressive components. We lower the products for a maximum of a couple of minutes. Rinse well with water.

You can also clean bronze coins with hyposulfite. A 10% solution is suitable.

For cupronickel

In terms of its properties and characteristics, cupronickel is similar to a noble metal, therefore, over time, it acquires a black coating, oxidizes. The following methods allow you to return the shine to products without damage.

Dish cleaning powder

  1. We wet the products in water, apply the product to them.
  2. With a soft sponge, rub the surface on both sides.
  3. Leave it on for a few minutes and rinse it off.

  1. If there is a smoking person in the house, then we collect ash from tobacco products.
  2. Dip the coins in water, sprinkle with ashes.
  3. We hold for 20 minutes and rinse.

Any cleaning of cupronickel coins, like the processing of other metals, requires compliance with safety rules. Do not forget about hand protection - put on gloves.

3 radical techniques

It is possible to clean the royal copper coins, silver, cupronickel, bronze items of different years of issue in radical ways. Mechanical method, digestion, electrolysis are options with a high risk of damage to the surface of products. They can be used by those numismatists who have sufficient knowledge and practical experience.

Mechanical impact

Metal products are processed using the following tools:

  • non-rigid brushes with artificial, natural bristles;
  • scraper;
  • sewing needles;
  • medical scalpels;
  • cuts of materials (cotton, suede);
  • drills.

The main difficulty is to remove dirt without scratching the surface. But in the absence of experience, small patterns can also be erased, which will ruin the entire copy.

Digestion

Description. Metal products are processed with boiling liquids. The main component is vaseline, linseed, olive oil.

Procedure

  1. Using a special mesh or tweezers, we immerse the product into the composition.
  2. We boil for no more than five to ten minutes.
  3. We take out, cool.
  4. Remove the remaining oil with a solution of laundry soap.
  5. Then we boil the coins again in distilled water.

During the cooking process, the noble patina may come off, therefore it is not recommended to use the method for especially valuable collections.

Electrolysis

Description. The technique is designed for professionals. There is a high risk of electric shock, therefore, be vigilant. We do not forget about eye and hand protection, so we put on glasses and gloves. The procedure is carried out in a room with good ventilation.

Procedure

  1. Cut off the plug from the power supply (6-12 W) and divide the wires into two parts. We clean the ends, attach the copper conductors to the clamps.
  2. Pour a saline solution into a plastic container: take one tablespoon of salt per liter of water.
  3. We connect the power supply to the network. We lower the metal clamps into the liquid. A hiss will be heard from one of the clamps - and we attach it to the coin. We connect the second with any object made of metal.
  4. Depending on how dirty the product is, it can take anywhere from ten minutes to several hours.
  5. We disconnect the device from the mains, take out the clamps.
  6. We clean the coins in soapy water, rinse them.

Novice numismatists should remember that the use of folk remedies will not return valuable items made of silver, copper, bronze, cupronickel silver to their original appearance. Therefore, it is necessary to prevent the appearance of patina of different colors, observing the rules for keeping the collection. We store coins in special organizers, do not take items with our bare hands. Already these two points guarantee that the need to clean coins at home will be much less frequent.

In the period from 1931 to about the sixties of the last century, coins were made from a copper-nickel alloy. Over time, such products are covered with a film of oxidation, which turns from red to dark brown. Cleaning nickel coins will not help to restore them to their original pristine appearance, since it always damages the surface to a certain extent, but it may well make them presentable.

Cleaning copper and nickel coins at home is quite possible. For each of the methods, follow some rules:

  1. Before the procedure, the products must be cleaned.
  2. During this process, do not allow skin or body parts to come into direct contact with corrosive substances.
  3. At the end of the procedure, wash the coins with soap and hot water.

The simplest way is associated with the use of soap, which is obligatory in every home. It is not difficult to dissolve the soap solution; products are dropped into it. The alkaline medium destroys the oxide on the surface, then it is removed with a stiff brush under running hot water.

The disadvantage of this method is the low efficiency of the solution. It can take a long time to achieve the desired result.

