A sugar coating is formed on a multiplicity of items (5) such as confectionery, using a suspension of crystal nuclei in a solution of sugar. This suspension is created by ultrasonic irradiation of a supersaturated solution. For example a saturated solution is cooled, and stored in a tank (16) connected to a recirculation (10) loop (18) containing a pump (24) and an ultrasonic irradiation module (26). Treated suspension (20) is withdrawn to coat items (11), and new supersaturated solution (14) is introduced. The sugar solution is sufficiently viscous to suppress crystal growth.