Triphenylmethane colour (Sicovit Patent blue) and Colanyl green were used as colouring agent for droplet penetration experiments in amounts of 0.3 w/w% and 0.1 w/w% respectively. Sodium carboxymethylcellulose (purity > 99.5 %) was used as thickener in the droplet penetration and morphology experiments in concentrations up to 5.2 w/w% in order to investigate the influence of increasing the coating solution viscosity. The principle of a coated granule composition can be seen in Fig. 2. Ideally the sodium sulphate core is completely covered with a layer of coated sodium sulphate in the fluid bed coating process. The small amount of the dextrin binder in the coating layer enhances the adhesion of the sodium sulphate coating layer to the core surface. Such granule compositions are typically