A pressure release mechanism for use with a capsule for processing materials or growing crystals in supercritical fluids is disclosed. The capsule with the pressure release mechanism is scalable up to very large volumes and is cost effective according to a preferred embodiment. In conjunction with suitable high pressure apparatus, the capsule with pressure release mechanism is capable of processing materials at pressures and temperatures of 20-2000 MPa and 25-1500° C., respectively. Of course, there can be other variations, modifications, and alternatives.