Electrolysis is not for everyone

Another way to clean the USSR copper-nickel coins would require a power source, which could even be a phone charger. The coin must be attached to the cathode (minus), the source must deliver up to 12 watts. A solution with salt (one tbsp. Spoon) or soda (two tbsp. Spoons) is brought into, into which the part is lowered. The current is applied from several minutes to an hour, depending on the desired result and the degree of oxidation of the product.

It is important to know that this method should not be applied to coins that have noticeable surface damage. The result is accompanied not only by getting rid of the oxide, but also by the manifestation of all cavities and flaws.

With vinegar and salt

A simple cleaning with vinegar damages the coin, forming imperfections on the surface, while not completely removing the oxide from the product. If you add a seven percent solution of vinegar and a teaspoon of salt to fifty grams, the result of the procedure will improve. The salt should not be stirred until it is completely dissolved: it is important to leave a small layer at the bottom. They put a coin on it and turn it over at intervals of several minutes. The procedure usually takes up to twenty minutes. After cleaning, however, a pinkish tint may remain on the coin.

In hydrochloric acid hcl

The method cannot be implemented from start to finish at home. It is almost impossible to get hydrochloric acid in stores, it comes across in rare cases in a pharmacy. It is extremely unsafe to create a substance outside of laboratory conditions. Various hydrochloric acid cleaners can come to the rescue, for example, Cilit Bang, Dressing Duck, SARMA and others.

Trilon-B for uniform oxidation

Trilon-B belongs to strong cleaning agents. In some cases, the product will damage the material, but there is nothing to worry about with copper-nickel coins. It is best to choose this cleaning method for cases of uniform oxidation coverage.

The substance can be dissolved in water in a ratio of one to ten. The solution effectively cleans the coin: the duration of the procedure depends on the degree of soiling and the desired result. After cleaning, wash the coin with soap and hot water.

GOI paste

The method significantly damages the surface of products, like any cleaning with abrasives. If the coins are rare and are cleaned for the sake of sale, cleaning with GOI paste is excluded: a thin layer of the surface is removed by polishing, small parts are erased and the items lose their value.

GOI paste is usually applied to a soft cloth, sometimes moistened with gasoline. Before starting polishing, it is necessary to wipe the paste layer on an unnecessary surface or object so that large pieces come apart and do not scratch the part.

In general, there are plenty of ways to clean nickel coins at home. Depending on the degree of soiling, you can choose a suitable one.

One of the most frequent finds on the hunt is Soviet small things in denominations of 10, 15, 20 kopecks, made of a special alloy of copper and nickel. These pennies are reddish in color, but originally they were white and shiny like silver. But, since there is copper among the components of cupronickel, it is she who is "responsible" for the appearance of red plaque. If you're wondering how to get your coin back to its original appearance, here's a cleaning method.

He came to us from cooking. In Soviet times, there were many tea spoons and ladles made of cupronickel. They tended to darken, acquire a brownish tint. And each housewife had a note on how to save her kitchen utensils from such a misfortune.

Actually, the recipe itself.

What do you need for cleaning?

You will need: baking soda, foil, boiling water (fresh from the teapot). Well, in fact, the coins themselves - 10, 15, 20 kopecks of 1931-34, which are either kept in your "bins of the motherland", or have recently been found on the hunt. Note that specimens taken out of the ground most often look frankly bad, they are in disgusting preservation.

Coin before cleaning

Cleaning process

We take a small enameled container. We put the foil. We fill its surface with soda in an even layer of two or three millimeters. Then we lay out the coins on the soda.

We also cover them with soda in the same layer as the first. Cooking boiling water: if the kettle is electric, and the water boiled about 10 minutes ago, turn it on again. Fill everything prepared with boiling water.

Close all this with a lid and leave it safely for 12 hours.

After the expiration, we take the coins out of the solution, wash them, clean them with a toothbrush. You can use soap, toothpaste, dishwashing detergent - whatever you want.

Coin after the first cleaning.

The procedure has to be repeated up to two to three times in order for most of the red plaque to go away.

