A storage-stable, readily-soluble detergent additive comprising particles, at least 70% of which have a diameter within the range of 0.1 mm to 1 mm consisting of from 1% to 75% by weight of at least one active material enhancing the washing, bleaching or biocidal effects of a detergent, substantially surrounded by and embedded in from 25% to 99% by weight of an enveloping material consisting of a mixture ofA. from 20% to 90% by weight of said mixture of at least one compound having a melting point above 30.degree.C, selected from the group consisting of fatty acids and fatty alcohols,B. from 0 to 50% by weight of said mixture of at least one water-soluble compound selected from the group consisting of poly-oxy-lower alkylene glycols, non-ionic surface-active compounds and anionic surface-active compounds, andC. from 1% to 40% by weight of said mixture of at least one water-insoluble but water-swellable compound selected from the group consisting of salts of acrylic acid copolymers and methacrylic acid copolymers. The invention also relates to the method of producing the particles and the enveloping material. The particles are obtained by spraying a fluid mixture of the components through a nozzle or by a spray disc, and cooling. The stabilized particles of active materials can be incorporated with percompounds and other washing composition components.