Washington: When a coffee stain dries, its edges become noticeably darker and thicker, while the middle of the stain remains almost unsoiled.This is called the "coffee ring effect", and it occurs because the coffee particles move toward the edge of the stain while the water in the liquid evaporates. At a microscopic level, this coffee ring effect can also be seen in liquids with particles of other materials such as plastic and wood.Researchers from the Departments of Chemical Engineering and Chemistry at KU Leuven have now discovered how to counteract coffee rings with `surfactants`, i.e. soap.
Women`s immune systems remain younger for longer
Competition with rivals boosts male testosterone level