Red wine fermentations can be tricky. There are so many interacting phases. Extraction is key, but it must be controlled. Winemakers look to develop great color while retaining the best fruit characteristics of the varietal. They need to coax out those compounds that lend complexity and mouthfeel, along with enough tannins to give the wine a backbone but not so much that the wine turns astringent or chalky. CO2 produced during red wine fermentation pushes the skins to the top of the fermentor, ...