Caring for your Collection
The information on this page has been taken from Chapter 9 of "Canadian Numismatic Correspondence Course" and is used with the kind permission of the Canadian Numismatic Association. You can check out the Educational section of their website for more information about this excellent course of studies. Chapter 9 of the course was written by Susan Maltby and provides much more detailed information that what we have been able to reproduced here.
NOTE: Comments by the CNS webmaster are written in italics and are not part of the original CNA source material.
More information about collection storage and handling can be found on the Canadian Coin Reference Site. Just click on the appropriate link from the drop-down menu on the left.
The information given on this page represents ideal handling and storage situations. There is a great amount of discussion concerning the appropriateness of various materials used for storing numismatic items as well as the precautions one should take in handling them. As individual situations vary considerably, no website can be a definitive, exhaustive source of information on this subject. Feel free to contact us with individual questions and we will do our best to help you.
"Most collectors can attest to the value of their numismatic collections. Coins and notes can be expensive to obtain and tend to go up in value over time. Storing a coin or bill in an inappropriate holder can damage it and cause it to depreciate. Properly housing your numismatic collection is not difficult if you know how to choose an appropriate holder for your needs. Properly handling the items in your collection is equally important. The irreparable damage that mishandling causes to numismatic collections can be avoided if you take certain precautions."
Susan L. Maltby
Our skin contains oils and acids that can have a deleterious effect on both coins and notes. Handling a coin with your bare hands can leave it coated with acids that will eventually etch or eat into the surface of the metal.
Either leave your coins in their holders when viewing them or wear gloves while handling them. The glove should not be made of a material which can, itself, be harmful to the coin. Cotton, vinyl or latex gloves or "finger cots" are the best.
Many professional museum staff are moving away from the traditional cotton gloves because they increase the risk of the item slipping out of your hand, particularly is the object is small or heavy.
If you must handle a coin with you bare hands, wash your hands first and thoroughly dry them before handling the coins. ALWAYS handle a coin by their edges.
It is a good idea to handle coins by their edges even if you are wearing gloves. Without your knowledge, small pieces of dirt and debris can be present on the glove which can damage the coin's surface.
Support bank notes with another, stronger, piece of paper, especially if the note is fragile.
Whenever possible, handle a coin while seated at a table and place a cloth on the table where you will be handling the coin. This way, if the coin is dropped, it will fall a short distance and the cloth will cushion its fall.
When assessing a holder, ask yourself if it fulfills all of the following criteria:
It should be see-through: A good holder should allow you to view the coin or note without removing it from the holder. Removing a piece from its holder places it at risk. A coin can be dropped or mishandled and a note can easily be torn or stained.
It should be made or a safe material: Safe materials are stable (non-degradable), as pure as possible (free of plasticisers and slip agents which can leach out and damage coins and notes), and acid free. If a plastic changes its properties over time (i.e., turns yellow or becomes sticky, brittle or cloudy), it is not a stable material.
It should be easy to use: You should be able to insert or remove a coin or note without damage to the piece. Coin holders should not abrade or scratch the surface of the coin.
This may seem to contradict the first point, but there is often a need to remove coins from their holders. Collectors often write information about the coin on the holder which may have to be appended or corrected. Also, you may need to remove the coin for evaluation or authentication purposes.
It should hold the coin firmly but gently: A coin should not roll around inside its holder.
Recommended Materials: Polyethylene, polypropylene, polystyrene, Mylar D tm (polyethylene terephthalate), Kodar tm (similar to Mylar D tm), and Plexiglas tm (polymethyl methacrylate).
Most of the inexpensive, 2x2, cardboard holders with see-through windows are covered in Mylar and are safe to use. The three-ring binder pages which are often used to store the 2x2 holders are, however, quite another matter (see below).
Questionable Materials: Cellulose acetate (acetate) was once considered safe for archival storage but is rapidly falling out of favour as it has been found to degrade, giving off acetic acid.
