, the water flow continued until almost the entire water column was drained. Moreover, it was observed that in a constant pressure head, the flow rate increased by time till a steady condition was reached. In an actual fuel cell, water is produced constantly As such, in this experiment the flow rate of 2 ml min−1 was maintained and the maximum pressure, Pmax, was recorded. To investigate any hysteresis effects, the tested samples were dried as described previously. The same experiment is then repeated on the dried GDLs, the average values of the permeation threshold are listed in Table 2.