In order for the powder to granulate, it must be moistened to a certain degree. For this purpose, the powders are mixed with granulating liquids. The optimum amount of humectant is determined experimentally (based on the physical and chemical properties of the powders) and specified in the regulations. If there is not enough humectant, the granules will crumble after drying, if there is a lot of humectant, the mass will be viscous, sticky and poorly granulated. A mass with optimum moisture content is a moist, dense mixture that does not stick to the hand, but crumbles into individual lumps when squeezed. Binders are necessary to bind the powder particles and prevent surface disruption of the finished tablets, i.e. to increase the strength of the tablets and their resistance to fracture. The binder (granulating) liquid hits the solid powder particles, wetting them and forming liquid “bridges”.

During dehydration of the mixture of active and auxiliary substances with granulating liquid, the binding liquid “bridges” gradually turn into solid “bridges” and as a result agglomerates (final granules having the structure of a “snowball”) are formed. Particles are brought together by molecular, electrostatic and capillary forces. The formation of “bridges” can occur through chemical reactions. Wet granulation remains the most widely used method for the manufacture of tablet mixtures. There are at least four different variations of the method: Granulation of drug and excipient mixtures using a binder solution. Granulation of drug and excipient mixture with binder and pure solvent.
Granulation of a mixture of drug and excipients and part of the binder using a solution of the remaining binder.