We have determined the temporal history of the pressure of a confined low-temperature plasma generated under conditions of modest laser intensity (0.05–1 GW/cm2) by utilizing the target as a thin witness plate to interferometrically measure the particle velocity at its rear surface. The observed data are in agreement with a simple ideal gas model describing the behavior of the plasma. A 150-ns duration laser-driver pulse can deliver a multikilobar pressure ramp to a condensed phase sample for dynamic high-pressure studies.