Bulk Aging
NOTE: I have never done this.
The biggest mistake the home winemaker makes is bottling his or her wine too early. When fermentation and clarification are complete and no new lees form, the wine is finished except for aging and bottling. Wine ages best in bulk because it takes longer for bulk amounts to be affected by temperature changes than for bottled quantities.
Two things quickly deteriorate the quality of wine. Heat is the first and greatest enemy of wine. Sunlight is the second. Wine ages best in the dark at 50-60° F. A cellar is the best environment because it is cool, dark and subject to the least amount of vibration and temperature fluctuation. Absent a cellar, an interior closet as far from the central heating unit and washer/dryer as possible is the next choice.
Bulk aging is the aging of wine in the secondary container in which it was made and with the airlock in place. This usually means carboys of 6-1/2, 5, 3, 2-1/2, 2, or 1 gallon sizes. The larger sizes are preferred, but I don't know any home winemaker who makes all of his or her wines in 6-1/2 and 5-gallon batches.
Full bodied red wines should be bulk aged for at least a year. Two years is better and three years is ideal. Few people achieve the ideal.
Light red and rose' wines should be bulk aged for at least six months. A year is better.
Full-flavored white wines should be bulk aged for at least six months, but a year is better.
Light, fruity white wines should be bulk aged for at least three months, but six months is even better.
Bulk aging in a carboy has one distinct drawback. You can't make any more wine in that particular carboy until the aging is complete. Even if you have four 5-gallon carboys, having one sitting idle for a year or two aging wine reduces your winemaking capabilities by 25%. Somehow, that seems wasteful.
Many stores sell drinking water in 5-gallon plastic bottles. The water costs $4 or so and the store requires a $6 deposit on the bottle. These bottles are made of food-grade plastic and are ideal for wine undergoing bulk aging. If you use bottled water anyway, this is a pretty good deal. If you're willing to forfeit the deposit, you can acquire 5-gallon aging bottles for only $6 each. Be advised, however, that some people are of the opinion that oxygen can permeate this plastic and oxidize wine thus aged. I have looked in vain for scientific evidence of this and have not yet found it. Use your own judgement.
The only drawback in using the 5-gallon plastic water bottles is that their mouths are bigger than glass carboys and you may not be able to find rubber stoppers big enough to seal them. A number 9½ robber bung fits most of these bottles. However, you may have to trim a thin edge of the top off as it tends to curl inward and prevent the bung from seating. An alternative is to cut a square from a quart-sized zip-lock freezer bag (thicker than the standard sandwich bags) and secure it over the top with a strong rubber band. Be sure to top up to within an inch of the top to reduce the threat of oxidation. Should a malo-lactic fermentation set in during bulk storage, the gas given off will escape under the rubber band but air will not enter the same route. It works well, but be sure to sterilize the plastic covering before putting it on the bottle.