Abstract: A mechanically pressurized aerosol dispensing system comprising a cap which houses a piston, an actuator moveably attached to the cap, forming together with the cap a dispensing head assembly, and an expandable elastic reservoir. The system is fitted over a standard container holding a liquid product, and includes a dip tube assembly to draw liquid into the dispensing head assembly, where the contents are released through the dispensing head assembly, via the aerosol nozzle and valve. A twist of the threaded cap raises a piston, thereby opening a charging chamber within the dispensing head assembly. This creates a vacuum with the resulting suction pulling the product up through the dip tube to fill the charging chamber. Twisting the cap in the opposite direction lowers the piston in a downstroke which closes the charging chamber, forcing the product into the expandable elastic reservoir where it is then discharged through the nozzle.