Stable, non-friable, non-dusty and fast-dissolving detergent additive containing bodies having a shape of substantially rounded particles of a size ranging from 100 to 2000 µm are disclosed, each body comprising a core particle comprising a solid particulate storage-sensitive detergent additive material and an organic binder material having a melting point from 25° to 80°C, which core particle is provided with an outer coating of an organic material having a melting point below that of the binder material and solubility in water at 40°C greater than 20% by weight, said bodies having a pore volume of not more than 0.25 cm³/gram and compression strength expressed as compression modulus greater than 0.5 x 10⁶ N/m². A process for preparing the bodies by a high shear energy mixing process in a high-speed mixer/granulator. Preferred detergent additive materials are peroxyacids and a peroxyacid bleach precursor.