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More on Storage
 | By Mike Thorne, Coins Magazine
November 04, 2008 |
Last month I ended my discussion of coin storage methods with a discussion of Capital Plastics holders, their advantages and disadvantages. This month I'm going to give you a bottom line on coin storage methods.
To this point, I've mainly highlighted some of the drawbacks of commonly used coin storage methods. The key question in this column is: What is the best storage method for your coins? The answer is going to sound like a cop-out, but here it is: It all depends.
For one thing, how you should store your coins depends on how long you plan to keep them. If you're primarily a coin dealer, then you probably don't plan to keep your coins long enough for the method of storage to become a significant factor. Of course, if you plan to keep your coins forever, which really means throughout your lifetime and perhaps the lifetimes of your heirs, then how they're stored is a major issue.
Another factor is the type of coins you have. If you have primarily well-circulated coins that have developed an appropriate patina with age, then your storage method will be less crucial than if you have mainly high-grade uncirculated and proof coins.
Coin consumer advocate Scott Travers lists a number of commonsense rules for coin preservation in The Coin Collector's Survival Manual that are worth summarizing here. First, and I talked about this earlier, you should store your coins in a cool, dry place. One obvious possibility is to keep your coins in a safe deposit box at your bank. The bank is almost certainly air conditioned, which should ensure a constant temperature and low humidity.
Travers notes that not all bank safe-deposit-box rooms are ideal for coin storage. Some apparently are kept relatively humid so that important stored documents will not dry out, and you obviously want to avoid high humidity. Also, some may have ozone purification systems designed to kill microorganisms. According to Walter Breen, such systems can have a rapidly deleterious effect on silver and bronze coins.
Coins should be kept away from paper, as the sulfur in paper can quickly tarnish high-grade silver and bronze coins. Again, the type of coins in your collection (well-circulated vs. uncirculated and proof) is the key here.
You should also avoid storing your coins in albums with plastic slides that cover the obverse and reverse of the coins. If the slides actually contact the surface of the coins, frequent movement will cause hairlines or wear to develop.
Coins should be stored in as airtight an environment as possible. At this point, it may occur to you that certified coins (slabbed, encapsulated) are well protected from environmental contaminants. After all, aren't the slabs made of inert plastic and sealed to be airtight?
Unfortunately, they're not really airtight. I know this because chemist Weimar White exposed encapsulated silver dollars to high levels of hydrogen sulfide gas, which is a common environmental contaminant. What he observed was that all of the dollars, even though slabbed by major service, developed some tarnish over time.
Obviously, most of us live in environments free from high levels of hydrogen sulfide, but the point of the experiment was to show that the slabs were not impervious to an airborne contaminant. Even if the environmental levels of the gas were quite low, storage of slabbed high-grade coins for long enough in such an environment would result in tarnish developing on the coins.
Travers concludes his list by advocating the use of a product called Metal SAFE Corrosion Inhibitor and by mentioning Intercept Shield preservation products. Metal SAFE is available from E&T Kointainer Co. and also from other dealers in coin supplies, such as Brent-Krueger.
In literature on the Brent-Krueger Web site, I read the following: "METAL SAFE Vapor Capsules contain a unique vapor phase inhibitor. When the capsule is removed from its sealed polyethylene bag, it begins to emit an invisible, odorless, nontoxic vapor which is diffused throughout the surrounding atmosphere until the air is saturated. The vapor then [protects] the metal surfaces against atmospheric corrosion by reducing the electrochemical activity of the metal surfaces."
A single Metal SAFE block provides protection for a year for a large safe deposit box. An unused capsules will last for five years if it's not removed from its sealed bag.
The Intercept Shield technology has been used to produce coin holders for individual coins and also coin albums. Again citing literature on the Brent-Krueger site, "when corrosive gases come into contact with the Intercept Shield material, they are instantly neutralized. The Intercept Shield reacts with the gases in a permanent and irreversible chemical reaction, thus actually cleaning the environment around the coin."
Coin albums made from Intercept Shield material will have a double layer of protection, both from the album itself and also from the slip cover for the album. The Intercept Shield albums are moderately expensive, but are apparently a good way to house a "raw" collection. In other words, if none of your coins are encapsulated, then the Intercept Shield technology is the way to go.
If, on the other hand, you have mostly slabbed coins, as I do, then adding a Metal SAFE corrosion inhibitor to your lock box and replacing it annually would appear to be the preservation method of choice.
More on This Topic from Mike Thorne:
Selecting a Holder
More on Cleaning
More Advice on Coin Cleaning
Cleaning Coins
To Clean or Not
Getting Organized
Where to Begin - Suggestions for a Better Approach to Coin Collecting
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