The water level of PET bottle mineral waters sold on hot summer days seem to vary. This led us to simulate the high temperature condition (37℃) and examine the change in the quantity and quality of natural mineral water in unopened PET bottles. The results showed that approximately 1 g of water was lost per week when the bottle was kept unopened at 37℃. There was also a change in quality, due to precipitation of calcium carbonate, decline of hardness, and decrease of pH.
