How to put cabinet patina on silver coins. Available ways to self-patina on coins after cleaning

The conservation of coins is no different from the conservation of any items made of copper and its alloys. Although such finds belong to the "mass archaeological material", but this does not give a reason to treat them haphazardly.

What is hidden under the word "conservation"? Conservation measures ensure the preservation of the material presence of the monument and prevent further loss of the original. Conservation aims only at preserving the pure substance, while not paying attention to aesthetic improvements. Many people think that preserving coins is just coating. This is far from true. Conservation includes various conservation works carried out directly at the facility. For example, clearing and fixing the original surface, as well as preventive conservation measures. For example, optimization of climatic conditions, proper packaging, presentation and storage.

Before talking about conservation measures, I would like to once again recall such a concept as the original surface. There is no such term in numismatics and general practice, but there is a concept - patina. Unfortunately, this is too general a definition of an oxide film, often not giving any idea of ​​the condition of the coin, and hence the choice of the correct conservation methods. Although it is customary to divide the patina into "noble" and "not noble", but often this statement leads to the fact that the preserved original surface and its details are removed, guided by outdated aesthetic concepts.

What is the original surface? The original metal surface of the coin is replaced by metal salts during corrosion. Due to the fact that this transformation is very slow, such a layer conveys the nuances of the original surface. But, unfortunately, corrosion products and soil particles often cover relief details and distort the shape. The original surface is not only the bearer of the relief, but also gives us a good guide when clearing the coin. This is a kind of border beyond which we cannot step (except in rare cases). Everything above the original surface can be called pollution, everything below is the original.

The picture shows a section of a coin made using an electron microscope. The boundary between the original surface and deposits (pollution) on the surface is well traced. Under the original surface is a layer consisting of corrosion products.

Quite a lot of time passes before the coin hits the restorer's table. In this interval, badly preserved coins can suffer significant irreversible damage. There are mainly several factors involved, one of which is improper handling of the unstable patina.

In general terms, the following can be said on this topic:

1. After removing the coin from the soil - do not rub or try to clean the find in order to see it better. Findings must be handled with the utmost care.

2. Try to immediately determine the condition of the patina and in case of damage (porous structure, cracks and chips, bumps and growths, missing surface fragments, etc.) in a dense layer of patina, be sure to wrap the object in a damp cloth moistened with distilled water (or just wet earth) and put in a tightly closed box. In this way, we prevent the patina from drying out. In addition, the risk of physical damage to the patina caused by vibration and shock is minimized.

3. Try to keep the time between the extraction of the find and the start of the desalting (washing) to a minimum. For a long time, the find should not be in a wet wipe, otherwise there is a risk of subsequent corrosion. In particular, this applies to objects that have active foci of bronze disease.

4. Pre-clear (flush) only if the patina is stable.

5. For all finds with a damaged patina (whether it peels off or not), a salt washing process is mandatory. But it must be taken into account that prolonged washing negatively affects the state of the patina. Important: optimally determine the flushing time. Usually, for finds with a thin layer of patina, this period does not exceed two days. If the condition of the patina allows, it is recommended to remove loose dirt with a soft brush and distilled water. If there is a possibility of patina flaking, then there can be no talk of any preliminary clearing.

I want to stop on washing with distilled water. The purpose of washing is not to soften oxides and soil residues, but to remove soluble salts that are in the capillary system of the patina. Any plastic box with a tight-fitting lid will do. The cover not only prevents water evaporation, but also prevents gases and salts from entering the air. The container must be completely filled with water, otherwise there is a risk of harmful substances from the air gap. The coins should be kept as close to the surface of the water as possible. You can use a plastic strainer for this. In the course of desalination, it is necessary to turn the coins at least once, so the process of salts coming out from the underside of the coin goes much faster. This should be done not with your hands, but with tweezers. You can't put your fingers in the water.

:!: Important: Do not underestimate the destructive power of distilled water. Distilled water is the best solvent for salts, including those that make up the patina. Excessive exposure of coins to distilled water can lead to irreversible damage. :!:

How much exactly the coins should be in the wash can only be determined empirically, by measuring the concentration of salts with a solimeter or by determining their quantity and quality in other ways. As a rule, the layer of impurities, including oxides, on the surface of a coin does not exceed a few millimeters. In this regard, the process of salt release is relatively fast and takes from 24 hours to several days.

