How I became a winemaker
http://www.youtube.com/watch?v=ifgwfEswocU
Here's a more scientific way to determine how the fermentation is coming along: use a hydrometer. Basically speaking, the hydrometer is a floating scale to determine the amount of sugar left in the wine. As the fermentation progresses, there'll be less sugar. In this video, the sugars are at 10% (or 10-degrees Brix...named after some German dude who invented this scale). To learn more about Brix, go to: http://www.kenswineguide.com/wine.php?word=18
Yay, the Chardonnay is fermenting! How do I know? Well, when it whistles, I know! Yeah, there are other ways to tell. I do get out my hydrometer to measure sugar levels. But I know things are going great when the relief valve on the bung is starting to sing!
You see, when the yeast eat the sugar in the grape juice, about 55% of it gets converted into alcohol. Much of the rest gets converted into carbon dioxide (CO2). The CO2 builds up pressure in the barrel and we use a special bung to let the gas escape. Otherwise the bung would get shot across the winery, or worse...the barrel would explode!