Crystals of tartaric acid are viewed there through a stereomicroscope in cross-polarized light and magnified 250 times. Tartaric acid is an organic chemical that occurs naturally in grapes and other fruits, and forms the sediment in aged wines. Most commercial tartaric acid is obtained from the by-products of wine-making, it has a wide range of industrial uses including carbonated drink and jam protection, metal polishing, wool dying, and photographic development and printing processes.