A process for the production of an exothermically reacting composition, such as a propellant or explosive, containing at least one normally solid reactive constituent comprises the steps of: forming a uniform dispersion of the ingredients of the said composition in a carrier liquid; forming droplets of said dispersion; feeding said droplets into a cooling medium at a temperature below the freezing point of said carrier liquid to form solidified droplets; and freeze-drying said solidifed droplets.