Watching paint dry may seem excruciatingly boring, but a new international study found that the process of drying may actually be the key to the improvement of everyday products, from paint to sunscreen.

A team of scientists from the University of Surrey, in collaboration with Université Claude Bernard Lyon 1, discovered how paint particles separate according to size whenever wet coatings turn dry.

The research team used material experiment and computer simulations to show how it happens.

The Science Behind Drying Paint

When paint dries, smaller microscopic particles work together to push the larger ones away, and therefore creates two layers. The smaller particles remain at the top surface while the larger particles are pushed to the bottom, scientists said.

Study lead author Dr. Andrea Fortini from the University of Surrey said paint, ink or the outer layers on tablets work by spreading liquid with solid particles onto the surface, allowing the liquid to evaporate.

This is not new, Fortini said, but what was exciting was that the "self-layering" mechanism happens naturally. It could be very useful in finding out how effective products such as sunscreen are.

In sunscreen, scientists said majority of the particles that block out sunlight could be engineered to push their way to the top surface. Particles on the bottom could become stickier and adhere better to the skin.

"Typically, the particles used in coatings have sizes that are 1,000 times smaller than the width of a human hair, so engineering these coatings takes place at a microscopic level," said Fortini.

The research team will perform further investigations in order to understand how to control the width of the layer by manipulating the type and amount of small particles in the coating.

It will be tested in industrial products such as inks, paint and adhesive, as well as in cosmetics and pharmaceuticals. The new research is published in the journal Physical Review Letters.

The Universe Is Like Cracking Paint

Drying paint doesn't only go through self-layering processes. Paint shrinks as it dries and creates tension all over the entire system. As it cracks, it relieves the built-up internal tension.

Duke University scientists said that when this happens, large and small structures alike are formed from the cracking paint. The process is actually hierarchal and follows a pattern called "constructal law."

It could then be used to explain the size differences between the celestial bodies across the universe, researchers said.

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