NOVELTY - Dispersion comprises 0.1-25 wt.% of hydrophobic silicic acid, 8-90 wt.% of at least one alcohol (including ethanol, 1-propanol and 2-propanol), 7-89 wt.% of water, 0-30 wt.% of solvent that is immiscible in water, and 0.04-5 wt.% of at least one carboxy vinyl polymer, which is present in the neutralized form.    USE - The dispersion is useful for modifying a surface with hydrophobic silicic acid, where the surface is: solid surfaces; hard, non-porous surfaces including glass, glazed ceramic, metal, plastic and painted surfaces; and flexible surfaces such as leather, paper or textiles. The dispersion is useful for modifying the surface including treating the automotive coatings and vehicle parts to avoid further soiling after washing and to achieve cleaning of the surface by rain, and treating building facades, roofs, windows and exterior solar cells.    ADVANTAGE - The dispersion imparts water-repelling and self-cleaning properties to the surface, where the water-repelling effect prevents or delays the growth of bacteria and fungi on the surface. The neutralized carboxyvinyl (having low water content, high solubility and good thickening effect) provides improved storage stability and workability of the dispersion.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for:    (1) modifying a surface with hydrophobic silicic acid, comprising applying the above dispersion on the surface by a drip-free application method; and    (2) preparing the above dispersion, comprising either (a) grinding particles of hydrophobic silicic acid (having an average value of particle size distribution of 50-800, preferably 50-200 nm) in a suspension which includes at least one alcohol (such as ethanol, 1-propanol and 2-propanol) and at least one silazane compound of formula ((R1R2R3Si)2NR4) (I) or (cyclo-(R1R2SiNR4)m) (II), (b) preparing a concentrated aqueous solution of a neutralized carboxy vinyl polymer, (c) adding the obtained solution to a medium comprising more than 60 wt.% of at least one alcohol such as ethanol, 1-propanol and 2-propanol, and (d) adding the suspension obtained from the step (a) to the mixture obtained from the step (c), or the steps (a) and (b) alone.    R1-R3 = 1-12C hydrocarbon;    R4 = H or CH3; and    m = 3-8.