- Numismatic Questions
- Cleaning coins
Recently I’ve tried to clean the silver coin and just screwed it. That is how the idea of asking experienced numismatists to share some thoughts how to clean the coins arose.
Is there any universal way of cleaning?
Would it be better to say the universal way of cleaning doesn’t exist?
Is there anyone who has tried the coin cleaning paste? Is it effective? http://www.leuchtturm.com/epages/leuchtturm_eu.sf/en_IE/?ObjectPath=/Shops/leuchtturm_eu/Products/321584
Ultrasonic cleaners: Have anyone tried them? Are they useful? http://www.leuchtturm.com/epages/leuchtturm_eu.sf/en_IE/?ObjectPath=/Shops/leuchtturm_eu/Products/346740
There is also one important question I’d like to ask – if anyone had bad experience of coin cleaning (damaging it for example) could you please share what were you doing. For to avoid of repeating the wrong methods.
Thank you in advance Keaton
From my long experience, the best way to clean any coin, is NOT CLEANING. Or, as i'm doing, just water, neutral soap and a smooth toothbrush, just to remove the dust. I know there's some coins that looks much better cleaned but i prefer my coins like they are, without cleaning.
Hi, I totally agree with zimpeto. It takes away the history of the coin :)
I also agree with Zimpeto. I haven't seen a beautiful cleaned coin so far. Has anyone any example to give about the coin which is more beautiful after cleaning than before. If the reason for cleaning is to improve the grade, then it's called more familiar term: cheating. Coins grade is what it is, it's not about cleaning. If the original mint luster is gone, then it's gone. If the luster is made by cleaning the absolute max grade for the coin is VF. Fully are cleaned coin can't be XF, it's always VF or worse. No matter if the coin is silver, copper or brass, those are anyway better to leave as those are. The only excuse to clean the coin or part of it is to get important details visible for idetfying the type, mint or date.
I have a large collection. It's from BC era to modern commemoratives. Myself I love the most the "dirty old coins" branch. Coins have their patina, nicks, corrosion, damages. It's all part of history of the piece and somehow the piece with a high grade does not have, lower grade coin has the history of using the payment method through ages. Of the cleaned piece this history is taken away and it's a crude ugly type coin only.
Dear collectors: if you feel that you need more trade value for the coin than the catalogue gives for it. Please grade the coin right and add then the overvalue on the coin just as you see it best. Please don't improve or overgrade the grade and highen the value that way.
7 years ago
But there should be professional ways for cleaning coins? Like they do in museums for example.
I don't understand why they would clean or polish coins in museums? Dust and such stuff are easy to clean with water and soft soap. For heavy conservation to get the details readable is best to use a week olive oil bath to make the thick patina more soft and removing is best to do with plastic/wooden sticks. Electrolysis is also possible to use to remove thick patin or to get dark silver coins shine, but as I wrote the result is not neccessary very attractive when a circulated silver coin shines like new...
I don't recommend cleaning any coin with anything other than soap and warm water, However.. For cleaning back to the original colour use a mild acid solution then a polish, for aluminium even weaker solution, Museums use small picks and brushes for concretions the use ultrasonic cleaning devices like a dentist For a test with an old penny try cola and a pencil eraser. See youtube
Please never clean coins, coins cleaned are very ugly. Only thing you can do is to remove material not coming from coin metal, as dust, dirty or similar with a very soft cloth or paper without use water, acid or basic products. Assolutely forbidden cleaning products or cleaning machines. You obtain only a coin no more collectible. Coins in very fine cleaned dont become unc but only a coin in very fine ruined, ugly to see, Enrico
I totally agree with Zimpeto and Aki.
The best way to clean a coin is...... don't clean it at all.
But may happen you have a handful of coins which are worthless and pretty dirty. In this case you can feel a compelling desire to clean them....
Well, if you want some hints how to clean some coins (and what you must absolutely avoid), being aware that you won't improve its value (and.... let me say, its beauty), you can read a little artilcle I wrote few years ago. You can find it here:
Marco - WisardCoin
Here's one heavily polished silver coin on sale:
Hard to say that it's more beautiful than it would have been before cleaning. Is it now XF or UNC, if before polishing it was perhaps VF.
7 years ago
Nice article! Thanks for sharing.
7 years ago
I also prefer not to clean coins. But I soak zink coins into WD-40 for a few days. They look much better after :)
I don't recommend cleaning, Please do not use any chemicals to clean coins for the currency loses its numismatic value, this is a wrong practice.
Thanks for your answers! A lot helpfull information :)
Now maybe someone can share experiences with coin cleaning paste and sonic cleaners?
I have been a dealer and professional numismatist since 1968. The question you address is not a simple one with simple solutions. There are too many ifs, whens, buts and howevers.
Coins should never be cleaned unless there are exceptional circumstances involved. Most coins NEVER require cleaning. This is true for most modern coins, that is, coins struck with milling by modern machines which create uniform coinage. The only time these coins should be cleaned is when there are foreign matter (dirt, encrustations, etc.) on them, and then, only lightly to remove the foreign matter. Some toning, I admit, is ugly enough to be removed, but in general, don't touch them.
