A method of treating a surface of an object comprising a rubber material and in particular a bladder for use in a process for making a vehicle tire. The method comprises subjecting the surface to a gas at a low pressure at which the gas is susceptible of forming plasma, and causing the gas to form plasma. In order to obtain repellent properties of the surface of the rubber material fluorine gas such as tetrafluormethane or hexafluorethane is used. Preferably the treatment is performed until there is obtained a surface layer of the rubber material with properties modified by the treatment having an expected lifetime corresponding to the expected lifetime of the object.