1. Principle

There are two main approaches to wet granulation (figure 1 ).

In the main approach, a controlled amount of liquid is sprayed onto the dry powder, before or during granulation. This action creates liquid or solid bridges (after evaporation of the solvent) between the particles. The liquid forms contacts between the particles, enhancing their interaction and promoting their coarsening.

In a second, less common approach, droplets are formed from a suspension of the powder, which is then dried. Once the solvent has been removed, the end result is similar to that of the first approach. The processes used for this second approach are similar to spray-drying techniques. The only difference is that, here, the aim is to increase particle size rather than to dry the...