When dealing with coins before modern times (old coins pre-500BCE, ancient coins 500BCE-500CE, medieval coins (Byzantine, medieval, eastern 500-1500CE) and early moderns (1500-1700CE), cleaning is sometimes justified and usual. Again, only when necessary and with the least amount of surface damage.
I will flatly point out that we discount modern cleaned coins heavily when buying, by at least a full grade (average 2 grades) or more depending on the issue. Any artificiality also is damaging to the value.
If you insist on cleaning coins, find a professional. They are few and far between.
I have a related question.
I amici wittenessing the following phenomena:
I put my coins made by metal including cupper, in album with page Made of,plastic with small places for single coins
after some time (also some years) I take out the coins, and they are covered by a kind of slighthy sticky patina without color, that dissapears after gentle fretting with a cloth
what do you suggest in this case?
Hi, I agree, coins should not be cleaned, but somecoins should be cleaned if they are new and just plain dirty. NO chemical should be used. I tried withmild acid and wasted teh coin.
If the coin does not have intricate design on it then maybe you can heat it in soap water. expansion of the metal dfoes loosen dirt.
Every single metal needs different way of cleaning. A chemical that is suitable for one coin can be quite harmful for another. There are lots of ways and recipes of coin cleaning, however the main is – patience and great responsibility. So, armed with both of these, firstly clean the dirt and soil from the coin using water and soap.
Next step – it’s really important to pay your attention on what kind of rust is there on the coin:
If the copper coin is covered with the dark red (kirsch) rust, they have to be cleaned either with the ammonia solution of 5-15% or with ammonium carbonate solution (NH4)2CO3 of 5-10%.
If the rust is dark green (cupric carbonate) – in that case citric acid of 5-10% should be used.
If the rust is yellowish (lead carbonate) – you should use acetic acid solution of 10%.
If you wish your cleaned coins look not like the new ones, then you should preheat them in the solution of 80 degrees; preparations of solution: take 1 liter of water pour in 50 grams of copper sulphate and 5 grams of potassium permanganate.
If you have antique copper or bronze coins which are covered with such called noble platinum that appear naturally and makes the colour of the coin nicely brown and green (and with more other shades), it’s better not to clean such coins at all. Coins with such features are of even bigger value.
It’s much more harder to clean silver coins. As they were minted it was rarely pure silver used, almost always the copper was added, that is why the silver coins usually cover with green copper oxide. In that case the most proper way of cleaning is by using the mortar of sulphuric acid of 5% or formic acid of 5-10%.
If it happens that coins are stuck together (it happens often in treasures) then you should put them in to the mortar of sodium hydroxide of 5-10% that is heated to 30-50 degrees. After you clean the coins you must boil them several times in the water (distilled is better) and dry them up in the temperature not higher than 100 degrees.
You can not take the coins out of the chemicals using metal tweezers.
The best and most suitable way to clean gilded coins is using the piece of cotton wool that is soaked with turpentine, ethyl alcohol or methylated spirits.
You can use chalk to clean zinc, galvanized steel, copper, brass (brass) products.
Products of copper and brass also can be cleaned with the solution of oral or caustic soda. If you wish to refresh the gloss of the surface, you need to boil them in the solution of caustic soda for 30 minutes (40 grams for 1 liter of water).
I've read your interesting post. Thank you for sharing these info.
It is a very interesting discussion about how to face the coin cleaning topic with chemistry. I'm thinking to update my article (please ref the above posts) with new arguments, and this is would be a good topic.
May I include your suggestions in my article? If you need more details, please visit my website http://en.wisardcoin.it and drop me an e-mail or just reply here.
If I were you I would not use most of Maida's methods:) Acid especially. What a horrible thing to suggest Maida:) How will you stop acid continuing eating the metal? Eventually you can loose all the coin:) NEVER NEVER USE ACID.
DO NOT WASH COINS WITH WATER AND SOAP. Water corrodes (you won't see that immediately but it starts microscopicly first); even best soaps have %2 or more acid in them. Acid is our enemy.
My wife is a conservator working in a museum cleaning coins. She was horrified with me when she saw me washing coins! So she taught me some simple methods for many of the modern coins:
1- Do not clean them unless they really are dirty (circulating coins dirtied by organic substances like grease from handling). All coins are made out of alloys, never pure metals (even gold coins) and any method you use will have different effects on different metals forming the alloy. Some metals start corroding faster than others.
2- For gold, silver, bronze, copper and many of the hard alloys used today (apart from aluminium and zinc, do not use these with alcohol) soak coins only in pure alcohol (sold in pharmacies or chemical stores, not the spirits!). Never soak them in water! Water is a catalizer for corrosion! Remember rust? Alcohol is the best substance to fly away/dry fast. You can soak coins in alcohol depending on dirt and corrosion.
3- Then use cotton swaps to clean the coins while wet with alcohol. I sometimes finish rubbing the coin with a velvet cloth.
4- Make sure your coin is dry when finished. And this is it. This would solve 99 percent of your problems.
5- With iron alloys do not soak too long in alcohol. Zinc and aluminium coins should not be cleaned at all.
If your coin is corroded but ancient and important, the cleaning should be done by a professional, not you:) In museum labs they use microscopes to clean coins. More importantly in museums coins are covered in BTA and paraloid after cleaning so that they will not corrode again. And they are stored in acid free and humidity free enviroments. None of these can be managed perfectly at home...