Materials to Avoid:
Glassine: Often acidic
Ployvinyl Chloride (PVC): The plasticisers in PVC tend to leach out of the plastic causing notes to become translucent and coins to corrode, producing what collectors refer to as "green slime". Even if the PVC is not plasticised, there is a risk of it releasing hydrochloric acid.
Using the Beilstein test, I have tested several brands of three-ring binder pages marketed specifically for the storage of 2x2 coin holders and have found them ALL to contain PVC. This may or may not be a problem as the corrosive effect of PVC may only be an issue if the coin is in direct contact with the material. There are, however, several types of pages marketed for the archival storage of 35mm slides which do not contain PVC and I, personally, choose to err on the side of caution and use these.
Polyvinylidene Chloride (Saran tm): Has been used to coat otherwise safe plastics and can release hydrochloric acid
Paper Envelopes: Not see-through and the quality of paper is often in doubt. Can abrade coins.
Coin folders: The blue type of cardboard folders, used to store coins by type, having holes in the cardboard into which the coins are pressed. Most are made of acidic cardboard and require considerable force and handling to insert and remove a coin.
Coin Tubes: Coin tubes allow coins to abrade one another.
Wooden Coin Cabinets: Traditional and attractive but not recommended as the wood is inherently acidic. the flocked or velvet lining of these cases is also problematic and coins can move around when the drawers are opened and closed. Enamelled metal cabinets are recommended as a safe alternative to wooden ones. Wooden cabinets can be made more safe by painting them with an acrylic latex and lining the drawers with an acid-free barrier.
Testing Materials' Suitability for Numismatic Storage
NOTE: The tests in this section, particularly the Sniff, Beilstein, and Burn test should only be conducted by adults, or under adult supervision, in well ventilated conditions.
Sniff Test: Avoid plastics that have a strong "chemical" odour.
NOTE: This test should be conducted by adults in a well ventilated area.
Needed: Small propane torch, copper wire, pliers, the material to be tested.
Heat the copper wire in the flame of the torch until it burns cleanly. This serves to burn off any unwanted residues that might be on the wire. Make sure that you hold the wire with pliers or an insulator to avoid injury.
Touch the hot wire to the material being tested. Some of the material will melt and be stuck to the wire.
Put the wire back into the flame. if the flame burns yellow or clear, no PVC is present. If the flame burns bright green, then some PVC is present. The one exception is Teflon tm which tests positive. However, there are no coin holders made of Teflon so you need not worry about confusing Teflon tm with PVC.
Stretch, Tear and Burn Test: Pull on the plastic to see how easily it stretches, try to tear the plastic as you would a piece of paper, ignite a sample and observe the resulting odour and rate of burn. Do this test in a well ventilated area and do not inhale the fumes directly as they may be toxic. Only adults should conduct the burn test and only under well ventilated conditions.
Recommendations for Holders
Notes: Housing paper notes is far less problematic than housing coins, medals or tokens. Ideally, notes should be stored flat and unfolded in see-through holders made from an inert, stable material.
Coins Tokens or Medals:
Flips: Coin flips are the most commonly used coin holders. They are inexpensive and provide good protection as long as they are made of safe materials. Their only drawback is that coins, especially small ones, tend to slide around in side the holder. Try to choose one that is close in size to the coin. Some examples are:
Blue Ribbon Safety Flipette tm
Mylar D flips tm
Coin Shells: These holders fit the coin exactly or have a foam insert ring which holds the coins firmly in place within the holder. Some examples are:
American Tight Fit Coin Sheets tm
Air Tite Holders tm
Cardboard flips: these flips are probably the most readily available and the least expensive to obtain. Although the cardboard is acidic, the coins are isolated from the cardboard by the plastic window, which is made of Mylar tm. These flips are considered safe for coin storage provided the staples used to close them are pinched back to keep them from nicking other coins when the holders are stacked together.
Never let the oils and acids on your fingers come in contact with the surface of a coin.
Make sure that you keep coins, tokens, medals, and bank notes in holders that are made of safe materials, that allow easy viewing, and that prevent pieces from moving around or being scratched or abraded.
If you are unsure whether your holders are safe, use the tests described here to determine what the material is and replace any unsafe holders with recommended ones.