Obsidian hydration is not effective on surfaces that are uneven due to gradual weathering caused by natural forces.The volcanic glass of Obsidian Cliff in Yellowstone National Park is a National Historic Landmark, and was an important source of raw material for the manufacture of stone tools by Native Americans.
to frequencies of their co-occurrence in specific contexts Ordering of physical remains in a series so that adjacent items in the series are more similar to each other than items farther apart. Relies on principally measuring changes in proportional abundance, or frequency, of ceramic style.
Ordering of artifacts according to their frequencies so that the distribution conforms to a "battleship-shaped" curve.
At now fine grains method is applied in our laboratory, but in future also the quartz inclusion grains procedure will be implemented.
After an experimental comparison between chemical preparations of the samples reported in literature, the procedure described in  was adopted, being the one that gave the best results on objects of known age even if the material is of poor quality.
The principle behind obsidian hydration dating is simple—the longer the artifact surface has been exposed, the thicker the hydration band will be.