wet granulation

Wet granulation turns a fine, dusty powder into small free-flowing clumps by wetting it, letting the particles glue together, and then drying. It is much like making damp sand stick into little balls before it dries hard — except the goal is a powder that flows and compresses better.

In practice you mix the drug and excipients, add a liquid binder solution while the mass is stirred or kneaded, and the moist powder builds up into granules. The wet mass is then forced through a screen to size it, dried in an oven or fluid-bed dryer, milled to a uniform size, blended with a lubricant, and finally compressed. Granulation improves powder flow, prevents fine particles from separating, and increases the density so a given dose fits a smaller tablet.

The main caveat is that adding water and heat can degrade drugs that are sensitive to moisture or warmth, and the process has many steps and high energy cost. For such drugs, dry granulation or direct compression is preferred.