How to restore damaged and wrinkled coins. Methods and rules for restoring coins What tools are needed for restoring ancient coins
Let us introduce you to safe ways to clean coins from an archaeological metal restorer with many years of experience in the Hermitage. An article about these cleaning methods was published in the book “The Past of Our Motherland in Numismatic Monuments.” Author useful material– Hermitage employee O.V. Vasilyeva. Let's move on to the most useful excerpts from the text.
Clearing Coins- one of the responsible types of restoration, it is important for their study, dating, identification and storage.
Ancient coins made of silver and copper alloys, discovered in treasures or other archaeological excavations, most often arrive at the restoration workshop heavily corroded, sometimes completely mineralized. Under the influence of water and salts, copper is destroyed in the soil with the formation of green carbonates and chlorides, red cuprous oxide and black oxide. In the corrosive layers on bronze coins compounds of tin and lead are found. Silver-copper alloy coins are often coated with copper corrosion products. Sometimes silver, under the influence of chloride salts, turns into gray-violet chloride, horny silver. In air, copper alloys darken due to oxidation, and silver - as a result of the formation of sulfide.
Restorers always treat the restoration of numismatic monuments with great caution. In particular, they do right choice reagent necessary for cleaning from corrosion, since a reagent successfully used for some coins may be unsuitable for others and will lead to their destruction or distortion of their appearance. It is advisable to achieve the preservation of a noble patina, a kind of certificate of antiquity of objects.
So, when starting to clean coins, you should first of all find out what metal they are made of, whether they have a metal core, to what extent it has been preserved, and what salts the coins are coated with.
Cuprous chloride
Important, for example, in corrosion crusts on copper coins ah determine the presence of copper chloride, which in humid atmospheric conditions causes an active corrosion process - “bronze disease”. To detect copper chloride, a humidification chamber is used: a glass vessel is filled with water to approximately 1/7 of the volume; A perforated plate made of plastic, plexiglass or porcelain is placed above the water, on which coins with a corrosive layer are placed. The container is tightly closed with a lid. It is left in this state for 1-3 days.
The effect of the humidification chamber is to accelerate processes occurring under the influence of air humidity, which helps to identify areas of active corrosion and makes it possible to choose more successful cleaning methods. Keeping coins in the chamber helps loosen the surface layer of oxides, facilitating further cleaning operations. If there is copper chloride in the corrosion layer, droplets of liquid, colorless or slightly greenish, appear on the surface of the coins. Otherwise, the droplets do not protrude: copper carbonate, nitrous oxide and copper oxide are stable in humid conditions (horny silver on silver coins also stable). And if copper chloride is detected, it must be removed from the deepest pores and very thoroughly.
Stuck
Often during excavations, coins are found boiled, forming a shapeless mass. We do not recommend separating such coins by heating them and immersing them in cold water. To avoid loss, such a lump should be placed in a 5-10% sodium hydroxide solution and heated to 30-50°C. After this, the coins can be separated from each other, determine the condition of each of them and begin cleaning.
Cleaning methods
The main methods of clearing coins are mechanical, chemical and electrochemical. During restoration, a combination of mechanical methods with others is practiced.
Mechanical treatment consists of removing surface layers: earth, sand and individual corrosion tubercles. It is performed using various brushes, scalpels and dental burs of various sizes. But if used roughly, it is easy to cause scratches that will distort the inscription, images, etc.
- Copper coins
Chemical methods, in combination with mechanical methods, clean coins that are covered with a thick layer of corrosion products, but have retained the metal base, as well as coins made of gold and silver.
To remove the cherry-red coating of cuprous oxide from copper coins, you should immerse the coins in a 5-15% ammonia solution, but so that they are completely immersed in the solution, because in contact with air the effect of ammonia on the metal will be destructive.
If copper coins are coated with salts consisting of copper carbonate (dark green), these deposits should be removed with a 5-10% citric acid solution. It slowly dissolves copper salts and oxides and does not dissolve metallic copper.
There are also copper coins coated with a yellowish-pale coating of lead carbonate. This suggests that the alloy of the coins themselves contains a lot of lead or they were lying in the ground with lead objects. To remove such deposits, you should use a 10% solution of acetic acid, which easily dissolves lead carbonate.
The restorer often has to deal with coins that are completely mineralized, which cannot always be preserved. The success of the treatment depends to a large extent on which compounds have replaced the metal through complex mineralization processes. First, carefully remove surface deposits. If in this way it is possible to identify this or that ornament, inscription, etc., then this should be limited. If mechanical processing does not open the coin, use a 5% solution of caustic soda or ammonium carbonate.
Attention! Since the degree of preservation of coins varies, it is difficult to give recommendations regarding the time they spend in one or another reagent. Therefore, periodically removing coins from the solution, you should gradually remove the softened layers mechanically, thereby speeding up the cleaning process.
