This helps the potatoes absorb excess steam that can make mashed potatoes watery. (inspiredtaste.net)
Adjustable steam vent holes provide easy evaporation to aid in the cooking and warming processes and keep the pan from overheating or filling with excess steam. (geekwrapped.com)
Leave them for about 5 minutes to absorb excess steam that can make mashed potatoes watery. (inspiredtaste.net)