A thread structure of an aerator for a water faucet, wherein based on the pitch, the major diameter and the pitch diameter of the metric and imperial threads of water faucets and the variation tolerance, universal measurements of the corresponding pitch, major diameter and pitch diameter and the variation tolerance for the aerator are calculated. The dispenser includes a handle coupled to a pair of nesting roller members each having a plurality of openings with one roller member being rotatable between a position where the plurality of apertures are aligned to allow the flow of decontaminant from within the inner nesting roller member and where the plurality of apertures are not aligned to prevent the flow of decontaminant. The amount of energy to provide to each of the print head elements during a print head cycle to produce a spot having the desired density is calculated based on: the desired density to be produced by the print head element during the print head cycle, and the predicted temperature of the print head element at the beginning of the print head cycle.