The time required for an interferometric modulator to switch from a state with a collapsed cavity to a state with an open cavity or vice versa, i.e., the switch time, is decreased by decreasing the viscosity of the gas filling the cavity. The viscosity is decreased by forming at least a partial vacuum in the cavity. The partial vacuum is formed, in turn, by forming a cavity in a housing holding the interferometric modulator. The vacuum can be generated by a vacuum pump. By decreasing the switch time, interferometric modulators in an array of interferometric modulators can be switched more quickly, thereby advantageously increasing the refresh rate for a display using the array.