In many cases, cavitation disappears at higher pressures than those at which it first appears. A measure of this cavitation hysteresis is the cavitation-delay time which tends to decrease with an increase in velocity, size, dissolved air content, or liquid tension. Cavitation hysteresis is a random phenomenon and is also dependent upon flow history and surface characteristics. Liquid tensions of one atmosphere are quite common and tensions of two to three atmospheres may be sustained for several seconds.