There is occasionally a pressure buildup inside the shaker. One might also experience that certain, sudden temperature change cause difficulty in the removal of the lid from the jar, but do not panic, it will separate. Another tip would be not to allow the shaker to stand fully assembled while not in use, this will cause the stagnation of air, it looks great, but the drinks don't taste great. This shaker (also aptly named cream-shaker), is used mainly for the preparation of dairybased cocktails, which are referred to as after-Dinner drinks.