Wednesday, October 11, 2006

How to clean coins

Want to bring out the shine in those old coins Grandpa gave you? Think twice before cleaning them. If the coins are collectible or valuable, cleaning will almost always reduce their value—sometimes by as much as 90%—and cleaning won’t improve their grading (the standards used by coin collectors and dealers to evaluate a coin), so you should usually let them be. If, however, you’ve just got some old coins around that aren’t worth much more than their face value, but which you would still like to make more presentable, you can usually clean them up pretty nicely without damaging their surfaces too noticeably.


  1. Verify that the coin is not valuable. You can look the coin up in a coin price guide. For modern coins, you’ll need to know the date and the mintmark, if one is present. If you can’t make out the date, or if the coin is so stained or dirty that you can’t tell what it is, try looking at it with a magnifying glass. If you can’t tell if the coin is valuable, check with a coin dealer (or two, for verification) before cleaning.
  2. Wash the coin under warm, running water. Hold the coin by its edges; touching the surface can cause small scratches. If you want to protect the coin’s surface, don’t rub it. Just run the water over it for about a minute. The higher your water pressure, the better.
  3. Soak the coin. If unsightly tarnish, dirt or rust deposits, or other contaminants remain on the coin after a thorough rinse, soak the coin for anywhere from a few hours to a few days. For gold coins, soaking in very hot soapy water is best. For bronze coins—usually ancient coins—soak in distilled water (the minerals in tap water can further taint the coin’s surface if soaking for a long time) or olive oil—olive oil is a very gentle way to clean coins, but you may need to soak them for several weeks. Silver, copper, and nickel-clad coins can be soaked in distilled water or, to remove tough stains, white vinegar. A 5-minute soak in lemon juice may also be used on silver coins.
  4. Rinse the coin again. After soaking, thoroughly rinse the coin under very warm, running water. If the coin is clean enough for your taste, proceed to drying (described below).
  5. Lightly brush the coin. If dirt remains, lightly scrub the coin with a soft toothbrush and dish soap (toothbrush bristles come in a variety of firmnesses—you want one labeled as soft or extra-soft). Run the toothbrush under warm water to further soften the bristles, and rinse the brush and the coin frequently to avoid scratching the coin with the loosened dirt. Do not apply much pressure, and focus on brushing only the soiled area of the coin.
  6. Dry the coin. Pat the coin dry with a soft, lint-free cloth, and then lay the coin on a soft, dry cloth to finish drying. Do not rub the coin dry.
  7. Spot-clean encrusted dirt. Especially on ancient coins, there may be dirt that remains after soaking and brushing. To remove this, use a small, sharp implement such as a toothpick, precision screwdriver, or dental tools. Carefully pry and chip off the encrusted dirt, and try not to scratch the surface of the coin. You can spot-clean more precisely if you work under good lighting and use a microscope or magnifying glass.


  • Commercial coin polish can be purchased from coin dealers or hobby shops. While this may bring out the luster in your coin, it is still not advisable to clean a valuable coin.
  • Do not use abrasives on a coin. Always use soft cloth or tissue to clean the coin. Other, more abrasive cloths may scratch the coin to the point that it is ruined. Abrasive powders and household cleaners may also ruin a coin. Stick to gentle cleaning if the coin is valuable or if it holds special significance to you. If not, a quick and easy way to add shine is to use a pencil eraser and rub the dirt away.
  • Coin collectors and dealers rarely clean coins, but when they do they generally use either specially formulated “dips” (generally for silver coins) or ultrasonic tanks. Dips are chemical products in which you dip a coin to remove surface dirt or to brighten the coin and remove tarnish. They can be purchased from coin dealers, jewelers, or hobby supply stores. Ultrasonic tanks clean coins using sound waves in a water bath. Be aware that these methods can reduce a coin’s value just as easily as other cleaning methods, especially if you don’t know what you’re doing.
  • Learn to appreciate a coin’s patina. The patina is the thin layer of tarnish (the effects of corrosion and oxidation) that develops on coins over many years. Collectors value coins with attractive patinas, and the patina actually serves to protect the surface of the coin, so it’s usually better not to remove tarnish or try to make the coin look as shiny as possible.
  • If coin is not valuable you can use taco sauce from Taco Bell to burn the dirt off, to some extent.
  • If coin is not valuable you can also use Pepsi or Coke, it's gonna come off as shiny as the sun.
  • A soft vinyl eraser is worth a try too, to remove patina. Vinyl erasers do not contain abrasive particles, compared to the 'normal' erasers.