- Silver coins
Silver coins are cleaned primarily by chemical means. Such cleaning is reduced to removing oxides and salts of other metals, mainly copper compounds, from the surface. Copper connections on silver coins are identifiable by their green color. To remove them, place the coin in a glass vessel or porcelain cup and fill it with a 5% sulfuric acid solution. To speed up the process, you can clean with a heated solution, removing the coin from time to time, rinsing it with water (preferably running water), then removing the mechanically softened salts with brushes. You can also use a 5-10% solution of formic acid, preferably heated to 50-70° - the hotter the solution, the stronger its effect.
Formations of violet-gray horny silver are exceptionally soft. Such coins often lack a metal core, and during cleaning the possibility of their complete loss cannot be ruled out. But if the horn silver crust is not too thick, the coin can be immersed in a 5-10% ammonia solution. In these solutions, the horny silver softens, after which it is carefully removed mechanically.
A brass brush is a restorer's tool.
For coins that retain a metal core but have very dense, hard, thick oxides, as well as for fragile coins, the electrochemical reduction method can be applied. This method does not require special equipment. For electrochemical processes, zinc and aluminum are usually used. Practice has shown that for cleaning coins it is best to use plates made of sheet zinc or aluminum, with holes punched in them (like a grater). Formic acid of 5-10% concentration is taken as an electrolyte. A zinc or aluminum plate is placed at the bottom of the glass vessel. Several coins are laid out on the grated surface of the plate, which are covered with the grated surface of another similar plate. After this, the vessel is filled with the prepared solution so that the coins with the plates are completely hidden.
Processing using this method should be carried out especially carefully and carefully, with frequent monitoring of the progress of the process. Mechanically removing the restored and softened corrosion products, inspect the coin through a magnifying glass to determine the degree of its cleaning.
Note that gold and new coins that have not been in the ground, but have only been in circulation for a long time, can be cleaned easily and quickly. It is necessary to remove fatty substances from them with acetone, gasoline or alcohol and dip them in a 5-10% solution of citric or formic acid.
After cleaning
After cleaning the coins in one way or another, they should be thoroughly washed (boiled) in several changes of boiling distilled water until the water reacts neutrally according to the universal indicator. After washing, the coins are dried in acetone, then in alcohol for 30-60 minutes. For this purpose, you can also use a thermostat (a special drying cabinet), keeping coins in it for no more than two hours at a temperature not exceeding 100 ° C.
If copper coins have an unpleasant shine after cleaning, you can artificially create a light to dark brown patina. To do this, you need to take 50 g of copper sulfate and 5 g of potassium permanganate per liter of distilled water. Place coins in the prepared solution, heated to 70-80°, and hold until the desired shade is obtained.
After drying, the coins must be preserved with a protective coating - paraffin or synthetic resins. For this, we can recommend 5% solutions of polybutyl methacrylate in acetone, toluene or xylene and polyvinyl butyral in alcohol or a mixture of alcohol and benzene (1: 1).
After conservation, it is necessary to store coins and medals not in piles, but in separate cells of albums or in trays with compartments.
Additional information about metal restoration can be found in the books by M. V. Farmakovsky “Conservation and Restoration of Museum Collections” and H. D. Plenderlis “Conservation of Antiquities and Works of Art.”
Well, about more modern methods of cleaning coins using effective means, read on “MDRegion” and look at our channel on YouTube.
10 rubles bimetal before and after cleaning
Many novice collectors, or those who are just looking at a new field of collecting - numismatics, dream of returning the shine to their coins. Especially if these coins are in poor condition, very old, or out of circulation. There is especially a desire to cleanse those that have some value.
If you decide to use cleaning, you must first try it on a coin of insignificant value. Moreover, it should be taken into account that different metals may react differently to cleaning methods.
What not to do
First of all, it is worth noting that you should never clean absolutely all coins to make your collection shine! They will certainly become more beautiful, but they will most likely lose their collectible value. The fact is that the condition of the coin depends not only on its purity, but to a much greater extent on the preservation of the relief. Any smoothing of parts, the formation of gouges from removing oxides, or even just the loss of slight roughness reduces the condition and, accordingly, the value.Let's consider barbaric methods cleanings that are most often used by beginners:
1. Mechanical cleaning by friction with a rag, carpet, etc. (in common parlance – “cleaning with felt boots”). Sometimes GOI paste (green, like plasticine) can be used, but it only worsens the damage to the coin. GOI paste can only be used for certain types of jewelry (not antique), where shine is of paramount importance. In general, its main purpose is to clean optical lenses.
2. Rough dry cleaning with acids and other aggressive compounds. In addition to removing dirt and oxides, part of the surface disappears, and bumps and dents form. Any acids must be diluted with water (preferably distilled) in a ratio of at least 1/7.
