CLEANING COINS ALA NUMISMATIST

After long discussions here and on other sites, I bring you advice on cleaning coins from a professional numismatist and I think it is advice and experienceand they will help even the beginner prospectors who have been blessed on Hunters lately and whose coins sometimes shine with incredible luster

1) If you are a numismatic layman, do not unnecessarily engage in chemical or mechanical cleaning of coins, especially if you want to sell or donate coins, you should clean only those coins that you want to keep. The numismatic collector usually prefers to clean the coin himself, but usually also prefers coins with an original noble patina.

2) Dirt can usually be removed from a coin with plain warm water or soap. So if you want to clean a coin, use warm water and soap (but not for proof coins).

3) Simply cleaning a coin will not increase its preservation! Cleaning only removes the dirt from the surface, but the preservation remains the same. A numismatist does not judge preservation by the removable dirt on the coin, but by its overall condition (see my page on preservation). But a cleaned coin is obviously more appealing to the numismatic layman or beginner.

4) If you decide to clean the coin anyway, keep in mind not to physically damage the coin! The dirt can be removed, and after a few decades, the unpleasant luster of an unprofessional chemical cleaning of a copper coin may disappear, but the ray marks will remain on the coin forever! Similarly, if an iron coin catches rust due to unprofessional cleaning, you can slowly say goodbye to it.

5) Don't clean coins at any cost! The brown noble patina on copper coins, for example, is much more appreciated than if the coin tarnishes as a result of unprofessional cleaning. If the coin is in decent condition and if it is only slightly soiled in relief, don't clean it as well, you may harm it. Coins that are heavily soiled or tarnished (blackened, have a greenish surface, etc.) or are e.g. Coins that are not very well preserved (e.g., have a zinc plague) or that cannot be damaged by cleaning.

The following advice should be given to those who collect or intend to collect coins and would like to improve the appearance of their collection by cleaning some of them. The thesis that only cleaned coins should ever be included in a collection no longer applies without reservation. It is often better not to clean a coin than to damage it by unprofessional cleaning. Moreover, some modern coins do not need to be cleaned at all.

In principle, we distinguish between mechanical cleaning (e.g. removing dirt with a water brush, cleaning with a rag, rubberising dirt, etc.) and mechanical cleaning.) and chemical cleaning (soap, acids, detergents, toothpaste, use of special metal cleaning products). In some cases, the two methods are combined (when cleaning with Sidol, removing the dirt with a cloth on which the product has been applied, etc.). Another type of cleaning is ultrasonic cleaning. I can recommend this in general for all metals, but for little experience with this method I prefer it again for more common coins. However, a small Roman silver coin that I provided to an optician friend for this purpose looked excellent after ultrasonic cleaning!

GENERALLY:

If you decide to clean the coin, you should use plain warm water in the first instance. Often it is sufficient to bathe the coin in water or to soak it for a few minutes. If the dirt won't come off, use soap. Soaping your hands and rubbing the coin in your soapy hands is often enough. Always rinse the coin well in water at the end and dry it thoroughly (with a cloth or hair dryer). I have one improvement for today's modern times. I'm sure you all know about dishwashing sponges. Such a sponge (e.g. already used and no longer suitable for washing dishes) is an almost ideal tool for cleaning coins. Apply soap to the side with the sponge, which soaks into the sponge along with the water and forms a nice lather that the coin receives in batches. The other side (with plastic wires) can be used in place of the recommended baby toothbrush to carefully remove the copper buildup that didn't come off when just washing with soap.

INDIVIDUALLY BY METAL:

GOLD

Gold is quite resistant to corrosion, and gold coins are also found mostly in good preservation. It is usually sufficient to wash a gold coin in warm water. However, with a gold coin, there may be a problem in removing the unpleasant red stains caused by heat. For this case, special procedures based on special acid leaching of the coin are recommended.