  • Avoid cleaning any coin if at all possible because a cleaned coin may decrease its value if not done properly. Cleaning a coin is only recommended to be done if the coin has been exposed to damaging external ingredients such as finger prints, sweat or food stuff.
  • Nothing reduces the value of a coin faster than cleaning it. A pleasant toning (the patina) on a coin can actually add value to a coin, but cleaning will damage this unique coloration that has taken years (sometimes hundreds!) to develop.
  • Don’t use household cleaners or strong chemicals on coins. At best, they are generally no more effective than other methods. At worst, they can quickly ruin a coin beyond all recognition.

How to Clean Really Ancient Coins

Notes and Cautions:

  • Not every coin needs to be cleaned!!

  • When you first start, practice on a coin that you can afford to lose. When you try a new technique practice on a coin you can afford to lose. Bottom line is, when starting out you will ruin some coins. It is unfortunate but all part of the learning curve.

  • The object of cleaning coins is not to reduce them to bare metal lumps. Your concern should be with removing dirt and encrustations and leaving the base coin alone. A coin with its patina intact is always worth more than a bare metal coin. Please see our section on patina for more information.

  • When using chemicals, always follow the manufacturers instructions for use and in mixing solutions. Many of the chemicals you will use are harmless, but for safety sake always read and follow instructions.

  • There is no one 'right' method for cleaning coins. What works for one coin may be an absolute mess for another. The best solution seems to be a combination of methods and experience. Experiment to find the conbinations that work right for you.

  • Pirates may have buried treasure, but if you are expecting to find rare or unusual coins in your uncleaned coins you will probably be disappointed. It is far better to look at it as a numismatic adventure. Cleaning ancient coins can be just plain fun and that is the way it should be approached.

  • The most valuable tool in your cleaning tool kit is not one you can buy in the store. That tool is patience.

  • Uncleaned Coins Discussion Group. Meet your fellow coin cleaners at this YahooGroups email list.

    From the yahoogroups description "A place where us "Bottom Feeders can congregate without the ridicule of the elitist of the hobby. A place for buyers,sellers and anyone with an positive opinion on this portion of the Ancient Coin collecting hobby can exchange anything relating to Uncleaned coins. This also will include Greek,Byzantine,Roman and Islamic coin. Any one with negative attitudes will not be allowed."

    For more information you can contact the listowner at:

As you gain experience in cleaning coins, you will find yourself building up a small arsenal of useful tools. Here are some suggestions about the tools that I have found useful.

  • A strong directional light. I use a goose neck reading lamp with a track lighting bulb that gives a highly directional light. It allows me to position the light anywhere and direct the beam where needed most. A must for the attribution process.

  • Brushes. A variety of brushes is useful. Include toothbrushes and stiff bristle brushes (plastic or fiberglass) in different sizes. If feel you must use metallic brushes, make sure they are brass, not harder metals like steel. Do not use brillo, scouring brushes, Dremel or similiar tools.

  • Small detail tools. Toothpicks, dental tools, straight pins and sharpened bamboo sticks are all possibilities. They are invaluable for working in small areas such as in between the letters of an inscription.

  • Cotton swabs and Q Tips. Good for applying solutions to selected areas of a coin. Also sometimes useful for cleaning lightly dirty coins.

  • Glass or plastic jars, preferably with lids. For mixing and storing solutions. Some of the solutions you will be working with are best kept confined. You only have to spill a batch of used olive oil once to realize the truth to this.

  • A handy source of hot and cold water. Good to have for mixing solutions and giving your coins a water rinse. For best results use distilled and de-ionized water rather than tap water. Tap water frequently contains chemicals or disolved minerals that can cause unpredictable results.

  • Stereo Microscope. Although expensive, I cannot say enough good things about the use of stereo microscopes when cleaning coins. A 10x power microscope will allow you to see an entire follis sized coin with high enough resolution that it makes cleaning a pleasure. In many cases all you will need in the way of tools is a needle or straight pin. With a stereo microscope and a needle you can place force precisely where you need to on a coin rather than on the entire surface. A decent microscope will run you $200 or more. Try to find one used, if you can.

Cleaning Techniques (silver)

Lemon Juice A relatively fast technique for a little light cleaning. Simply take some lemon juice (I have used the concentrate type found in most grocery stores) and allow the coin to soak for a few minutes. For fast cleaning I will use the concentrate straight from the bottle. If I want to go slower I will dilute it with distilled water. After three or four minutes take the coin out, dry and examine it. If the coin is clean to your satisfaction, give it a running water bath to remove any trace remains of the juice. Or let the coin soak in a dilute solution of baking soda and water.

Repeat as necessary, but if the coin does not 'come clean' within a few cycles then it is not likely too.

Note that as the lemon juice becomes exhausted it will turn an interesting shade of green.

A simple method for light cleaning. Does not work on all coins.
Ammonia A more corrosive technique than lemon juice, it can be tried for those hard to clean coins. To use simply follow the same steps you used for the lemon jouce soak. But be prepared to check the coin frequently.

A simple method for heavier cleaning. Does not work on all coins.

