Oxidation is one of the major faults in homemade wine, and much of the oxidation comes from excessive head space in wine storage containers. Consequently, keeping the head space as small as possible is most important. Winemakers use the term "topping up" to describe the process of keeping wine storage containers full. Although topping up is very important to wine quality, beginning winemakers sometimes have trouble devising satisfactory methods. Here are a few suggestions.

1. Five or more percent is lost when a new wine is racked off the gross lees. Additional wine is lost each time the wine is racked, so making 10 to 15 percent of extra wine is a standard winemaking procedure. The extra wine can be stored in 5-gallon, 1-gallon or 1.5-liter containers. Of course, these containers must also be kept full.
2. Top up with any similar wine available. Most red wines are not significantly changed by small additions. Even small quantities of white or blush wines can often be used. Of course, red wine cannot be used to top up white wine. Cabernet in the Chardonnay is seldom appreciated.
3. Top up with a commercial wine of the same type. The major disadvantage with this method is the cost of the commercial wine and a slight dilution of the primary wine.
4. Use inert gases such as nitrogen or argon to fill the head space. Carbon dioxide gas must be used with care because it is quickly absorbed into the wine. The disadvantage of this method is the cost of the gas, the gas storage container and the regulator.
5. Add enough water to fill the headspace. The disadvantage here is the added water produces a small change in wine acidity and some flavor dilution. Many home winemakers shy away for water addition, but small additions of water are not noticeable in some wines.
6. Add clean, sanitized marbles to the storage container to bring up the wine level. The disadvantage with this method is that sediment becomes trapped under the marbles, and the sediment makes racking more difficult. In addition, the marbles role around when the container is moved, and the movement stirs up the sediment.

Most home winemakers prefer to use the first method, so they make extra wine specifically for topping up. Winemakers also acquire an assortment of different size carboys, jugs and bottles, so they can always find just the right size wine storage container.