To improve the result, at the end of the washing period, it is necessary to take out a coin with tweezers and wrap it in a wet cloth moistened with distilled water (clean, without additives of perfumes or oils). Lightly press the soaked pulp against the coin with a brush, so that it is in full contact with the surface. You can also use toilet paper, but not bleached with chlorine. After that, it is necessary to place the coins wrapped in cellulose on a wire rack in a dry place. It is necessary to wait until the surface of the compress is completely dry and only then carefully remove it. When dried, salts migrate from the capillary system into the compress material.

Salt washing is mandatory for all coins, except for those that have a dense, undamaged patina.

Findings with a noble patina can be simply rinsed with distilled water.

Determining the safety of coins

Ideally, the metal surface of the coin, or the entire coin, will be converted into a mineral by corrosion, while the shape of the object does not change. There is only a substitution of one material for another. Thus, the surface of a copper coin is replaced by a new one, for example, a malachite surface. The formation of such a patina can be called pseudomorphosis. The appearance of a noble patina directly depends on the environment.

Depending on the mineral formed, the surface color of the coin can vary greatly.

Here are some examples of this patina:

Patina, which has an even, uniform color, is most preferred by collectors. But, not all coins have such an original surface. In many cases, the process of converting a metal into a particular mineral does not occur evenly. In this regard, the coin acquires a non-uniform hue. Such a patina at first glance does not look very aesthetically pleasing, but it is she who is the source of information, namely the carrier of the relief.

Pollution and loss

If we talk about the state of the coin, then we can distinguish two main sub-items. Namely, pollution hiding the relief (original surface) and losses. As already mentioned, everything that is on top of the original surface can be attributed to pollution. But not infrequently, pollution itself is a source of information. So, for example, in the corrosion products deposited on the surface, you can find the remains of organic materials, whether it be old vegetation or the remains of a purse. In addition, pollution can tell us about the conditions in which the coin was in the ground, how polluted the atmosphere was at one time or another, what fertilizers were used in this area, or where this coin was found in general, as well as provide answers to many others. questions.

Speaking of pollution, two types should be noted here: stratifications formed during the corrosion process and soil stratifications. As a rule, both types of pollution are present at the same time.

Here are some examples:

In some cases, contamination covers the entire surface of the coin with a thick crust, and it becomes completely impossible to determine the denomination, read the inscriptions or the date. But still, under the layers of corrosion products and soil layers, there is always an original surface bearing numerous relief details.

The photographs below clearly show that the original surface can be found under a layer of dirt. The only question is how to properly clean such a surface and reveal all the preserved details, but we will return to this later.

Destruction and loss

The loss of the original surface can be attributed to irreversible destruction, which is practically impossible to restore. In this case, there is a loss of part or all of the relief of the coin. The destruction of the patina can occur as a result of mechanical damage, chemical exposure, as a result of changes in external conditions, temperature changes, humidity (when the processes of recrystallization of copper salts in the corrosion layer can begin) or washing out of unformed layers with water. This also includes the destruction caused by improper handling of unstable patina.

Several examples of coins whose relief has been almost completely lost

Ten pfennigs 1912. The original surface has been preserved in fragments. Under a layer of dark patina is a bright red loose layer of cuprite. The thickness of this layer is relatively large.

General view of the coin.

Reverse side of the coin. Losses.

Often, after cleaning, the coin looks really bad, I would even say not really bad. This is mainly due to the fact that the so-called patina was destroyed and the coin remained in the negligee. Selling such a coin is very problematic. It is necessary to prepare it a little for sale (like a car), i.e. apply patina.

Patination of copper coins, in principle, is not very difficult. The main difficulty is that the acquired color resembles natural as much as possible. There are many ways to patinate copper coins, each has its pros and cons. I only use three methods. I'll tell you a little about them.

Patination of copper coins with manganese and copper sulfate. Many numismatists consider this method to be the most “ideal”, since the color of the coin can be made from red to dark brown, and this induced patina will be very similar to natural. Patination occurs as follows - in water heated to 90 degrees (0.5 liters), add 3-4 grams of manganese and about 10 grams of copper sulfate. Mix everything and place coins in this solution. Warm the solution slightly as it cools. Turn the coins every 5 minutes and check their color. Achieve the color to become bright brown. A big plus of this patination is that the color is beautiful and relatively resistant to washing off.

