Abstract: A mill for grinding marking particles utilizing a source of a pressurized fluid is provided. The mill includes a grinding chamber having a peripheral wall, a base and a central axis. The mill also includes a nozzle associated with the peripheral wall of the grinding chamber. The nozzle defines an inlet of the nozzle. The inlet is connectable to the source of pressurized fluid. The pressurized fluid propels the marking particles about the periphery of the chamber. The mill further includes a plug cooperable with the nozzle. The plug is in engagement the nozzle when the pressure within the grinding chamber is substantially greater than the pressure at the inlet of the nozzle.