LAVIOSA ARGIMEL® B4 Rheological Additive for Low to Medium Polarity Solvent-Borne Systems. LAVIOSA ARGIMEL® B4 is a rheological additive for solvent-borne systems of low to medium polarity that gives thixotropic effect, sag control, excellent leveling, and prevents pigments from long-term storage settling. The nature of LAVIOSA ARGIMEL® B4 is a bentonite clay organically modified with a quaternary alkylammonium compound.