Finishing Touches

Once you are satisfied that a coin is about as clean as it will get, you will probably need to touch up some small areas on your coins or preserve it to keep it from corroding.

Small areas (for example between the letters of an inscription) can be cleaned with a steady hand, bright light and a variety of tools. Which tools you will use will depend upon your personal preferences and what you feel comfortable using. I have had a number of different tools suggested to me including:
  • dental tools
  • sharpened bamboo sticks
  • toothpicks
  • a glue gun

A special note should be made about the last one. Take a glue gun (the type that uses glue sticks and can be found in any arts and crafts store) and put a blob of glue on a coin. Let the glue harden and then remove it. The glue should be relatively easy to remove. If it works right, the glue will lift the dirt from the hard to reach areas. With a few reservations I can tell you that it works. When you pry the hardened glue off it pulls the dirt out of even the tiniest spot. It may not get all of it off with the first attempt so multiple applications may be needed. Make sure the glue has hardened before trying to remove it. The reservations are:
  • If you are working on a 'silvered' coin the glue may take the dirt and the silvering off at the same time. So don't use it on that silvered antoninianus.
  • If the coin has subsurface pitting, then the glue may expose the pits.
So, if you are careful about which coin you use it on, then this technique will work.

I would highly recommend that you practice on cheap coins first before working on the sestertius of Caligula that you've been wanting to touch up.

Coin Preservation and Protection

After you have gone through all of the trouble to clean your coins, now you want to preserve and protect them. To do so, some collectors coat their coins to seal out moisture and the environment. Some traditional techniques from the last century and still in use in Europe are to lightly coat the coins with bees wax or varnish. New products are available which include:

  • Blue Seal Coin Cleaner and Preservative. This product lightly cleans coins, coats (imparting a soft sheen) and seals them. I apply it with a QTip and wipe any excess off with a soft rag. It works, but has the drawback of slightly darkening the patina. Also, porous coins will soak it up like a sponge and darken considerably. The good side is that non-porous coins that already have a dark patina come out looking super. It is not for every coin and requires some care in its use. It is available in some numismatic supply stores. If you cannot find it, check the Book Seller List for information on contacting the Brooklyn Gallery of Coins and Stamps. They sell numismatic supplies as well as reference works.

  • Renaissance Micro-Crystalline Wax Cleaner / Polish. This is a product, imported from England, that is used by the British Museum for its collections. According to the description it "revives and protects, freshens colours and imparts a soft sheen. Dries instantly.". It is available in an 8oz tin from Art Rubino at Numismatic Arts of Santa Fe. If you want to give it a try, the phone number of Numismatic Arts is 505 982-8792 or email Art for availability and details. I have tried it and it works as advertised. Plus that 8oz tin will most likely last forever.

There is not much I can say about storing your coins that hasn't already been said. The one point that I would like to repeat is that if you use 2x2s, flips or any storage product that uses plastic, make sure they do not contain PVC (polyvinyl chloride). PVC will do horrible things to your coins over a period of time and may ultimately ruin them.

Non-PVC storage products are available through most supply houses. One of my favorite sources is the Brooklyn Gallery in Brooklyn NY. They carry a nice selection of numismatic supplies including the non-PVC flips. case any one is curious the name of my prefered flip is ET Safflip manufactured by the ET Kointain Company.

Art Rubino at Numismatic Arts of Santa Fe stocks Acid Free Paper Coin Supplies. They are "two by two" white paper, acid free envelopes for coins, and 24 mm [slightly less than one inch] in white only. The envelopes are white paper since they cannot guarantee acid free paper with the presence of any coloration. These are the very same supplies used by the British Museum in London for preservation of their extensive collections.

A Note About Patina

PATINA (noun), a thin film of corrosion, usually green, that forms on copper and bronze as a result of oxidation.

Doesn't sound like much, does it ?
The patina of an ancient coin has taken literally centuries to form and has helped to protect the metal of the coin from the elements and further corrosion. An ancients coins patina can appear as green, brown, black and many shades in between. It is part of a coins history and as such, should be left as intact as possible.

Consider that coins with a poor or spotty patina are generally worth less than coins with a nice even patina. Furthermore, the value of a coin that has had the patina removed can be severely reduced.

So, it is in your own interest as a collector and ancient coin cleaner to take care of your coins patina. Your objective when cleaning coins should be just to remove any dirt and incrustation that obscures the coins design and not to return them to the way they looked when they were first minted. Remember, don't clean them down to the bare metal. Ancients coins are not supposed to be bright and shiny.

