Coins and medals are popular items to collect. Often there are family histories and anecdotes connected to these objects. Because of their small size, coins and medals are easy to store without requiring too much space. Traditionally, coins have been made from three metals and their alloys: gold, silver, and copper. The alloys vary: silver or copper in gold coins, copper in silver ones, and tin or zinc in copper coins. This last group is often referred to as "bronzes." In recent years, additional metals - iron, aluminum, and copper-nickel alloys - have been used in coin production.
Causes of Damage
All coins and medals (except relatively pure gold) are likely to show some deterioration over time, especially if stored in damp or polluted conditions. Dampness is especially damaging for copper coins that have been buried because it encourages corrosion. Sometimes, the corrosion products on the metal surface will contain salts absorbed from the soil that allow corrosion of any remaining metal to continue if moisture is present.
The accumulation of chloride ions on archaeological coins made of copper or its alloys can result in a condition called "bronze disease." Bright powdery green spots appear on the surface. If this corrosion process is not corrected, it can destroy the coin. Such corrosion problems should be treated by a knowledgeable conservator.
Pollution also damages coins and medals. Many materials used in manufacturing everyday objects emit organic acids into the air. These organic acids cause zinc, lead, and copper to corrode, resulting in a covering of white crystals. This corrosion is difficult to stop unless the source of the organic acids is removed.
Copper and silver will tarnish in reaction with hydrogen sulphide, a pollutant given off by decaying animal matter (which is naturally present in the atmosphere). However, some paints, textiles, and other household materials also emit some sulphur-containing organic compounds and these also cause copper and silver to tarnish.
Handling and Storage
Exposure to the air oxidizes metal, changing its color. This does not reduce the value of your coins. It is advisable though, if you are storing your coins for a long period of time, you store them in a controlled environment. A relatively constant, moderate temperature and low humidity are preferable for long term storage of numismatic collectibles. Placing packets of silica gel in coin storage areas helps control atmospheric moisture.
It is best to handle coins and medals by their edges and, if possible, to wear cotton or polyethylene gloves (not latex). Gloves protect the metal from the corrosive oils and acids found on our hands. This is particularly important with Proof coins, which have a mirror-like surface, because any mark on them can disfigure the coin and greatly lessen its value.
Many modern numismatic coins come encapsulated to protect the coin from damage. Do not remove the coin from its capsule whether it is a mint sealed holder, or a so-called "slab" from a third party grading service.
Coins that are not encapsulated ("slabbed") are best stored individually in coin holders called "flips" made of Mylar, a stable plastic. These holders have two pockets: one for the coin and one that can hold a piece of paper where you can write information about the coin. They come in a variety of sizes.
Somewhat more commonly available are cardboard holders lined with Mylar. These have a circle cut out in the middle that is covered with Mylar. The coin is placed on the Mylar "window" and the other half of the cardboard holder is folded over and stapled on three sides. Both sides of the coin are then visible through the Mylar. Be careful to flatten the staples against the card so that they do not scratch other coins they might come into contact with. Although the cardboard is not acid-free, it does not come into contact with the coin's surface. For the majority of coins, this kind of holder is fine.
Avoid flips and other kinds of holders made of polyvinyl chloride (PVC) because they can lead to corrosion of coins over the long term. Coin albums are not recommended because it can be awkward to remove coins from the pockets (they are usually open at the top, increasing the likelihood of coins slipping out when the album is open).
Many medals come with their own presentation cases. These are an important part of the object's history and value and, although the medal should not be stored in the presentation box, they should be kept together. Medals can also be stored in Mylar flips or holders. If you have medals without cases, you may want to consider using clear polystyrene boxes (available at plastic supply houses). These are affordable and provide good protection. Use a soft, nonabrasive packing material such as acid-free tissue or Microfoam (an uncrosslinked polypropylene) to line the box.
Wooden coin cabinets (especially oak) are not recommended for storing either coins or medals. They can emit acidic vapors that will cause corrosion. Instead, use metal storage cabinets (preferably with a powder coating) or containers made of either polyethylene or polystyrene.
Most numismatists advise against cleaning coins, and we at Superior galleries strongly agree. They often have patinas, toning, and tarnish that can develop on the surface of a coin over time. Certain kinds of light tarnishing, called toning, are considered part of a coin's value. In the case of Proof coins, it is very difficult to do anything that will not hurt the coin.
Removing surface dirt from a coin is about the only cleaning that should be done. When handling or cleaning coins, you should wear cotton or polyethylene gloves (not latex). To remove surface dirt, wash the coin in lukewarm distilled water with a mild liquid soap. Do not scrub the surface. To rinse, use a cotton swab dipped in distilled water. Regular tap water contains chlorine, which can leave chloride on the surface of the coin that eventually leads to corrosion. After cleaning, use another cotton swab and acetone to gently remove any grease (this is called degreasing) that may remain on the surface. Because of its toxicity, acetone should only be used in a well-ventilated area. Allow coins to air dry on a paper towel.
Coin dips or metal cleaners (cloths, liquids or pastes) are not recommended. The dips contain acids that can cause corrosion if any remains on the surface. Most metal cleaners contain abrasives that can scratch the coin.
Security and Your Coins
Security and your coins is an extremely important factor in today's world. We have heard literally hundreds of stories about thefts and mysterious disappearances of coin collections from one's home, sometimes where some very rare or unusual coins are now gone forever.
Always use common sense regarding the security of your coins. Most collectors like to keep their coins nearby to study them at their leisure. Isn't that what coin collecting is all about? Conversely, no collector wants to be the victim of a theft or mysterious loss.
