Paint Drying More Interesting Than We Thought

The phrase "like watching paint dry" is no doubt still apropos in some situations, but researchers have found that the actual mechanism of drying paint is not as we assumed.
By considering how the particles push against each other, the researchers worked out that the inward velocity of a particle is proportional to the square of its diameter. For the paint, large particles should therefore move 49 times faster than the small particles – something that was observed experimentally.

Understanding this effect, Fortini says, could lead to a range of useful materials. "This type of 'self-layering' in a coating could be very useful," he says. "In a sunscreen, most of the sunlight-blocking particles could be designed to push their way to the top, leaving particles that can adhere to the skin near the bottom of the coating."