When you hear the words "topping up" it might bring to mind several things--like "topping up" a glass of wine, or adding more gas to the tank of your car. In reality, these thoughts wouldn't be too far from what "topping up" means to the home winemaker.
What Is Topping Up in Wine?
Topping up, simply put, is the process of adding more volume to a batch of wine so as to fill any void space that may exist in the wine's container while it is in bulk. To put it another way, it means getting rid of any large airspace that may exist with a wine.
The reason we are concerned about airspace is because we do not want the wine to come into direct contact with air for any significant length of time. With time, air equals oxidation; air equals the growth of unwanted micro-organisms; and in more severe cases, air can equal the complete spoilage of a wine.
Brief periods of air exposure are of little to no significance to the quality of the wine. It is longer periods that concerns us--days or weeks. This amount of air exposure can bring about these negative effects on a wine.
When Does Topping Up Wine Matter?
It is important to understand when topping up really matters. For example, during an active secondary fermentation, when the active fermentation is under an wine airlock, topping up is of no issue at all. This is because the fermentation creates CO2 gas that drives out the air that is in the airspace. This CO2 gas has no negative effect on the wine and is, in fact, a great protector of the wine.
In the case of the beginning primary fermentation, topping up is of no issue because the wine yeast actually needs air during this time. Air significantly aids in the yeast's ability to multiply itself. This is also one of the reasons a wine airlock should not be used during the primary fermentation. It cuts off the much needed air.
So, when does topping up matter? Very simple. It is when the fermentation has completed and no more CO2 gases are coming off the must. This is when topping up the wine becomes valuable. This is the time when air exposure needs to be dealt with. The wine is no longer being protected by the CO2 gases from a fermentation, and any air that is in the container with the wine at that time can actually come into direct contact with the surface of the wine.
What Should You Top Up With?
There are many ways you can go about topping up a wine. How you tackle the job depends, in part, on how much headspace you are dealing with. If you have a 5 gallon batch with just a pints worth of headspace, you would handle the job differently than if the headspace were a gallon or more.
Topping Up Wine With Water
The most common means of topping up a wine is to simply add water. This is appropriate if your head-space is around a pint or less per 5 gallons of wine. Distilled water is preferred. It can be purchased at any full-line grocery store, or you can use tap water that has been boiled for a half hour or so and then cooled down to room temperature.
The idea here is to use water that is void of free oxygen. Distilled water has no free oxygen and by boiling tap water you can remove a significant portion of its free oxygen.
Topping Up Wine With Vodka & Water Mix
If your head-space is closer to a quart, you can still use water but you might also consider adding some Vodka to the water as well. By doing this the alcohol level of your wine is not being diluted. Any cheap, 80 proof, American Vodka will do. Just add it to the water at the rate of 4 ounces for every quart of water you use.
Topping Up Wine With More Wine
Another option is to incorporate a wine from a previous batch or wine that was commercially made. Obviously you would want to select a wine that is similar to the wine being topped up. This is a good option in the sense that you are maintaining flavor and body as well as alcohol.
Topping Up Wine With Glass Marbles
You may also want to consider using glass marbles in the wine to add volume to the batch. The marbles need to be sanitized first with one of the many safe sanitizers we offer.
The biggest disadvantage with using marbles is that they have the ability to crack or break a glass vessel. For this reason, we suggest that you be very careful when using marbles. The last thing you want to do is crack a carboy when it is full of your precious wine.
A Combination of the Above
Also realize that any combination of the above methods can be incorporated together as well. For example, maybe you don't have enough glass marbles to get the job done. Well then use some wine or Vodka water as well to finish the job.
Switching to Smaller Containers
As a final note, if you are dealing with a serious amount of head-space, then usually the best option is to put the wine into a smaller container or a number of smaller containers. For example, if you have 6 gallon glass carboy with only 4 gallons of wine in it, then your best option would be to move the wine into 4 one gallon glass jugs.
There are a couple of other ways you can deal with air exposure in a fermentation or storage vessel. For example, instead of topping up, you can dissolve 2 or 3 crushed Campden Tablets into each 5 gallons of wine at the very end of fermentation. Then put the wine airlock back on the vessel. This will cause any airspace in the vessel to fill with SO2 gas from the tablets. This will create a protective layer of gas on the wine.
Or alternatively, if you do not open a fermentation vessel after the fermentation has stopped, the CO2 gasses from that fermentation will stay trapped in the fermenter, again, creating a protective layer of gas on top of the wine.
Both, SO2 gas from Campden Tablets and CO2 gas from a fermentation are heavier than air and will linger in a given space.