When the flow stops, disassemble the press, crumble the press cake and repress. Most home winemakers crumble the press cake two or three times when pressing expensive grapes. Ratchet type basket presses can produce high pressures, but high pressures often produce harsh, bitter wines. Moderate pressures are desirable, and the fruit should be pressed slowly. Wine can taste flat and insipid when the acid content is too low.
Wine tastes too tart when the acid is too high.
Grapes grown in warm areas are often low in titratable acid. Titratable acid should be between 0.65 and 0.85 percent before fermentation. Small quantities of tartaric acid should be added to the must if the acid level is lower than 0.65 percent. Acid crystals should be dissolved in a small amount of water before the acid is added to the must. Stir the must well, and then remeasure the acid content.