On Saturday, October 18, I got half a ton of really nice pinot noir grapes from a highly regarded local vineyard. After processing the fruit -- destemming and lightly crushing some of the berries, and adding sulfur dioxide -- the grape must has been soaking in my cold garage before fermentation starts.
First, I have the must in three Rubbermaid bins beehived to create as much of a thermal mass as possible, and still allow me to move the bins around a bit without a forklift.
The cold soak allows the grape skins to give their color and flavors to the juice early in the winemaking process. The goal is to extract as much as possible before alcohol is present, because alcohol is a solvent that will pull astringent qualities out of the seeds, skins, and any stem parts in the bins. That's going to happen to some degree, as sugar becomes alcohol during fermentation. The idea is to have any of that happen at the end of the process, rather than crushing the grapes, fermenting the juice to wine, then letting everything sit for days and days until the wine has everything from the grapes that you want. So far, there's lots of color in the juice.
After several days of this cold maceration, I took some juice and gapes from each bin into a tub and brought it into the house to make a fermentation starter. Rather than adding yeast, I warmed the starter and allowed fermentation to happen spontaneously. Already it's beginning to bubble with the temperature close to 70F.
Once I get the bins up to around 65F, I'll add this starter in part to each bin to prime the fermentation. Heating the bins means heating the garage with a space heater, rotating an aquarium heater through each bin, even parking a warm car in the garage to keep the air temp up. If I get any funky smells, such as ethyl acetate that smells like nail polish remover, I'll entertain using dried yeast to get fermentation going. So far so good, and in my experience I've never had an issue fermenting without adding yeast.