How To Clean Coins

One of the most frequent questions asked by beginner coin collectors is “How do I clean my coins?” The answer is quite simple: DON’T DO IT!

Actually, that may be a bit of an overreaction. In reality, there are many instances when coin cleaning by someone less than a pro is acceptable. The DON’T DO IT shout down was to catch your attention before diving headfirst into a coin cleaning endeavor without proper consideration.

The objectives here are to (1) explain why coin cleaning can have a serious downside, (2) help you decide whether to clean or not to clean a particular coin in your possession, (3) provide some coin cleaning methods should you decide to proceed with the cleaning process, (4) what to do if you choose to seek professional help.

The Downside of Coin Cleaning

Basically, there are two types of coin cleaning: chemical and mechanical.

Chemical treatments: refers to dipping in commercially available liquid solutions, vinegar, soft drinks, lemon juice, and all sorts of concoctions. Reactive agents alter the coin’s surface at the molecular level, resulting in unnatural color and luster, both easily detectable if not done properly.

Mechanical cleaning: accomplished by physical force, such as buffing, polishing, abrasive action, or spot cleaning with a toothpick or some other device. These applications may leave a coin shiny and free of debris, but under magnification, damaging hairlines or other blemishes are visible. Ultrasonic cleaning and electrolysis also are forms of mechanical cleaning.

The main downside is that if you goof up while cleaning a coin, there is no hitting the “Undo” button to start over. If you ruin a coin, it’s ruined forever, and nothing can restore it to like it was before you got your hands on it. In the case of a numismatically significant coin, this mistake can cost you a lot of money, because collectors are less interested in coins that have been obviously altered artificially from their original state. It is not uncommon that a rare key date coin be discounted by 50% because of improper cleaning!

cleaned vs uncleaned coin example

Example of a cleaned coin vs an uncleaned coin

To Clean or Not to Clean

It’s quite easy to find a dirty coin, especially one that’s been around for a long time. Dirt, tarnish, corrosion, slime, and all manner of contaminants can detract from a coin’s appearance. The truth is that the vast majority of coins do not have much collectible value, if any, associated with them. If your dirty coin has very limited or no numismatic value, proceed forward with the cleaning process and have a clear conscience. In fact, think of it as a learning experience. Most coin cleaning experts got their start this way.

On the other hand, if have a coin in need of a little TLC that carries a bit, if not a large numismatic premium, DO NOT attempt to clean it, UNLESS you really know what you’re doing and are confident you can remove the unwanted adherents without leaving a trace of damage. Chances are you attained this level of expertise by practicing with coins of much lesser value.

If you are not a knowledgeable collector and are uncertain if your coin has numismatic value or not, but yet are thinking about doing a cleaning job yourself, the best advice we can offer is to not go forward, at least not right away. Do some reading up on coins and learn some basics about estimating coin values. If you don’t have the desire or time to do your own research and prefer not to consult with a dealer, drop in on an online coin collecting forum. Post some decent photos and ask for help. Pretty soon, scholarly forum dwellers will show up with loads of wisdom and honest opinions to guide you.

Coin Cleaning Methods

Once you’ve determined there’s little downside monetary risk to cleaning your coin, how do you go about getting it done? There are more cleaning methods than we have time to talk about. Some of them make sense, but a few seem to be the stuff of loony folklore. Let’s categorize the foreign substance types and mention a few effective methods of removal

Dirt: This may be one of the easier things to remove, but never abandon caution. Dirt has tiny abrasives integrated within, and will scratch the coin if you’re not careful. First, warm up some distilled water in a soft, plastic container, then add a touch of mild dish soap. Let the coin soak for at least ten minutes. Using your fingers or a very soft toothbrush, gently dislodge dirt particles from the coin’s surface. Don’t rub and use very little force. Rinse in another plastic dish of clean distilled water. Set the coin on soft cotton cloth and gently pat with another cotton cloth to absorb water, and wait for it to dry. Do not use paper towels, because wood fibers in the paper can leave scratches. For especially tough dirt deposits, soak coin in olive oil for two days before starting the cleaning process. Grease and petroleum oil may also be removed following these instructions.

PVC film: Many years ago, coin supply companies developed vinyl coin holders made with PVC as a softening agent. Unfortunately, long term storage in a PVC holder causes a slimy green film to form on the coin. What’s worse, the slime contains acid that may etch the metal. Millions of coins exist today afflicted with this slime “disease”. Pure acetone works well to remove PVC slime. Dip a cotton swab in acetone and gently apply to coin. You should start seeing the green gunk absorbed into the swab. Change out the swab frequently. Continue applying acetone until swab no longer turns green. Sorry to say, if the coin suffers from etching, the injury is irreversible. Warning: Acetone is flammable and gives off toxic fumes, so handle it accordingly.

Tarnish: Removing ugly tarnish may well be the trickiest coin cleaning feat to pull off without doing harm. In fact, it is so difficult, that many experts will not attempt to remove tarnish from a valuable coin. If you’ve got tarnish on a low value coin that is bugging you to death, you may purchase dip solutions from a coin dealer or online supplier. Be sure to correctly match the solution type with the metal alloy of your coin.

Lacquer: Coin collectors from long ago thought it was wise to preserve coins by applying a coat of lacquer. Today, lacquered coins are shunned, so much so that third party certification services refuse to grade them. Thankfully, lacquer can be removed with pure acetone, the same product used to cure PVC infected coins. Place your coin carefully in a glass dish and immerse in an acetone bath. Don’t use a plastic dish because the acetone could melt it. As always, be careful not to rub or use a lot of pressure, avoid paper towels (cotton is better) and use distilled water for final rinsing. Some lacquer coatings are extra tough, so this procedure may have to be repeated several times.

Seek Professional Help

Okay, let’s say you have a coin worth a considerable sum of money, but is in need of a good cleaning. If the coin were to be made more attractive, it would be easier to sell and fetch a higher price. Given your lack of know-how, you decide this is a job for a professional, and you’re willing to pay a service fee. How do you find a professional coin cleaner? You have several options:

National Conservation Service: There aren’t many companies offering coin cleaning services on a large scale, and of these, NCS is the best known. They are a sister company to the highly reputable certification service, NGC. They have a two-part fee structure. First, there is an evaluation fee to determine if it makes sense to provide conservation work on your coin. This charge is 1% of the market value of the coin with a minimum of $5. For conservation work (i.e. cleaning) their fee is 2% or 4% of the market value with a minimum charge of $15.More details are available at the NCS website.

Local Coin Dealer: There may be a coin dealer near your home who doubles as a coin cleaning expert. Many dealers are a member of the NCS network, so if you visit a neighborhood coin shop, you still may end up considering the NCS option. Most dealers will tell you truthfully if your coin is a good candidate for cleaning.

Online Coin Forums: Anytime help is needed on something to do with coins, whether the topic is cleaning or something else, online coin forums are a great resource. There are a few highly active forums with lots of veteran contributors. If you can post good photos of your coin, someone invariably will come along to help you decide if it’s worth the effort to clean and where (or if) you can get professional services in your area.