levigazione

Levigazione, or levigation, is a process used to reduce the particle size of a solid by grinding it with a liquid in which the solid has little to no solubility. The term derives from the idea of smoothing or smoothing out the powder during size reduction.

In practice, a liquid acting as a levigating agent is added to the solid to form a paste or slurry that facilitates grinding and helps prevent agglomeration and friction. This approach contrasts with dry grinding (trituration) and with procedures that first grind dry and then remove solvent.

Applications of levigation occur in several fields. In pharmaceutical compounding and cosmetics, it is used to prepare semi-solid dosage forms and ointments by wetting powders so they can be uniformly incorporated into bases. In ceramics and mineral processing, levigation produces uniform slurries for grinding pigments, clays, or ores, aiding dispersion and particle size control.

Common levigating agents are non-solvents or poorly soluble liquids chosen for compatibility with the material and the intended final product. Examples include mineral oil, glycerin, castor oil, propylene glycol, and water under conditions where the solid is not appreciably soluble. The agent must wet the particles without reacting with them, and residual solvent may be removed if a dry powder is required.

Limitations include potential chemical interactions with the active material, difficulty removing the levigating agent from the final product, and the need to balance viscosity and handling properties. Levigation is often complemented by other size-reduction methods such as milling or jet milling when very fine or uniform particle distributions are required.