3. Scratching a coin with metal or other objects in order to remove a layer of dirt. In this case, the surface deteriorates irrevocably, scratches and gouges appear. The method can only be used to remove adhered dirt, and only with a wooden object (for example, a toothpick). If the coin is not valuable, you can use a toothbrush, but be extremely careful.
Preparing to Clean Coins
Museum restorers have a rule that can be applied to coins: the process must be reversible. That is, it is necessary to remove only late layers without affecting the original surface. Guided by this rule in most cases better coin Do not clean it, but leave it as is. But if the coin looks really bad, then cleaning should be done.For modern and Soviet coins Cleaning should be used if clearly visible stains appear on them, images are poorly visible, or there is dirt. For coins of imperial times and earlier, cleaning is used only in the case of large layers of oxides that distort appearance, or threatening the coin. An even patina (noble) indicates its authenticity and centuries-old history, and a shiny coin from this time looks like a fake. Patina is also an additional protective shell that prevents exposure environment. Bringing back patina is a complex process that requires a lot of experience.
For very old coins, for example ancient Russian ones, which are in very poor condition, the presence of a metal core should be taken into account. That is, the coin could be so oxidized that the metal itself completely disappeared, leaving only a crust of oxides. By removing this crust the coin will be lost.
In addition to determining the metal, it is necessary to take into account the nature of the oxides. When interacting with reagents, elements in the layer can damage the coin. The rind of copper coins may contain copper chloride, which appears as green spots or a flat greenish color. Cuprous oxide has a reddish tint, and lead carbonate gives a light yellow tint. All of this must be removed to avoid further destruction, but each has its own method.
Silver coins most often have blackness in hard-to-reach places, which is better not to touch, it does not pose any threat, and at the same time gives the silver a noble antique look. Gold rarely oxidizes, only as a result of a very aggressive environment. So-called “flowers” can form on noble metals - point stains that are very difficult to remove. This is the result of oxidation of impurities, unless the alloy fineness is very high.
If the coins have not been cleaned at all, then before placing them in the collection, it is advisable to carefully (without rubbing!) wash them in soap and water, rinse and immediately wipe dry. Drying under a lamp is allowed, but if you use hard water, a residue may remain in this case. Sometimes simply wiping off fingerprints with a damp cloth is enough to prevent them from etching into the surface (this only applies to new coins and coins in excellent condition).
Cleaning collectible coins of improved mintage (proof, BU, UNC) is highly not recommended, otherwise the surface can be easily damaged. It is better not to touch such coins at all and immediately place them in plastic capsules. For them, if cleaning is applicable, it is a very light chemical cleaning without any mechanical impact.
Proper Cleaning Methods
Cleaning copper coins:
Removing cuprous oxide (reddish deposits). Immerse the coins (completely, otherwise the metal may be damaged) for several minutes in a 5-10% solution of ammonia or ammonium carbonate. Ammonia will also work. All these substances have a very pungent odor; you need to work more carefully.
Removing copper chloride (green deposits or stains). A solution of citric acid or lemon juice is best. Leave it on for several hours until plaque removal begins, then rinse.
After cleaning, check for the presence of tiny chloride particles. To do this, you need to take a container filled 1/3 with water and cover it with a plate with holes. Place coins on top of the plate and keep for up to 3 days. If droplets of liquid appear on the coins, cleaning must be repeated.
Removing lead carbonate deposits (yellowish tint). Table vinegar or 9% acetic acid solution should be used. Such a deposit is rare, usually when coins are found next to lead products.
Cleaning coins made of various metals:
Electrolysis cleaning. Suitable for very heavily soiled or oxidized coins. It should be used in case of loss of distinguishable images, but it is important to remember that after cleaning, indentations may remain from the presence of oxides there, and the coin will no longer become new. If the coin has crystallized and no longer has a metal base, then it cannot be cleaned.
The electrolysis method looks like this: a glass vessel (to better see the process) is filled with electrolyte (conductive liquid), the ends of low voltage wires (preferably 9-12 volts) with crocodiles are lowered into the jar, a metal object is placed on one (with a minus sign) crocodile (for example, a nail), and on the second with a plus sign (+) a coin is attached. If you mix up the terminals, then the coin, on the contrary, will begin to absorb particles of the nail. The electrolyte can be a weak saline solution (a teaspoon per glass) or a citric acid solution. Correct connection will result in bubbles on the coin (not on the nail). You can only keep a coin in such a bath for a few minutes.
Electrolysis process in fragments and result
Ultrasonic bath. Invention recent years, sold in numismatic stores. It works on the principle of microscopic vibration that destroys plaque. As a rule, it does not spoil coins, but the result is not always achieved.