Home Security - Whatever the size, when at home, your coin collection is at risk from theft, fire, floods, and other natural disasters. Depending on the value of your collection, there are several important measures you should consider for maximum protection: 1. a highly rated home safe that will withstand fire and theft. Sometimes, your insurance company might require a secure safe as part of the rider on your collection. 2. A monitored security system is also an important addition, if you don't already have one. Installation and monitoring costs are minimal in comparison to what most collectors stand to lose in the event of a fire or theft. 3. When leaving your house, whether for work, or an extended vacation, always leave the impression that someone is home. You can leave a radio playing, be sure to have your mail and newspaper picked up, leave one or more lights on timers, and put up signs indicating an alarm system is present, and "beware of dog" even if you don't own one. 4. Most thieves know the "typical" hiding places - master bedroom, home office, etc., however, they also know the longer they are in your house, the greater likelihood of their capture. A coin collection should be spread over several non-obvious locations, this at least partially foiling a burglar's complete success.
Bank Storage and Transportation - By far, bank safe deposit boxes, or private security vaults are your best bets for maximum security for your coins, but there are several additional factors to consider when renting one. Be sure to rent a box that is large enough for your collection and use silica-gel packs to reduce ambient moisture. Always remember that your greatest danger lies in the transportation of your collection to and from the bank. It's a good idea to have someone accompany you, avoid establishing a pattern when you travel with your coins, and always pay attention to what is going on around you; ie: another car is following you. Always carry a cell phone and don't be afraid to use it to call for help.
Shipping - Some times, you may have to ship coins to someone, and there are some steps to minimize or avoid loss. Never identify the package by addressing using the words: numismatics, coins, or anything similar; instead use initials such as SG instead of Superior Galleries. Always pack the coins securely so they do not rattle and give a hint to the contents of the package. When using USPS, consider Priority Mail with insurance up to $500 in value as a cost effective means. Above $500, use Registered Mail with Postal insurance up to $25,000 in value. Postal insurance will not pay above that level. FedEx and UPS are excellent choices, however, rare coins are specifically excluded from insurability on those carriers. You will have to have private insurance or ask the recipient if they offer private insurance that covers those types of shipments.
Insurance - Regardless of the security measures you employ, it's a good idea to supplement them with insurance on your collection. All collectors should be informed that most Home Owner's Insurance policies DO NOT cover your coin collection, or if they do, it's usually a minimal amount - $500 to $1,000. You would have to obtain a separate rider - often these are inflexible requiring numerous security steps (previously mentioned), and a great deal of inventory and appraisal assessments.
The Best Seven Ways to Ruin Your Coins
We will close with some important tips for making sure you do not damage your investments. We have found these are the best ways to most easily damage your coins that many beginning collectors do without even thinking about them. If you care about protecting the investment you're making in your coin collection, take the time to learn how to properly handle, clean, store, and protect your rare coins.
1. Touch Your Coins
Just touching your coins with your bare fingers is enough to cause damage to them, especially if you collect higher grade coins. And you will definitely damage them if your fingers come in contact with Mint State and Proof coins. Your fingers contain oils and miniscule pieces of grit that will adhere to the coins and cause them to discolor or suffer microscopic scratching. When you handle your coins, wear cotton or latex gloves, and handle only the edges.
2. Clean Your Coins
With the exception of freshly dug-up detector finds, cleaning or polishing your coins will do more harm than good. Once metal has been exposed to the air, it is natural for it to oxidize, or tone. If you strip the coin of this toning, not only will you lose any remaining mint luster, the coin will appear harsh and unappealing, and suffer microscopic abrasions that lower its grade. Plus, toned coins are worth more than stripped coins. If you really must clean them, clean your coins as outlined above.
3. Spit on Your Coins
Talking about your coins can do just as much damage as touching them or cleaning them, if you do so with the coins exposed while you chatter away. Little bits of saliva escape from your mouth when you talk, and these can cause spotting and discolorations that are difficult to remove. Many Uncirculated and Proof coins have been ruined this way. Say whatever you want about your coin collection, just make sure your coins are safe when you say it!
4. Break Their Holders
You are certain to greatly decrease the value of your mint set and proof set coins by removing them from the mint-issued holders they came in. The holders, along with the box and literature (if any) are part of the "set" and should be kept intact and pristine. Similarly, coins that have been "slabbed" (certified by a third party service) are worth a premium in their protective cases. Never remove coins from these types of permanent holders.
5. Expose Them to Acid
Storing your coins in envelopes, wrapped in paper, with your notations beside the coins, or in cardboard boxes is a good way to damage them unless you are careful to use acid-free paper materials. Over time, the paper material breaks down, releasing acidic chemicals around your coins. This causes spotting, discoloration, and can promote oxidation (toning) of your bright, mint surfaces. Be sure to buy only acid-free paper and cardboard supplies for your coin collection.
6. Coat Your Coins in Green Slime
Another good way to cause spotting and degraded surfaces is to store your coins in PVC-based plastic flips, holders, and boxes. Similar to the way the acid in paper can harm your coins, the chemical by-product of certain plastics can damage your coins over time. If you store coins in those handy food-grade plastic containers, or in soft, pliable coin flips, your coins will eventually develop a slimy green coating on their surfaces which will damage them permanently.
7. Expose Them to the Elements
If you store your coins in the attic or basement, you are probably exposing them to extremes of temperature and humidity that will promote their oxidation. In addition, these conditions will more quickly break down the storage materials (such as flips, paper and cardboard, plastic containers, etc.) your coins are organized in. To protect your collection the best, store it in a dark, dry, temperature-controlled environment (such as a safe deposit box or specialized coin cabinet.)