Further development on the water diffusion dating of archaeological obsidian tools, based on Fick's law of diffusion, is presented. It involves (a) a reassessment of surface saturation layer location and (b) a novel in-house made MATLAB software with reference to the age sensitivity of the SS layer, and the propagation of errors. So far, 11 dates have been produced for archaeological obsidian tools over the World and the SIMS-SS ages with present software versus archaeological and mean radiocarbon ages were in excellent concordance. (c) 2006 Published by Elsevier B.V.