According to a first aspect of the invention, a process is provided for the preparation of amorphous particles comprising a homogeneous distribution of one or more dyes encapsulated by an amorphous, siliceous encapsulating agent, the process comprising: (a) providing a precursor of the encapsulating agent in liquid form; (b) providing the one or more dyes in liquid form; (c) mixing the liquid forms; (d) aerosolizing the mixture to form droplets comprising the one or more dyes and encapsulating agent; and (e) heating the droplets to form the particles comprising the one or more dyes encapsulated by the siliceous encapsulating agent; wherein at least one of the liquid forms provided is aqueous and the or each aqueous liquid form is acidic. According to a second aspect of the invention, encapsulated dyes made by the process of the first aspect of the invention are provided.