SILVER

Try warm water or soap first. If this does not help, use one of the following procedures:

- for a less well-preserved coin that is tarnished, I recommend mechanical removal of the dirt with a surprisingly simple (and effectivem) way - you need an ordinary soft eraser for lubrication and simply "erase" the coin mechanically - it yields surprisingly nice results and the coin doesn't get too damaged either, don't put too much pressure on the eraser, rather erase the same spot longer to avoid unwanted microscopic grooves on the coin - not suitable for better preserved coins, of course, but water and soap will usually help;

- Alternatively, you can use children's toothpaste (apply to a cloth and clean the coin in your hand), but this is already chemical, so I recommend caution;

- this is a tried and tested old and fairly safe method of cleaning silver coins - place the coins in some sort of glass or plastic bowl (e.g. then pour a solution of citric acid in approximately natural concentration over the coins (a slightly stronger solution is possible, a large It does not affect the speed of cleaning) - leave it like this for a few days, usually two to three days are enough, it is recommended to change the solution once or twice a day, the acid can be helped in the final step with a soft (!) cloth;
- instead of citric acid, plain vinegar (8% acetic acid) can also be successfully recommended;
- an alternative is to repeatedly bathe the coin in alcohol;

ATTENTION! Never clean silver coins with different ratios of silver to base metal together in acid or alcohol! Chemical cleaning sometimes releases copper residues from the coin, which can in turn contaminate the silver coins. I strongly recommend cleaning coins either individually or together always only coins of the same grain.

- The following acceleration procedure can be used on all silver coins, even coins that were struck as proofs (as you can read in theYou can also read the "preservation" section, a proof coin removed from its original packaging should no longer be marked as a proof); so wrap the coin in a soft cloth and boil for about 5 minutes in a citric acid solution(one teaspoon in 3 dcl of water is sufficient) - the dark stains on the silver coin will disappear, the dirt will ideally remain on the cloth, I onceHowever, it happened that a coin minted as a proof "peeled off" together with the dirt and a kind of film remained on the coin (it was a Czechoslovak silver commemorative coin from the 1980s). perhaps it was Zapotocky)

COPPER and its alloys (MOSAZ, BRONZ)

With copper, more than with other metals, the only safe way to clean it should be with warm water. It is a principle that the cleaning of coins should not destroy the original, so-called noble patina. An old copper coin should have just the appearance of an old coin. The noble patina (brown or beautiful blue-green oxidised layer of metal) must be distinguished from the non-noble patina, e.g. spongy copper, which on the other hand should always be removed from the coin if possible. In addition to warm water, the following cleaning procedures can be used in special cases:

- for very tarnished and otherwise almost worthless coins, soft baby powder can be used on the corrosion or on the copper toothbrush, possibly with a low-aggressive toothpaste (but always try first, e.g. On the worthless 1851A Kretzar before you start with the Teresian Kretzars);

- for guaranteed completely worthless coins, feel free to use chemicals (sidol, neoxide, etc.), but do so at your own risk!

- this is not so much a cleaning method, but rather a sort of easiest method of restoring a coin - old copper coins are often so worn that their inscriptions are often completely illegible - sometimes a simple trick will help - just to place the coin on hot metal, or heat it over a stove - the details of the coin come out of the surface and the coin is easier to identify, again usinguse only with coins that cannot be identified in any other way, but sometimes the coin is so worn that even the fire won't help. Over a flame or on a stove, however, the coin may become undesirably discoloured. So choose well and again, choose carefully!

Bronze coins stand out a little from the crowd of coins made of copper alloy and other metals. Bronze is an alloy of copper and tin. In good quality bronze, a higher proportion of copper predominates and such coins are then cleaned in the same way as copper coins. However, coins made from low-quality bronze with a higher tin content can suffer from a rather unpleasant oxidation (called "tin oxidation"). "green cancer" of bronze), which is similar to the "tin plague" (see below under "tin"). Bronze cancer is very difficult to fight - for cheaper pieces, try a similar approach to the tin plague "disease" on a coin. Repeatedly heating infected Roman bronze coins in water to boiling point and then drying them using a soft cloth and a hair dryer has worked well for me.

