Predicting When Ketchup Will Start Flowing

Predicting When Ketchup Will Start FlowingFor a wide range of complex fluids, the transition from solid-like at rest to liquid-like when pushed can be predicted from properties of the at-rest state.By Philip Ball C omplex fluids such as ketchup or toothpaste can switch from a solid-like state to a liquid-like state when subjected to a stress, such as shaking or squeezing.The details of this change can be crucial in areas such as food science and cosmetics.A research team has now shown that the point at which the solid-to-liquid transition occurs can be predicted from the properties of the substance while it is still a solid [1].This insight could guide the design and control of this industrially important class of fluids.