Whistlin' Dixie

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!