Bottled wines are dramatically affected by the environment in which you store them. In fact, proper storage conditions are so important to ensuring that your wine is at peak quality when opened, that they should be considered the last unwritten step in the winemaking process. Commercial wineries usually age their wines in bottles, and we prefer bottle ageing for our wines as well.
Some wines are more susceptible than others to poor storage conditions. In general, white wines – particularly off-dry wines and Champagne – are more frail than reds. Grape variety can also make a difference to how well the wine does in storage; so you would find that Cabernet Sauvignon wines are generally more resilient than Pinot Noirs. However, no matter what the wine, it always pays to minimize the risks associated with bottle storage.
Temperature: Constant temperature is the key. By causing the wine inside the bottle to expand and contract, swings in temperature rapidly ruin bottled wine. Ideal cellar temperature is 7-13C/45-55F. Lower temperatures slow the maturation, though the extra time allows more complexity to develop. Wine could be safely stored to within a degree or two of freezing, but it would take decades to develop. On the other hand, wine could be stored at temperatures up to 20C/68F, where it would mature quite rapidly. Temperatures any higher than this will quickly damage the wine.
Light: Sunlight and ultraviolet light (ie. fluorescent lamps) are as bad for wine as excessive heat, but these problems are usually much easier to overcome. Though most wines are protected to some degree by coloured glass bottles, place your bottles in areas away from direct light, or else cover them with a blanket.
Humidity: Some degree of humidity is beneficial for long term storage, to ensure that the exposed end of the cork does not dry out and allow oxygen into the bottle. But beware of air conditioners, since they actually suck moisture out of the air. Ideally, the relative humidity in your storage area should be between 60-75%. Humidity higher than that encourages mould growth, not to mention label deterioration.
Movement: Wine does not take well to constant movement or vibration, particularly if there is sediment present, meaning that a secure storage space is a must. Don’t put your bottles next to the washing machine, for example, or in a storage area where they will often have to be moved to reach other items. Secure storage should also mean storing bottles horizontally, allowing constant contact of the wine with the cork, preventing the cork from drying out and letting air in.
Do a simple check of all environmental influences in or near your storage area. For example, areas such as garages or attics, which seem cool, may be subject to temperature fluctuations due to lack of insulation. A good option for a secure storage space is to insulate a small room, large cupboard or area under the stairs – an area that does not contain any heat sources like a water pipe or a boiler.
To be sure the temperature is stable, check it periodically with a thermometer. A good way to do this is to put a floating thermometer in a one-litre (one-quart) jug of water, and leave it covered in the space for 24 hours. This will let the water stabilize to the ambient temperature, and give you an accurate reading.