Note that after cleaning the coins will immediately show damage. Where the surface remains smooth, there will be a silvery sheen, and where there are chips and scratches, the surface will remain dull, darkish and matte.

Cleaning the copper-nickel coins of the USSR (they are also cupronickel) is a constant headache for those who collect them, especially treasure hunters often face this problem. Even experienced collectors with experience sometimes do not really know how to clean such a coin in order to return it to its presentation. The fact is that this alloy is practically impossible to clean, if we talk about a good, high-quality result. Nevertheless, it is possible to improve the appearance of copper-nickel alloy coins, we will consider some relatively safe methods of cleaning and its rules with the caveat that in some cases it is better to leave everything as it is.

What are these coins?

An alloy of copper and nickel or cupronickel for minting banknotes was used on the territory of the USSR in a short period of 1931-1935. It was small things of the middle segment - 10, 15, 20 kopecks. Minting was carried out in the northern capital in exchange for silver change money. Such a metal was valued for its high wear resistance, at first it had a shiny white color, similar to silver.

But the appearance of such coins changed rapidly, they acquired a characteristic reddish coating due to copper, gradually darkened and eventually became almost brown. It is in this form that treasure hunters most often find them, and even at home the long-lying Soviet trifle of the 30s looks far from exemplary. And since these coins are of certain interest to collectors, the issue of cleaning them does not lose its relevance.

It is interesting. A copper-nickel alloy with a more noble name cupronickel came to the coin business from cooking. During the Soviet period, in many houses one could see cutlery, salt shakers and other household kitchen items from cupronickel. And, by the way, every housewife knew how to clean them.

What not to do

Before talking about how to clean copper-nickel coins, it is worth talking about how you should not do this, that is, about the methods that are useless or unsafe. First of all, you don't even need to try using soapy water, a popular method for cleaning other coin metals. In this case, we are talking about oxides, which cannot be removed by any soap. Next, vinegar should be mentioned, since they really manage to dissolve the oxides of this alloy.

But the downside of such a procedure can be very sad, the image of a coin can lose its clarity. And the alloy itself, under the influence of vinegar, tends to acquire a strange uncharacteristic pinkish color, which does not raise the value of the coin in any way, and, moreover, can translate it into the category of unusable from a collection point of view.

Hydrochloric acid

It is known from the course of chemistry that hydrochloric acid is an effective means for dissolving oxides. You should not be intimidated by this name, analogues of hydrochloric acid are used in households, in particular, for cleaning toilets (“Toilet duck”). You can use this remedy by dipping a coin into it, but it is important to maintain the correct time.

If she lies in the "duck" for several hours, the same unpleasant and uncharacteristic pink tint, for which copper is responsible, may appear on the metal. It is important to correctly assess the initial appearance of the coin. If it is not badly damaged and has the same silvery-white color, such cleaning can only ruin everything. And, as is the case with table vinegar, acid can "eat" the reliefs, which is completely undesirable.

GOI paste is another tool that is suitable only for inexpensive and not very valuable coins in terms of rarity. If you have a real rarity in your hands, this method cannot be used. Abrasive particles of the composition will erase not only the patina, but also spoil the relief, its clarity and even small details. In addition, GOI paste tends to impart an unnatural shine to metals, which is not at all typical for metal money, which were stamped almost a century ago.

How to clean copper-nickel coins?

Let's consider the main available methods for cleaning copper-nickel coins of the USSR and their features. It is highly recommended to start testing them on the lowest-value specimens, which, in case of failure, will not be a pity.

Electrolysis

The essence of the technique lies in placing the metal in a weak (isotonic) salt solution, into which a small electric current is supplied. However, this is still far from a harmless and unsafe way for humans, since you have to deal with liquid and electricity at the same time. It is imperative to provide protection for hands and eyes. For cleaning, a 12 volt power supply is taken, which requires preliminary preparation. It is necessary to cut off the plugs and divide the wires into 2 parts, stripping their ends from the insulating material. After that, you need to twist the copper wires and solder them to the metal clamps, which should not touch!

