Abstract: A chemically stable solid surface coating modifier is provided by application to a substrate of a dispersion containing a highly dispersed hydrophobic powder, a silicon liquid, a solvent, and, optionally, an adhesive. The powder has been activated by alkali or alkaline salts and then treated with an organic silylating agent. The modifer is effective in imparting water repellent, anti-fouling, anti-icing, anti-corrosive, anti-friction properties to varies surfaces. The modifer also provides protection against other chemical, biological and atmospheric agents.