Abstract: A system for cleaning a substrate with a foam performs a method for generating a cleaning foam. In the first operation of the method, the system pumps a fluid into a premix chamber. The premix chamber is a component of a male plug which fits into a female housing in the system. Then the system injects a gas into the premix chamber to initiate generation of the foam from the fluid. The foam flows from the premix chamber into a sealed helical channel formed by a helical indentation on an outside surface of the male plug and an inner surface of the female housing to allow the foam to reach a desired state along a length of the sealed helical channel. In the last operation of the method, the foam outputs from an exit end of the helical channel through the male plug to a component of the system.