What's The Rules For Topping Up Wine

When making my wine I have never topped up on the first or second racking. I have had great results but a few people tell me I need to be topping up the wine. I could see topping up the wine if I was batch aging, but for the 4 weeks I hold and rack after primary fermentation I am no so sure. It should be mentioned I am usually only down much less than a liter. Your thoughts?
Name: Mike in B’ville
State: NY
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Hello MIke,
If you are making wine from a box wine ingredient kit topping up the wine is not recommend. Partially for the reasons you gave about it not being that long of time, but also because these kit manufacturers produce the wine in such a way that they do not oxidize very easily. This is just one of the many advantages of using a wine ingredient kit.
However, if you are making a wine from fresh fruit or fresh juice the story is a little different.
First off, you don’t need to be topping up the wine while the fermentation is occurring. This is because the CO2 gas (carbon dioxide) coming off the fermentation keeps the air away and protects it from oxidation. The CO2 is slightly heavier than air, so it wants to create a protective blanket across the surface of the wine.
Even when the fermentation has completely stopped, as long as you have not taken the air-lock off the fermenter, there is no reason to be topping up the wine.  The CO2 gasses from the fermentation are still trapped in the head-space of the fermenter. No air is in the head-space.
But the moment you remove the air-lock or take the lid off the fermenter, all the rules change. You are then in a situation where not only is topping up important but vital to the color and flavor of the wine.
What is topping up a wine?
What is meant by topping up a wine is increasing the volume of the wine so as to reduce the amount of head-space in the vessel. To be more specific, the exact goal here is to eliminate as much surface contact between the wine and the air. You want this contact to be as minimal as possible.
In the case of a carboy, when you increase the volume of the wine you push the surface of the wine from the shoulders into the neck. It goes from maybe a square foot of surface contact area to maybe 2 square inches.
Hope this info helps you out,
Ed Kraus
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Ed Kraus is a 3rd generation home brewer/winemaker and has been an owner of E. C. Kraus since 1999. He has been helping individuals make better wine and beer for over 25 years.