The invention generally provides gypsum-containing slurries including stucco, a hydroxyethylated starch, naphthalenesulfonate dispersant, and sodium trimetaphosphate. The naphthalenesulfonate dispersant is present in an amount of about 0.1%-3.0% by weight based on the weight of dry stucco. The hydroxyethylated starch is present in an amount of from about 0.5% by weight to about 10% by weight based on the weight of dry stucco in the formulation. The sodium trimetaphosphate is present in an amount of about 0.1%-0.4% by weight based on the weight of dry stucco. Other slurry additives can include accelerators, binders, paper fiber, glass fiber, and other known ingredients. The invention also comprises the gypsum-containing products made with such slurries, for example, lightweight gypsum wallboard, and a method of making lightweight gypsum wallboard.