This paper reports observation of universal scaling of physical properties of clay particles, Laponite (aspect ratio = 30) (L) and Na Montmorillonite (MMT, aspect ratio = 200), in aqueous alcohol solutions (methanol, ethanol and 1-propanol) with solvent polarity, defined through reaction field factor f(OH)(epsilon(0),n) = [(epsilon 0 - 1/epsilon(0) + 2) - (n(2) - 1/n(2) + 2)], at room temperature (20 degrees C). Here, epsilon(0) and n are the static dielectric constant and refractive index of the solvent concerned. Physical properties (Z) such as zeta potential, effective aggregate size, viscosity and surface tension scaled with the relative solvent polarity as Z similar to delta f(alpha); delta f = (f(w)(epsilon(0), n) - f(OH)(epsilon(0), n)), where f(w)(epsilon(0), n) is the reaction field factor for water, Z is the normalized physical property, and alpha is its characteristic scaling exponent. The value of this exponent was found to be invariant of aspect ratio of the clay but dependent on the solvent polarity only. (C) 2011 Elsevier Inc. All rights reserved.