The author Christopher Ailsby shared with us the following information on the discussion forum of this site. In order this invaluable information not be lost in the shuffle of the forum a copy of the post is available here.

There are many ways of keeping a collection but care must be taken when selecting materials for use in the storage of medals, as corrosive gases can be emitted by a variety of substances. These gases are present in the atmosphere but generally at low concentrations. However, materials such as wood, fabric and adhesives used in a storage system may emit these substances, producing higher concentrations which can cause deterioration of objects in the storage area.

Silver is tarnished by reducible sulfides, commonly hydrogen sulfide and carbonyl sulfide, which can be emitted by fabrics, especially those made of wool and by some adhesives.

Copper and its alloys are corroded by chlorides, sulfides and organic acids. The source of these may again be fabrics but also certain plastics. For example, polyvinyl chloride (PVC) can give off gases containing chlorine.

Acidic papers and boards, wood, wood composites and some adhesives can release organic acids. The corrosion of lead is initiated by acetic acid and basic lead carbonate is formed. Formaldehyde, which is emitted by wood composites, can also corrode lead by the formation of lead formate.

As an extra precaution, an absorbent material may be incorporated into the storage system should an artifact be particularly prone to corrosion. Charcoal cloth, a fabric made from activated carbon may be used to absorb all types of gases. Zinc oxide pellets, which react with hydrogen sulfide and hence reduce the rate at which silver tarnishes, can also be used.

The usual form in this country, as well as on the Continent and in the USA, is a medal cabinet containing a number of flat trays and sooner or later the serious collector will have to consider the possibility of buying or making one. The price you will have to pay for a cabinet will depend largely on the quality of the workmanship and the number of trays it contains. Try to avoid buying a cabinet if the trays have been cut to take several shapes of medals on each tray. These have usually been made to meet the requirements of a particular collector and can be extremely inconvenient and space-wasting to anyone else. There are very few new cabinets being made at the present time.

Always remember when buying or making a cabinet to select mahogany, walnut or rose wood as other woods such as oak, cedar, etc contain a resin which is liable to put an unsightly tarnish on your medals and may prove difficult to remove without damage. Those specified woods are usually suitable for the storage of silver artifacts. However, in tests, lead almost always corroded and copper occasionally corroded in the presence of wood, especially oak. In general, when any wood is to be used, it should be well seasoned and dried. Tropical hardwood like mahogany are the least harmful. However, due to ecological factors, it is preferable that such woods are not used.

Adhesives are an important consideration. Cascamite (a powdered urea formaldehyde adhesive) is a general woodwork glue which may be used for construction of cabinets and inserts. Glues based on polyvinyl acetate emulsions should be avoided.

Wood-composites such as plywood, fibreboard and blockboard, are generally unsuitable for use with lead and often unsuitable for use with copper. This is due to harmful, volatile materials emitted by both the wood component and the adhesive or binder component. Manufacturers are becoming aware of problems associated with volatile gases and some types of fibreboard, e.g. Medite, are designed to have low level emissions of formaldehyde. These low emission fibreboards are often suitable for use, though testing of each type is recommended.

Plastic cabinets and trays are an alternative to using wood. At present, of those tested, only one type of plastic tray has been found to be suitable for use with all metals. Further information can be obtained from the British Museum. Plastic cabinets are also available for housing these trays. The cabinets have not been tested but presumably are made from the same plastic as the trays and thus suitable for use.

Stove-enameled metal cabinets may be used for storage of all types of materials.

Drawers or trays within the cabinets are often lined. Plastozote, a polythene foam available in a variety of colors, may be used as an insert with suitably sized profiles cut out to accommodate the medals. The foam will afford protection to the medals, as it will prevent them moving around and suffering mechanical damage when the drawers are opened and closed.

Textiles may be used to line drawers and trays. The use of felt or woolen felt discs should not be used in proximity with silver, as they emit sulfide gases that will cause rapid tarnishing. Other fabrics can also cause problems. A looped nylon fabric may be a suitable alternative, as it has smaller quantities of felt. It will not fray when cut, acts as a 'cushion' and is available in a variety of colors.

Another convenient method of keeping medals is in envelopes made from white paper, which may be kept in storage boxes long enough to contain between 150 and 200 medals. A description of each medal can be written on the outside of the white envelopes. Many envelopes are made of poor quality paper, which will become acidic and unsuitable for use in storage. Therefore envelopes should be made from archival quality paper or board.

In the United States and Canada by far the most popular way of keeping medals is in medal folders which may be kept in a bookcase. These have a number of pouches forming the page. Information such as name, date and numbers awarded may be printed on sticky labels placed on the reverse of the pouch. Although this is certainly a compact and convenient way of keeping medals, it does not compare with the more conventional and handsome mahogany medal cabinet in which the medals may be arranged and ticketed as desired. Some plastics may degrade and produce harmful vapor or droplets of plasticiser. Therefore, archival quality plastic envelopes should be used. These are made of polyester or high quality polythene. The coins or medals can be stored individually in plastic boxes such as clear, colorless polystyrene boxes. These may be lined with Plastozote foam to avoid mechanical damage.

It it usual to place medals on white circular tickets on which may be written a short description of the medal, its catalogue number and perhaps your own reference number. Most medal dealers supply their own tickets when selling medals and you may wish to keep these, while writing any additional facts on a second ticket of your own. It is also a good idea to make a separate list of your medals, either on a card index or on loose leaves. Better still, in this computer age, is a database that stores the information. Paper discs should be made of archival quality paper or board.

Inks used for annotating paper discs should have a permanent colour and be tested for acidity prior to use. Several pens have been tested by scientists in Glasgow. The following were found to be suitable for archival purposes; Artline Calligraphy Pen black EK 243, Edding Profipen 0.1 1800, Pentel Document pens permanent MR 205 (black and blue), GPO standard ballpoint pen PO SP15.

On occasions, whilst on display, silver medals have acquired a white 'bloom'. This has been shown to be a result of photochemical degradation of the original silver chloride patina, forming powdery metallic silver. It is unlikely that medals would be continually exposed to bright light whilst in storage but this potential hazard should be borne in mind."

For information on cleaning medals, please see the page bearing that name in this section.

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