As a point of interest for chemists: the literature (e.g. Nohejlová - Prátová) recommends heating infected bronze coins to 30°C for several days, then rubbing them with asphalt dissolved in turpentine and wiping them after a quarter of an hour. I don't know, I haven't tried. But such scientific methods are not for me...

Ancient bronze coins are the subject of specialized archaeological equipment, not chemical cleaners!
UNDER NO CIRCUMSTANCES USE CHEMICALS ON ANCIENT COINS!

ZINEK

With zinc we often have one unpleasant problem - white spots on coins, the so-called plague or "white disease" - these spots, like classic rust, are affected by the environment and spread over time.

There are two proven cleaning methods:

- coins that are less well preserved with white spots can be "leached" and in a solution of baking soda and water and then cleaned with a cloth;
CAUTION! This method is VERY DANGEROUS! Bathe the coin in this way for a maximum of 10 minutes and always rinse it very well with soapy water after cleaning with a cloth. In no case is it suitable for rare coins, where there is a risk of damage! However, this cleaning makes those annoying white spots disappear and they usually do not form again - ideal for common German or Protectorate

- The following "secret" recipe for cleaning coins was revealed to me by an old numismatist as a young elite during the totalitarian era:
-the zinc coin is lightly rubbed with sewing machine oil (but even better with gun oil) and then rubbed between the fingers or rubbed with a rag.The coin then stays in decent condition for a long time, I recommend to try again first on a worthless coin, some people may not like a slightly blackened coin;

ALUMINUM

These are mostly common, often worthless coins, if this is the case, try anything, even chemistry (sidol etc) in a pinch, it still usually doesn't help much on coins that are really tarnished. But sometimes mechanical removal of dirt and washing with soap and warm water helps, sometimes again ordinary soft rubber, but beware here, "gumming" can leave marks on soft aluminium!

IRON AND NICKEL

For more common coins, again possibly use chemicals, rarer coins again only with warm water and soap. But nickel will last quite a while, iron again is usually quite tarnished, often with rust. Fortunately, in the case of iron, again, these are usually low-value coins. But even here there are exceptions!

PRICE

Tin is fortunately not very common as a coin metal. In the last century, however, small folk medals were made from it in abundance, and there are also quite rare pewter coins. The cleaning of pewter coins and medals also has its specifics.

For dirty pewter coins, it is also recommended to use a tried and tested recipe - plain warm water and soap. However, a big problem arises when the coin is infected with the so-called tin plague. Tin plague is chemical in origin, if a tin object is exposed to an environment where the ambient temperature of the coin is below -18°C or above +160°C, it changes its structure and the metal turns into a white powder.

Warning. Tin plague is contagious! Therefore, never handle an uninfected pewter coin together with another pewter object that is infected with the plague!

Unfortunately, this also applies to a somewhat limited extent to the greenish unrefined patina of bronze coins, which is known among numismatists as the "green cancer" of bronze (see above).

It is recommended that infected pieces be completely separated or sealed in a plastic bag. Nowadays, small "medicine" bags, closed with a special plastic "zipper", are commonly sold. I highly recommend it.

And how to fight against tin plague? The literature lists various methods based on heating or boiling the coin in a solution containing decalcifying agents. Some sources mention, for example, a 2% hydrochloric acid solution. However, I know from my own experience that this does not help much.

OLOVO

Fortunately, there are not many lead coins either. There are, however, period forgeries made of lead or its alloys (e.g. forgeries made by Austro-Hungarian goldsmiths). Again, uncorroded lead can only be cleaned with warm water. I know of no way to clean corroded lead coins. I have not found any available method in numismatic literature either. Therefore, I recommend leaving corroded lead coins as they are after all the findings. The chemical reaction of lead with air produces a strange coating on the surface which is quite hard, but underneath this coating the metal is usually turned to powder. Cleaning can irreversibly damage or even completely destroy a corroded lead coin!

Source :http://www.numismatika.comBobanx

This is text taken from Pavel Frouz's book "Collecting Coins and Banknotes", author's website www.sberatelminci.cz, e-mail mince@atlas.cz

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