Q: I am new to making homemade wine and I recently started my own batch of Pinot Grigio. A week in I realized that I forgot to put water in my airlock. The fermentation is still going on (I can see bubbles) and I now have water in the airlock. Tell me have I messed up the wine? Can I fix it if I have?
— Benjamin Adams • Brunswick, Maine

A: No worries, mate (as my Australian harvest interns used to say), you should be just fine. The water (I think water with a pinch of sulfur dioxide and citric acid is even better) in the fermentation lock is there to act as the final gas barrier between your fermenting wine and the air. Carbon dioxide gas from the fermentation exits, bubbling up through the water, while outside air can’t get in. Simple, brilliant and a bit of winemaking technology that’s been around for over a thousand years. Lucky for you, your fermentation was still going on when you did remember to put water in the airlock, so it’s pretty likely that not a whole heck of a lot of air had contact with your bubbling beverage. That is, your fermentation was actively off-gassing into the atmosphere, so the laws of physics dictate that while your Pinot Grigio’s carbon dioxide was going out, not a lot of air was coming in.    

However, had you neglected to have the airlock on the fermentation container when your fermentation was on its last legs or inactive, it’s likely you’d be hazarding some oxidative damage or some microbial undesirables making ingress. As a fermentation winds down to its last few degrees Brix, it behooves the prudent winemaker to start thinking about protecting the new wine from oxygen and outside microbial contact. At this stage, it doesn’t have that robust layer of carbon dioxide gas to protect it from air or oxygen-loving spoilage bacteria so it pays to be vigilant. Luckily, active fermentation (often the time during harvest when a winemaker is the most stretched for time and sleep) is a pretty forgiving time. This time, you skated by but I wager next time you won’t forget to put water in that fermentation lock!