Patination of copper coins with sulfuric ointment. "Real" numismatists despise this method, which is quite simple. Take a coin and smear it lightly with your fingers with sulfuric ointment. All this should be done in barely warm water. Water is needed so that the staining process is slower. At the output, the color of the coin will be from dark brown to matte black. The advantage is that the most dead coin can be revived a little, and the disadvantage is that the color is unnatural and the patina is very easily washed off. In order to make the patina natural, after patination with sulfuric ointment, the coin must be rubbed with a soft cloth dipped in oil. Sometimes you can achieve a very good color.

I really like to patinate copper coins in a natural way, i.e. sun and air. He conducted such an experiment - he put the coins, cleaned to the very "nudity", on the roof of the house. I turned over the coins every two weeks. For four months the coins were burned by the sun and washed by the rain. The result was normal - the color from bright red to dull brown. If the coins had lain in the open air for at least 7-8 months, then they would have become ideal. I highly recommend this method for those who are not in a hurry. The result will be amazing.

About 2600 and a half years ago, the first coins began to appear. Their material, variety and value have changed dramatically since then. Today, any rare coin gives the impression of something unique, and among them there are rare specimens.

For example, coins used in circulation on one island, which weighed up to five tons. These works of numismatics were made in the form of a plate. Such an amazing form of coins had a lot of advantages. The number of stones around the hut spoke of how rich the inhabitant of the island was, as well as a clear advantage - the weight of the coin, because it was not possible to carry it away.

In China, the role of cash payments was assigned to metal plates weighing up to 4 kg. The number of coins on them reached hundreds. It was easy to calculate, but it was impossible to lose a coin. Two parts made up the Australian dollar: the part that was in the center was removed. Each part of the dollar had its own denomination.

Interesting
The object of attention for collectors is not only old coins, investment and commemorative coins deservedly occupy their places among unique coins.

Due to the high price, many copies are a good economic investment. Today, the technology of production itself, style, aesthetic value and circulation of produced units have the greatest influence on the price of collectible items.

Coins are made from a variety of metals and come in a variety of shapes. Their weight can reach several kilograms, and the color scheme knows no boundaries.

Royal coins

The tradition of producing coins with the image of the king in Russia was introduced by Peter l. His profile was depicted on large coins. This law was repealed by Emperor Paul l. It is known that he did not differ in attractive appearance. He introduced a ban on the image of his face on money and this tradition was forgotten for almost a hundred years.

Alexander lll became emperor in 1881, issuing coins with the head of state again became a hot topic. But his face was allowed to be depicted only on money, with a large denomination. Because it was not allowed that significant money fell into the hands of the poor.

Nicholas II, during his reign, completely renewed this tradition. The coronation ruble was issued in 1896. This coin has been passed down as a relic for generations. The cost of these numismatic products is about 24 thousand rubles, and if the product is in good condition, then the price reaches 114 thousand rubles.

Ruble of 1898 - known for the fact that the relic is made of silver. The issue of the coin was dedicated to the opening of the monument to Alexander ll. The price is 228 thousand rubles, but the cost of certain copies reaches 685 thousand rubles.

Commemorative ruble of 1912 - the price of such a coin is up to 85 thousand rubles.

The Gangut ruble is the last numismatic commemorative relic from the time of Tsarist Russia. The price of copies reaches 300 thousand rubles. If the coin is real, then its value can be about 2 million rubles or more.

A rare copy of gold coins is 10 rubles of 1906. The number of coins that have survived to this day is only 10 units, which is why the price is very high - about 1.4 million rubles.

Coins of the USSR

Of particular value among the coins of the USSR are coins of 5 kopecks, 10 kopecks and 15 and 20 kopecks of 1931, 1934 and 1958. The price of many copies reaches 100 thousand rubles. In the market, the price of these products tends to skyrocket. That is why these unique cash settlements from the times of the USSR are a good way to invest.

The coin "George the Victorious" is the first coin of the USSR used for investments. The first circulation was 751 thousand copies. Unfortunately, this numismatic unit has failed in the Western market.

Patina on coins

Patina is a film or plaque on copper that forms on its alloys. It is a multi-layered structure, but, as a rule, the top layer of green-colored copper carbonate is considered to be the patina. There are two types of patina: artificial and natural.

Interesting
The appearance of a natural patina usually takes several months, waiting long enough. Then it is customary to use artificial patting.

Patination of copper coins

1. For this method, you need to use 5 grams of manganese and 20 grams of copper sulfate. We dissolve two elements in 1 liter of water. Then this solution is brought to a temperature of 90 degrees. With sufficient heating of the solution, we place coins in it. There is no specific time limit for holding coins.

