Wine/Grape Must Adjustments: A number of additives are available that can be used to improve wine balance or quality. Major additions should generally be preceded by home trials and tasting of samples of the adjusted wines. Common improvements to grape must and wine include adjusting acidity and tannin levels.
Tartaric Acid: Tartaric acid is the characteristic acid of grapes. Low acid grapes will benefit from tartaric addition; the wine will clear more readily and will keep and taste better. It should be added to any wine with a total acidity of less than 0.5%. As a rule of thumb, 1g per L will increase titratable acidity by about 0.1%.