The character some wines possess of being somewhat syrupy and slow to move around in the mouth. Alcohol gives a sense of richness to wine only up until the wine is about 13.5% alcohol by volume. Higher in alcohol than that, wines actually taste thin. Neither alcohol nor glycerin makes a wine viscous. However, the ripeness of the grapes, residual sugar, yeast extracts, additives, peptides, polysaccharides, and proteins could all play a role.