The crushed grapes are placed in a lined plastic "garbage can".
To ensure a good fermentation, a few ingredients should be added. Above are two of the most common ingredients. Peptic enzyme breaks down the gelatinous pulp into juice by attacking the natural pectin in the fruit. (this is the opposite of making jam where you want the pectin to make the fruit jel.)
The yeast nutrient, while not absolutely necessary, is generally good to put in. Think of it as a fertilizer for the yeast which is supplying necessary nitrogen and phosphorus. (remember, yeast is a plant) While the grapes do have some nitrogen in them, if the fermentation runs out of nitrogen, hydrogen sulfide (rotten egg smell) may form ruining the wine.
The third ingredient (not pictured) is sulfur dioxide usually supplied as a sulfite. This may be supplied in several forms, the most common of which is either potassium or sodium metabisulfite. (I use the potassium salt). When placed in solution, they liberate sulfur dioxide. Virtually ALL wine contains sulfites as it is a necessary part of fermentation. The sulfite acts as both a preservative (anti-oxidant) and also serves to kill off the native yeast.
Yeast is the key to fermentation. They are in the plant family and are all around us. Many are quite useful, others can cause infections. The most common yeasts are bread yeast (used to make bread and rolls), brewers yeast (used to ferment barley, hops, etc into beer and ale), and finally wine yeast. They all work in a similiar manner, that is, they convert sugar into ethanol and carbon dioxide. In baking, the carbon dioxide is used to make the bread rise and the alcohol is driven off by the heat. (it is the alcohol that carries that wonderful smell of baking bread, but the EPA considers that a pollutant and makes commercial bakeries filter it out of their exhausts.) In brewing and winemaking, however, it is the carbon dioxide that is vented into the atmosphere (except in champagne where it forms the bubbles), and the alcohol is retained in solution. Grapes come with native or wild yeasts living on their surfaces. While it is possible to make a wine using the wild yeast, a cultured wine yeast will produce a more reliable wine. The sulfite added in the previous step will kill off virtually all of the natural occuring yeast. Wine yeast has a higher sulfite and ethanol tolerance that then wild varieties.
Here I am proofing the yeast. I have taken two packets of Lalvin "Bourgovin RC 212 Saccharomyces cerevisiae" and added them to approximately 120 ml of warmed (~105F/40.5C) juice and let them sit for 15 minutes. The crushed grapes will then be inoculated by pouring this into the crushed grapes. Fermentation will usually be going full speed within 24 hours.
For further information on wine, beer, and baking yeasts, go to: http://www.lallemand.com/
Twenty four hours after innoculating the must with yeast, a cap of skins and pulp has formed. I have punched down the middle but the piece of oak I use for stirring is actually being supported by the cap. The must needs to be punched down and stirred two or three times a day. During the next four days of fermentation, this cap will become 5 to 6 inches thick.