It is not uncommon for wine to absorb carbon dioxide, the gas created as a byproduct of fermentation. This especially tends to occur when fermentation slows to the point that bubbles escape the airlock at a rate slower than one bubble every 15 minutes. The positive pressure of CO2 in the headspace between the wine and the airlock bears equally on the wine and the liquid inside the airlock. Some of that CO2 is simply absorbed into the wine. The result is a wine that fizzes when poured. It may not fizz as much as a sparkling wine, but it greatly detracts from a wine that is supposed to be a still (nonsparkling) wine.
There are several ways to release this gas and return the wine to a true still wine. The simplest way is to simply stir the wine with a wooden dowel or a plastic rod. Stir the wine vigorously for about a minute and then replace the airlock and let the wine settle down for 30-45 minutes. Then repeat the procedure several times until the wine stops giving up CO2 gas. I use a plastic rod used to pull curtains closed. I heated one end of the rod in boiling water for a few minutes, layed the heated end on a wooden cutting board, and gently tapped it with a wooden mallet to flatten the end of it into a narrow “paddle” shape. I sanitize it by standing in upright (paddle-end down) in a 22-inch hydrometer test jar for 5 minutes filled with sulfite solution. I then put the paddle end into the carboy and attach the other end to an electric drill. This is undoubtedly safer than using a wooden dowel because the plastic cannot absorb bacteria or mold the way the wooden dowel can.
There are several products out there which are essentially a long rod with spring-loaded folding blades at one end. The opposite end is inserted in an electric drill and the blade end inserted into the carboy. The blades unfold inside the carboy and the electric drill is turned on. The propeller-style blades are raised and lowered throughout the body of wine to degasse a greater volume. After 30 seconds or so, the drill is turned off and the rod is withdrawn from the carboy. The airlock is refitted and 30-45 minutes later the procedure is repeated. This procedure works much faster and better than simply stirring with a rod or dowel, but my “paddle” works just fine for me and so I’m staying with it.
A word of caution when using an electric drill. Obviously, you do not want to get the electric cord or the electric motor wet, so be careful. Also, when you first insert the paddle or propeller-type device, tap the trigger a few times for just a couple of seconds to see how much gas is in the wine. If there is a lot, foam will erupt from the mouth of the carboy that — at worse — could shoot up into the electric drill before you realize what is happening and electrocute you. Just to be safe, wear heavy duty rubber gloves. At the very least it will be a mess to clean up, and of course will reduce the volume of your wine. Go slowly and be safe — and don’t forget the rubber gloves!
After a wine is degassed, it should sit for a while under airlock to “recover” from the procedure, as degassing a wine tends to “flatten” its taste for a couple of months. After sitting under airlock for the prescribed period, the wine can be bottled.
Source: Jack keller Wine