Now you need to make the electrolyte. The solution is made at the rate of 1 tbsp. l. table salt per 0.5 liters of water. It needs to be poured into a plastic container. After switching on the power supply, both clamps are immersed in water with all the necessary precautions. The one that starts to emit a hiss in the electrolyte is positive (“+” sign), you need to attach a coin to it.

The negative end of the power supply must be attached to another metal object, such as a regular spoon. In this position, the entire turned on structure can be left for a long time, up to 4 hours. The approximate time is calculated depending on the condition of the coin, how dirty it is. After that, the current is turned off, the coin disk is taken out of the liquid and washed in warm soapy water, and then wiped dry with a soft, clean cloth.

"Tilon-B"

It is an effective remedy that can dissolve patina, but getting it right is essential. For 1 part of "Trilon-B" you need to take 10 parts of water. You don't need to make a lot of solution, there is enough volume to immerse a coin there. After immersion, you need to stand nearby and monitor the cleansing process. The duration of the procedure depends on its condition. After that, the coin must be washed with soapy water, easily and without pressure, cleaning it with a soft brush. Rinse and wipe dry.

Cigarette ash

The method is more likely related to folk, non-standard, but sometimes it turns out to be very effective. You will need ash from smoked cigarettes and plain water. The contaminated coin is first moistened with water, after which ash is applied to it. She remains in this position for about 20 minutes. After that, you need to gently and carefully rub the ash into the metal, and then rinse with warm water and wipe dry.

Ayran

The well-known fermented milk drink can also help in cleaning copper-nickel coins. But this process will not be quick and gradual. A coin is placed in ayran for 3-5 days, after which it is removed, rubbed with fingers and placed in a new composition. Each time, the result is evaluated to understand how many cycles need to be applied to the desired effect. This is one method that has the advantage of avoiding reddening of the copper surface.

Soda cleaning

Let's make a reservation right away that for coins that, due to storage conditions (for example, buried in the ground), have a frankly bad look, this method is unlikely to be effective. You will need: baking soda (carbonade), foil, an enamel bowl and boiling water.

Soda is poured onto the foil in an even layer of about 2-3 mm, and a coin (or several) is placed on it. The same layer of soda is poured on top. Now you need to pour everything with a small amount of boiling (not boiled a minute ago, but boiling) water. The container is closed with a lid and left for 0.5 days. Depending on the neglect of the coin and the result obtained, you can repeat the cleaning several times. After that, everything is normal - we take it out, wash it with soap (it is good to use toothpaste instead of soap), dry it or wipe it dry.

You should be prepared for the fact that in places where the surface is damaged, it will not be shiny silver, but darker and dull.

And yet vinegar

The vinegar method, for all its "barbaric" essence, is still effective, and in some cases the only possible one. But it should be understood that everyone uses all the proposed methods at their own peril and risk. The essence of the method point by point:

  • Buy a brass brush or sponge.
  • Take a small non-metallic container and pour an acetic solution into it, based on the proportion of 1 part undiluted acetic acid to 10 parts of water. Sufficient liquid depth is 5 mm.
  • Put a coin in the solution and every 12 hours remove it from there and use a brush to remove all peeling oxides from both sides and the edge. Repeat as many times as the state of the instance requires (usually 3-10 cycles).
  • Wipe the coin with alcohol and put it to dry in a warm, bright place for several days.

After lying down, the coin will begin to turn gray and lose its luster, this is a natural process. As for scratches, they will not be visually noticeable, since the brush is still soft. But when viewed under magnification, they will of course be visible. If the oxides have "eaten" part of the metal, then after they are removed, the surface will be unsightly and uneven, like the lunar surface - nothing can be done about this, because patina is not a plaque, but a part of the metal. With poor-quality drying, rainbow stains may appear on the surface after a few months. And one more important detail: the vinegar must be of high quality and comply with GOST.

And finally, it must be said that not all copper-nickel coins covered with patina (oxides) need to be cleaned. If the surface of the coin disc is covered with a thin and even, so-called noble or cabinet patina, you should not remove it. This is an indicator of the age and authenticity of the collector's item.