a dry thickness after the subsequent condensation of from about 200 u00b0 u00e5 to 50 u03bcm depending on the particular qualities desired and the particular emdiment for example the dry coating thickness is preferably from about 0 5 u03bcm to 10 u03bcm for the purpose of reducing the rate of surface defects from about 5 to 50 u03bcm for the purpose of flattening the base surface from about 0 1 to 10 u03bcm for the purpose of preventing precipitation or from about 0 2 to 10 u03bcm for the purpose of protecting a plastic base from moisture a generally suitable thickness of the coating film is preferably from about 0 1 to 50 u03bcm and more preferably from about 0 5 to 10 u03bcm after the compound of formula i is coated onto the surface of a base to form a coating layer the coating layer is subjected to heat treatment to form a polysiloxane coating film the heat treatment for condensation is usually carried out at a temperature ranging from about 100 u00b0 c to 500 u00b0 c but at a temperature such that heating does not deform or soften the base when glass is used as a base the heat treatment is preferably effected at a temperature of from about 400 u00b0 c to 480 u00b0 c for about 30 minutes in order to prevent the base from melting or deforming during the heat treatment a method for heating only the coating layer can be employed according to such the method the heat treatment is carried out using a surface heating.