2. The second method is carried out using a substance such as sulfuric ointment. It should be applied to coins and left for 5 minutes. It is better to smear the coin under water, as the reaction is almost instantaneous. When a brown color becomes noticeable, the coin must be cleaned and rinsed well with water. This is done so that the coin does not turn black. However, even so, one should not exclude the possibility that it will turn black. To restore the brown tint to a coin, wipe it with a piece of cloth soaked in a fat-based liquid.

3. The third method is characterized by the use of sodium hyposulfite. A prerequisite is a dry surface of the coin. It is necessary that she stay in a heated solution of sodium hyposulfite. After the coin dries, you need to wipe it with a soft cloth. Thanks to this, the coin becomes a bronze hue, and it is not afraid of corrosion.

Patination of silver coins

Patination silver coins suggests the presence of ammonia and ammonia. We put the coin in the freezer compartment for half an hour. We bring the coin to a container with ammonia or ammonia. The coin will begin to acquire a gray patina instantly.

As described earlier, Patination of coins depends on the material from which they are made, so you should carefully study and then choose the method of artificial aging of the coin that is most suitable for your coin.

The word "patina" comes from the Italian language and means a film on any surface, formed under the influence of the environment. Thus, patina can be on both metal and objects made of any other material (even stone). Usually it allows you to judge the authenticity of an ancient object, antiques. This article discusses the patina on coins, which can be of several types.

Coin with cabinet patina

Even a properly stored coin is never completely protected from metal oxidation. But if there is no (or maximum limited) exposure to air, and the storage material does not have aggressive properties, then the layer of oxides will lay down neatly and slowly. This patina is called "noble" or "cabinet". The second concept is used among Russian collectors and came from past centuries, when collections were kept in münzkabinets - special wooden cabinets with retractable trays. Wood, velvet and lacquer acted on the metal, resulting in a beautiful, but rather thick patina. In other countries, the term "cabinet wear" is sometimes used, meaning coins that were not in circulation, but were stored in the wrong way. Indeed, the choice of finishes for the münzcabinet did not depend on the desire to secure the coins, but on the desire to create a beautiful shell for the collection.

If the coin has lain in the ground, or in the air, and perhaps even under water or in some other unfavorable environment, then it also receives a patina, but such a patina is likely to be ugly. In this case, the term "metal oxidation" is used. Oxides can attack the metal so strongly that they cause gouges that become visible after cleaning. It is better to remove oxide stains in time, otherwise the coin may deteriorate. In some hoards, even coins with completely disappeared metal (crystallized) are found, that is, only patina remains in the form of a coin.

The task of the collector is to ensure that the coins are stored in such a way that a good attractive patina will form, indicating the age of the item and protecting it from further environmental influences. The absence of a patina will not decorate an old coin, rather it will cast doubt on its authenticity, therefore it is strongly not recommended to intentionally wash off the patina. Dirt that has clogged into hard-to-reach places should not be mistaken for patina. A real patina also covers a part of the field of the coin without a pattern, and not just the recesses.

Types of natural patina

Noble patina on a coin from circulation

The type and color of the patina depends not only on the storage conditions and metal, but even on the impurities that make up the coin. For example, even a small amount of iron can lead to a reddish tint. Usually it is the oxidation of impurities that leads to the formation of patina on precious metals. For example, gold is generally not subject to noticeable oxidation, but its sample is almost always not the highest, which means that it contains a certain percentage of other metals.

Orange to brown dots or streaks can form on gold coins, this is the result of the oxidation of copper, the main component in high-quality alloys (pure gold). The presence of streaks of patina (rather than stripes or dots) indicates that it is most likely artificial.

Black patina on silver

Silver is first covered with a yellowish patina, then crimson, then blue-green, and eventually a black or dark gray patina appears. All this is the result of interaction with sulfur in its various manifestations.

Most patina options are found on copper coins. Copper oxide forms a brown or black color, sulfates and sulfides give a green color. Greenish friable streaks (“bronze disease”) are the result of the appearance of copper chloride, which very quickly leads to damage to the metal. When removing such stains, notches are formed. The most beautiful patina on copper is "malachite", formed by the action of carbon dioxide from contact with air. On the surface of the coin, a thin layer of malachite crystals is formed, which has a blue-green color.

