Chemical compositions such as adhesive, sealing or coating compositions containing one or more microencapsulated ingredients are activated by directly contacting an ultrasonic device (2) to the composition (8) and sonicating the composition to rupture the microcapsules. The method may be carried out in a sonication chamber (1) in which the ultrasonic device (2) is immersed in the composition (8) and from which the composition flows before it sets. Alternatively the ultrasonic energy may be applied to the composition in situ.