Specific boiling recommendations for mouthguards vary by manufacturer, but the conventional boiling time is approximately 30 seconds. Some providers direct users through a multi-step boiling process that results in a total of around 1 minute of boiling.
The goal of boiling the mouthguard is to make it flexible for molding. Some manufacturers direct users to dip the boiled guard in cold water for a few seconds. Others simply say to remove it from water for about 20 seconds to allow cooling. After boiling, the guard becomes flimsy enough to allow the user to place it in his mouth and bite down for molding.