Abstract: A process control system especially adapted for mixing and supplying fountain solution to printing press apparatus obviates the need for mechanical float metering devices and scale mechanisms heretofore used for mixing of liquid solution ingredients in prescribed ratios, by providing an electrical circuit control system for measuring the quantity of liquid ingredients to be mixed and for controlling the sequence in which the ingredients are transferred between a plurality of mixing and holding tanks. A selectively variable time base is correlated with the quantity of a primary liquid ingredient introduced to a mixing tank and an electrical sensing device is operative to detect the presence of a quantity of fountain solution within the tank corresponding to a batch thereof.