A number of source-specific obsidian hydration rates are proposed for California obsidian sources. Based on these findings, two major modifications are suggested as refinements of the present obsidian hydration dating technique: (1) source-specific obsidian hydration rates should be determined for individual obsidian sources within a given geographic region, and (2) which will necessitate the identification of the source of each obsidian artefact for greater precision of obsidian hydration dating results. -- AATA