Spring Mountain relies on the indigenous populations of yeast already prevalent in the winery; populations that have been built up over the years of winemaking. Yeast is sometimes added in pure cultures to musts when comparing comparing different crop levels from the same vineyard. Sometimes this is done to ensure that the lots will ferment identically.
Spring Mountain almost never supplements grape acidity by the addition of natural grape acids to the must. Though this practice is common in California, Spring Mountain's red wines have good acidity. Even if one lot is a bit low, the wines are always
in balance after assemblage. In fact, a lower acidity is sometimes positive given the strong tannins found in Spring Mountain's fruit. Adding acid and meddling with the wine's natural composition often hurts rather than improves wine.
Toward the end of fermentation a pure, commercial culture of malolactic bacteria gets added. This culture begins to grow in the fermenting must, and converts the grape's sharp-tasting malic acid to a softer, more mild tasting lactic acid. A malolactic starter culture is never added to a sluggish fermentation.