Oxides that caused damage to the coin

Modern coins made of copper-nickel alloys or stainless steel are slightly susceptible to plaque formation, the color can vary from gray to golden. Aluminum tarnishes over time and becomes covered with a grayish coating. Brass coins, upon contact with air, darken after a few months; with proper storage, this process slows down significantly. Some specimens may lose color and become almost white, while others turn brown. The reddish color of brass indicates exposure to chemicals.

IN Lately In Russia, more and more non-ferrous metal coated steel coins are being produced. In the case of the presence of the smallest, even imperceptible hole, the steel comes into contact with air or a humid environment, it rusts, and the coating swells. Such coins are unlikely to ever boast of a “noble” patina.

Types of patina on old coins:

Bullet patina. A beautiful fine coating as a result of careful storage, changing from almost imperceptible in the center to rather dark around the circumference. Often individual areas have a darker color. This type of patina greatly decorates the coin and gives it value.

Rainbow patina. It is a plaque that has slightly different colors in different parts of the coin. In general, the colors should be similar, and transition smoothly, without sudden changes. This is usually due to non-uniform mixing of the alloy metals, especially on old coins. Production technologies of two hundred years ago did not always make it possible to achieve metal uniformity, this helps to distinguish originals from fakes.

Iridescent patina. An even coating that changes color as the viewing angle changes.

Coin with pantry patina

It is formed naturally when a coin is found underground for a long time in a closed container. A very thick brown coating appears on copper coins, after which recesses can form after removal. On silver coins, as a rule, "horn silver" - raised spots appear due to contact with chlorides contained in the soil.

Sand patina. Formed on copper coins that have lain in the sand for a long time. It has an even yellowish-beige color.

artificial patina

Copy of a rare coin

The value of patina for old coins leads to its artificial induction. This may be necessary in case of cleaning, if the coin has acquired an unnatural shine or color for its age. In addition, with the help of artificial patina, they can hide defects (scratches, potholes, dents, "metal bloom"). Aging can also be used in the manufacture of copies of rare coins; in almost all cases, they are easily recognized by small details, even in the presence of a beautiful artificial plaque.

Coloring. The most unprofessional method, used in the manufacture of cheap copies of coins. It can be distinguished by its luster (real patina does not shine) or by a noticeable thick layer of dark substance. Such a patina abruptly breaks off, and does not fade smoothly towards the center. Even such a method of aging can be confusing for a beginner, but for an experienced numismatist, one glance is enough to recognize a fake.

Burning. It is also a short-sighted way, since even an inexperienced collector can distinguish a layer of burning from a patina. They use a blowtorch, heating a gas stove on an open fire, placing it in a fire, etc.

chemical methods. They are reduced to creating conditions under which the aging process is accelerated many times over. There are many ways, here are just a few:
- put 80 g of copper sulfate and 5 g of potassium permanganate per liter of distilled water, then heat the liquid strongly (but not to a boil) and place the coin for several minutes;
- rub the coin with sulfuric ointment and rinse with soap and water;
- immersion in sulfuric acid, or other sulfur solution. Sulfur has a strong effect on the metal, causing rapid oxidation. They even use sulfur stripped from matches.

folk methods. Here the fantasy is limitless, but without the development of experience, most likely, instead of aging, you will get just a damaged coin. Coins are kept for a long time in an unfavorable environment (heat, moisture, evaporation, aggressive liquids), baked inside potatoes, etc.

Definition of artificial patina:
- sharp color changes, too strong darkening to the edges or in hard-to-reach places;
- shine patina (real patina is matte and never shines);
- the appearance of colors unusual for metal (for example, the reddish color of brass) indicates a chemical effect;
- a scratch or a pothole is found under an even layer of patina;
- the presence of patina only at the highest points of the relief.

Artificial patina never increases the value of a coin, and in most cases only lowers it. A real patina has a unique tint of antiquity that can never be exactly replicated. The exception is ways to accelerate natural oxides, but this still takes years.

The article was corrected and supplemented by Admin, photos provided by site users: Andrey_P, Moneta100, 3715.

It has long been known that metals oxidize over time when exposed to atmospheric oxygen. And if iron is destroyed as a result of this, then copper is covered with a patina - an oxide-carbonate film that slows down the oxidation process. It is the patina that gives it a special charm. old coin, indirectly testifying to its authenticity. Unfortunately, during the cleaning process, along with contaminants, you have to remove natural patina. However, by patinating copper coins, you can restore them to the look of undisturbed antiquity. Often, artificial patination of coins is justified from an aesthetic point of view, as it helps to retouch the results of their cleaning.

