cylindrical chamber approximately 16 inches long and 11 16 inch in diameter for each experiment the test chamber was filled with a mixture of water and elastic hollow particles and care was taken to minimize the amount of air remaining in the chamber a digital pressure gauge measured the pressure applied to the test samples while a linear voltage displacement transducer lvdt on the drive screw measured the applied volume change this experiment involved two pressure cycles up to 10 000 psi of an 11 6 mixture in volume of a sample of polypropylene hollow particles sample 1 and water the elastic hollow particles used for this experiment had an outside diameter of 2 5 mm and a variable size cavity microscopic exploration revealed that the size of the cavity was minimal as a result the pressure volume curve as shown in fig3 was very similar to that obtained in an experiment involving only the compression of water and residual air this experiment involved two pressure cycles of a 5 6 mixture in volume of another sample of polypropylene elastic hollow particles sample 2 and water results are shown in fig4 the polypropylene elastic hollow particles had a 10 mm diameter and a 1 mm wall thickness the sound of the elastic hollow particles collapsing could be heard under the increasing pressure as seen in the pressure volume response every collapsed particle provided additional volume and relieved the pressure in the chamber most of.