Head of Stanley Gibbons' Commonwealth Department George James writes about the principal concerns in the preservation of philatelic collections: the ability to control the environmental conditions in terms of relative humidity and temperature.
Philatelic material should be stored in darkness at a temperature under 18° centigrade.
A previous article discussed the use of wine coolers for storage. It is important to note here that minor short-term fluctuations of humidity in the coolers should not be a cause for concern. Therefore, without the fan being turned on, with the door kept tightly closed, and the temperature set at 12°, the cooler will create its own microclimate.
Even in cases where wine coolers are not practical, or safes have already been purchased, staying inside the ‘golden zone’ is relatively simple in temperate climates, and can be achieved for little cost.
Preservation Equipment Ltd and Conservation by Design sell PelSorb and PROSorb, respectively, a moisture-sensitive silica gel capable of both absorbing and desorbing moisture, with formulas available which preserve the ideal level of humidity.
This can be placed inside a wine cooler, safe, or cupboard.
Stamps are a particular challenge to archivists as they are not only paper but in mint condition have the gum to deal with as well. Too damp, and you get toning/foxing, too dry, and the gum will start to harden and crack.
The Smithsonian National Postal Museum in the US stores their collection at 50% humidity, with the British Library aiming for less than 55%. Given the highest standards held by both institutions, relative humidity of anywhere between 50–55% should be considered the golden zone.
There are numerous humidity loggers on the market, the most basic of which can be purchased for under £20. Among the best, however, are ‘HOBO’ sensors made by a company called Onset. These data loggers measure and transmit temperature and relative humidity readings via BlueTooth to your mobile device. They cost in the region of £100 but are the best on the market for philatelic conservation—and in a setup which includes wine coolers, the temperature and humidity readings can be viewed through the glass.
In terms of storage, acid-free paper and plastics are of course as important. We offer a range of papers and plastic protectors that are all archival standard, acid-free and guaranteed to be safe for any treasures you wish to store.
Keep your stamps in appropriate albums, in darkness away from direct light, inside a wine cooler, with temperatures at 12° and relative humidity between 50-55%.
If the ‘ideal’ is not possible in your home, keep the collection in darkness and take steps to get the accurate temperature and humidity correct. Thousands of pounds have been lost on badly stored stamps ruined by toning.