There are many ways to patina copper coins. With any patination method, the same set of tools is basically used. It is enough to have on hand:

• a glass or plastic container for preparing solutions;
• bath for washing;
• spoon
• beaker;
• table scales;
• glass and wooden sticks;
• brush;
• degreaser;
• latex gloves;
• respirator;
• laundry soap;
• sponge
• rags;
• paper towels.

Before and after patina

The patina process

Undoubtedly, the presence of a "native" patina reliably protects the coin from damage. Ideally, it is better not to touch it at all. However, sometimes the removal of collection merits is a necessary measure for the following reasons:

• due to the onset of corrosion;
• great pollution;
• strong uneven patination layer.

In such cases, you have to resort to self-patination. In this regard, a reasonable question arises, how to apply an artificial patina to copper coin? The essence of this process is the impact on copper of chemicals and compounds.

For patination, the following methods are usually used:

• coins are dipped in a patinating solution;
• apply the solution to the surface with a brush;
• place a banknote in a vapor-gas environment.

The quality of an artificial oxide-carbonate film depends on the method of its production and on how well the base is prepared for it.

Preparing a coin for putting on a patina consists in cleaning its surface from grease and oxides. It is easier to do this with a cotton pad dipped in white spirit or gasoline. These solvents will help clean it of greasy traces that make it difficult for the patination solution to react with copper. From this point on, it is imperative to wear gloves, because the patina does not lie evenly on the left fingerprints.

Ways to build a patina

In an aqueous solution of copper sulfate and potassium permanganate. To restore a beautiful golden brown patina, it is enough to dilute two teaspoons of copper sulfate and 1/3 teaspoon of potassium permanganate, commonly referred to as potassium permanganate, in 200 g of water. Heat the solution in a water bath, but do not boil. Dip the coin briefly into the solution several times until the desired color is obtained. Upon completion of patination, the banknote should be thoroughly rinsed under the tap and dried. Matte can be easily removed with a woolen cloth.

With the help of ammonia. This method has two implementation options:

1. Pour ammonia into a small container, for example, into a cork from a plastic bottle, place it in a plastic container along with a coin that you want to age, then close it tightly and leave it for a while. The result becomes noticeable after 1-1.5 hours.
2. Fix the coin on any thin wire or thread. Place it in a glass jar with a small amount of ammonia so that it hangs over the ammonia. Remove the end of the wire from the jar, closing it with a lid. The reaction will begin very quickly, and changes will occur literally before our eyes. With the help of ammonia vapor, the desired effect will be achieved much faster than in the first version, after 10-15 minutes.

By the way! You should not resort to heating ammonia vapors, otherwise the patination result will be spoiled by the resulting condensate.

Sulfur ointment. In fact, this drug is intended for the treatment of scabies, but it is often used to induce a patina. It is worth noting that in this respect it is very effective, since it contains a lot of sulfur. Contact of copper with sulfur leads to the formation of copper sulfide. This compound quickly turns black and firmly covers the entire surface of the banknote. Therefore, to obtain a light brown patina, you need to act a little differently.

It is better to apply quite a bit of ointment on the pads of washed fingers, rubbing it over the surface with a thin layer. After that, do not touch the coin with sulfur fingers. Next, you need to pour hot water into the bath and lower the coin pre-washed in citric acid into it. Then, with sulfuric fingers, take it under water and begin to rub the ointment into its surface, without lifting it into the air. When you get the desired color, wash the coin with a brush with "Fairy" without removing it from the water. As a rule, the effect obtained exceeds all expectations. Whereas the performance of such manipulations directly in the air leads to the formation of an unattractive black patina, which, moreover, begins to fall off very quickly.

in a solution of copper oxychloride. Pour hot water into a half-liter jar. Dilute in it two tbsp. spoons of copper oxychloride (HOM). This substance is easy to find in stores selling fertilizers. The result is a saturated blue-green solution. 100 ml of ammonia should be added to it. From now on, it is better to work in a respirator so as not to smell the suffocating smell of ammonia.

A copper coin must be immersed in the prepared solution and left for 30 seconds. Then take it out and inspect. This manipulation must be repeated several times until the desired effect is obtained. In conclusion, the coin should be washed in soapy and clean water, dried and admire the beautiful brown-olive patina.

In general, if you forgot that this should not be done and washed away the natural patina, it will be quite possible to restore it.