Ancient silver coins can also have a form of patina on them, but we call that Toning. Toning can range from a very light to a very dark grey. A properly toned silver coin can be very pleasing to look at, as opposed to the bright silver coins that are so common today. So please, if you have a toned silver coin let it be.
note:outdated contacts removed

And atlast from 24 caret:
How to Clean Coins

The best advice we can give for most people about cleaning coins is...
We see far more coins ruined by cleaning than we see coins which have been improved by cleaning.
Generally speaking coins can not be improved by cleaning them. It is certainly impossible to improve their condition by doing so.
We first saw this advice in 1962 edition of Seaby's Standard Catalogue, and it still appears in the same book today, although it is now published by Spink.

If You Have To Ask - Definitely Do Not Clean Them!
It's true that if you had to ask about cleaning your coins, how to, or whether to, then the best thing for you to do is nothing. Don't clean them. You will almost certainly not improve them, and you are much more likely to spoil them.

We Occasionally Clean Coins
Never say never!
We occasionally clean coins, but then we have been in the business for over 36 years, so we know which ones might benefit from careful cleaning, and which will not.
We also know how to clean coins, and more importantly, how not to clean coins.
Even though we never clean coins unnecessarily, we occasionally get it wrong, and end up with a worse-looking coin after we have cleaned it.

If You Really Must - How To Clean Coins
First - Cleaning Gold Coins.
Because gold is a noble metal, it is unlikely to become discoloured. Wash carefully in warm, even boiling, soapy water (detergent is also OK). You may even brush it gently with a soft brush. Be careful, if there is any grit present it will make minute scratches on the surface.

Cleaning Silver Coins.
Silver acquires a tone through tarnishing. A pleasant, even tone can enhance the appearance and desirability of an old silver coin. Some toning has rich blue, green, indigo, and violet "oil effects", toning like this will be appreciated by most connoisseurs. Do not clean any silver coin with this type of toning.
If a silver coin is so dark brown or black that its design can hardly be seen, then it may, be worth dipping, usually in a proprietary solution, such as Goddard's Silver Dip. If in any doubt, don't!
Whatever you do, do not use any abrasive paste or cloth.
Warm soapy water may also be used.
Even if silver coins are carefully cleaned, they end up looking artificially bright and silvery. Many collectors will not buy a silver coins which looks as though it has been cleaned.

Cleaning Copper and Bronze Coins
Copper and bronze coins usually look awful when they have been cleaned. They are more easily ruined than silver or gold coins. Once again, the best advice is do not clean copper or bronze coins.

Leave It To The Experts
Usually, the people who ask about cleaning coins are those who have recently acquired them. They may have found them in old drawer, or been left them in the estate of a relative or friend. Because they find them difficult to read, they assume that the coins need cleaning. It's much more likely that their glasses need cleaning.
More often than not, right after we have finished telling these people not to clean the coins they have found, they ask us how to clean them anyway! It gets quite frustrating.
Archaeologists, expert numismatists, metal detectorists usually learn which coins may benefit from cleaning, and how to do it. These people will often use an ultrasonic tank. This is not a magic device, it merely uses ultrasound waves to agitate the liquid in which the coins are immersed. This will often be soapy water, and nothing more. Sound waves are gentler than a soft brush.
Many people now own miniature domestic ultrasonic tanks, sold for cleaning jewellery. Before you are tempted to clean your coins in such a tank, remember the advice we have repeatedly give above, if you are unsure - do not clean coins.

Cleaning Coins Spoils the Toning
As we have said for silver coins, it is easy to spoil a pleasing tone, which may have taken centuries to be acquired. Copper and bronze coins will almost always end up looking a brassy unpleasant colour after cleaning. Even gold coins can sometimes be ruined by removing a rich tone which has built up over a long period of time.

Avoid Abrasives
As we have made clear above, one of the easiest way to spoil coins is to scratch or abrade their surfaces by using an abrasive. Most cleaning pastes contain abrasive. Any sort of rubbing action should also be avoided, whether using the fingers or a cloth, especially polishing cloths which are impregnated with any kind of cleaning material, and which are usually sold for polishing.

Drying Coins After Cleaning
If you simply have to clean coins after reading this, be careful when it comes to drying them. Any rubbing action will scratch them. Dabbing or patting dry with a clean towel will be the best.

How Harmful Is Cleaning Coins?
Over 90% of the coins brought in to us by non-collectors are junk. Even so, junk has a value, and the value will be greater if the coins have not been cleaned. Assume someone brought us a box of 100 mixed coins which we were prepared to pay £10 for, if they had been cleaned we would be less interested, and may only pay £5, so cleaning would have halved the potential value for the owner.
Let's assume you found a mint condition1869 penny with its original mint lustre. For this great rarity, we would be happy to pay close to £1,000. If you cleaned the same penny with "Brasso", we would be reluctant to pay more than £100 for it. You would have destroyed about 90% of the coin's value by cleaning it.

1 comment:

Anonymous said...

This is what I always do and it comes out amazing I use the one with the shampoo