Separating stuck coins. Coins from ancient treasures may be stuck together due to the accretion of oxides among themselves. Under no circumstances should such a lump be broken or crushed so as not to destroy the coins. The lump is placed in a 5-10% sodium hydroxide solution, slightly heated (no more than 50 degrees). The coins are then easily separated. The procedure may have to be repeated several times.
Speed up any cleaning it is possible by heating the solution to 50-60 degrees Celsius, but control must be constant.
After cleaning
The result of cleaning a copper coin by electrolysis
If the cleaning is successful and the coin has acquired a collectible appearance, it must be washed with soapy water, rinsed and gently blotted with a cloth. After this, let it dry for about 30 minutes and put it in a closed space (a bag with latches - a gripper, in an album, in a plastic capsule). Contact with air is harmful to metal, so the storage container should fit snugly around the coin and have no holes. You should also choose albums that are odorless, otherwise the fumes may lead to oxidation.
Bringing back lost patina possibly by various chemical methods and traditional methods. For example, you can add 50 g of copper sulfate and 5 g of potassium permanganate per liter of distilled water. Heat the solution until the first bubbles appear and place coins in it. Patina will begin to form quickly; it is important to remove the coins in time. This process requires experience and should be carried out valuable coins Recommended only by a specialist.
You can only touch coins with gloves or tweezers, so as not to leave sweat marks. Sometimes you need to change the location of the coin if the oxidation process has become noticeable on it. It's best not to store coin albums in new furniture, as the varnish can emit toxic fumes.
Sometimes coins are waxed or varnished before storage. This is not recommended due to possible adverse contact of the substance with the metal. It is also undesirable to keep coins in a soap solution for a long time to avoid exposure to fatty acids. It is permissible to gently rub copper coins with chalk powder, after which the chalk must be carefully removed with a dry cloth.
Photos for the article were provided by site users: drdd, Greenveresk, Romka1981, Roman959. The electrolysis method in photographs - user lisred.
Like the Phoenix, which has learned the joy of rebirth, the restoration of coins provides a chance to resurrect echoes of past greatness different country and peoples. It’s just that, once embodied in ringing gold, silver, bronze, copper and other metals, coins fade over time, age and rust.
And in order to return them to their marketable condition, they are cleaned and restored. But you should not rush to take radical measures, since inept actions can only cause harm. In some cases, darkened silver, tarnished gold, patina of different shades look especially natural and expensive.
Restoration and cleaning of coins: the starting point is the degree of preservation
A classification of conditions will help you navigate the whirlpool of eternal values, according to which the restoration and cleaning of coins will receive the right direction.
Of course, from the first real ones, which appeared in the 4th century BC. in Lydia, not much has survived. But even today, many other specimens pass from hand to hand, representing items of the eternal hunt of collectors.
With minimal damage and abrasions, and practically uncirculated, coins can correspond to the highest degree of preservation, indicated by the symbols: UNC or AU.
Good preservation (XF, VF and F) can characterize exhibits that have been in circulation for a long time, but at the same time have avoided significant damage. These coins have contrast in the pattern and the smallest relief elements are visible, and scratches, notches and burrs are not deep, but for the most part there is no metallic sheen.
When only large details and the main contours of the relief are visible, there are scratches and even nicks, and the inscriptions and date of minting are practically invisible, the condition is considered to be satisfactory. To mark it, the following icons are used: VG or G.
Coin cleaning and restoration: optimal recovery methods
An event such as cleaning coins and their restoration requires the supervision of specialists who know how not to harm the product. Are you afraid of damaging your coin by chemical or mechanical action on the surface? D
To begin with, just wash off the dirt from her with warm soap solution and a soft brush or cloth. This will be sufficient for gold and some silver samples. And in case of oxidation, you can use a solution of ammonia or a slurry of moistened soda. But in any case, the coin cleaning procedure will be completed by rinsing in clean water and drying with a soft cloth.
For copper coins, in addition to soapy water, table vinegar will work. How long the object remains in the solution (several minutes or hours) will be determined by its condition, size and type of plaque.
Extreme caution will also be required when working with iron and zinc coins, since rust can only be removed from them with a knife or scalpel. True, there is a chance to use diluted hydrochloric acid and a brush made of brass wire, but the main thing here is not to harm the drawing.
But coinage made of tin, lead and aluminum does not tolerate chemicals. To remove dirt in this case, it is better to use a glass brush and a felt or cloth cloth.
Cleaning coins: arguments FOR and CONS
Jewelry and pots definitely need cleaning, and cleaning coins does not always lead to increased value. The natural appearance and traces left by time give the exhibits a special historical and collectible value.
Be that as it may, the decisive voice will be only the voice of a specialist who owns the necessary devices and materials. Inept restoration often leads to the exposure of rowan trees, erased designs and shells, which does not add any value.
There are many ways to clean coins, but you should never use untested means, and it is better to experiment on items that are not of particular value.