Plate impact experiments were performed on B270 glass in order to measure the properties of post-failure wave material. The initial failure wave velocity is 1.27 km/s . After the material is released, the failure wave velocity drops to 0.65 km/s. At a stress of 6.72 GPa, the sound speed in the failed material is 4.97 km/s (compare to 5.79 km/s in the intact material) with a density comparable to the predicted shock value. At a stress of 0.26 GPa, the average sound speed in the failed material is 3.55 km/s, and the density drops to 65% of the intact value. The spall strength of the failed material is greater than 0.14 GPa.