Physicists Unspool What Happens When Fabrics Dry

"Watching paint dry" may be a term most people use to show how boring something can be, but the physics of what happens when anything changes from wet to dry is enough to grab scientists' attention. No, really -- there are still many unanswered questions about drying. Now, a new paper looks at exactly how the drying process works in tiny detail.

The research, published in the journal Physical Review Applied in February, uses a technique called nuclear magnetic resonance spectroscopy to measure the distribution of water in a material. The results could help researchers understand how moisture behaves in a variety of contexts -- from humidity in a house's insulation to drying clothes after washing.

"With all these tools, we are able to effectively determine the law of absorption that has been so unknown," said Philippe Coussot, a research engineer at Gustave Eiffel University in France. "This basic approach is just the first step to be able to more systematically determine the real kinetic equation for absorption."

In a wet piece of fabric, water can either be bound to the structure of the fabric or circulate as vapor in between the weave. Coussot and colleagues put samples of wet fabric into open-topped containers and exposed them to dry air flows. Then, they used nuclear magnetic resonance to make measurements of the quantity of water bound to the fabric at different times and determined the overall drying rate.