What is “topping off”?
Once wine has been racked to secondary, it should be topped off. This means the wine should be within 1-2 inches of the stopper. If a large air space is left in the carboy, the wine will oxidize, turn brown and taste bad. When racking from primary, extra wine should be put into a smaller bottle (wine bottles with stoppers and locks) and used for topping off after each racking. This smaller quantity of wine should be treated the same as the larger one, as it is fermenting along with the rest. If extra wine is not available, a similar finished wine should be used. Water should be avoided if the quantity needed is more than 1-2 cups per 5 gallons. Adding water in greater amounts will water down the wine, making it taste watery and reduce the body.