Tartrates: Harmless crystals resembling shards of glass that may form during fermentation or bottle aging (often on the cork) as tartaric acid naturally present in wine precipitates out of solution. Components of tartaric acid, including potassium bitartrate and cream of tartar, are less soluble in alcoholic solutions than in grape juice and solidify at cooler temperatures (such as those found in a refrigerator); can be avoided in finished wines through cold stabilization. Decanting and careful pouring can prevent transferring the crystals from the bottle into the glass.
Sediment: As red wines age, color pigments and tannins bond together and fall out of solution, producing a natural sediment. While the sediment is not harmful, it tastes bitter and adversely affects the wine’s mouthfeel. Sediment is most frequently found in older (10-plus years), darker red wines, which typically have more color pigments and tannins, such as Cabernet Sauvignon, Bordeaux and Port. Rarely will lighter reds throw sediment.
Tartaric Acid: The principal acid in grapes and wine; contributes to taste and stabilizes color. Unlike malic acid, tartaric acid does not decline as grapes ripen. Tartaric acid can precipitate out of solution in bottled wine to form harmless tartrate crystals resembling shards of glass.