'Coffee-Ring Effect' Could Reveal What's in Your Tap Water

Tap-water droplets from two buildings on the Michigan State University campus leave behind different coffee-ring patterns; "hard" water is shown on the left, and water treated with a softener is shown on the right.
(Image credit: Xiaoyan Li)

The physics of the so-called "coffee-ring effect" — how particles in liquid cause darkened areas to form at the perimeter of a spill — is helping scientists to quickly and cheaply identify the mineral contents of tap water, according to new research.

Residues left behind when tap water evaporates are "like fingerprints" for the water's properties and contents, Rebecca Lahr, an assistant professor in the chemistry department in Lyman Briggs College at Michigan State University, told the American Chemical Society (ACS) in a statement.

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Mindy Weisberger
Live Science Contributor

Mindy Weisberger is a science journalist and author of "Rise of the Zombie Bugs: The Surprising Science of Parasitic Mind-Control" (Hopkins Press). She formerly edited for Scholastic and was a channel editor and senior writer for Live Science. She has reported on general science, covering climate change, paleontology, biology and space. Mindy studied film at Columbia University; prior to LS, she produced, wrote and directed media for the American Museum of Natural History in NYC. Her videos about dinosaurs, astrophysics, biodiversity and evolution appear in museums and science centers worldwide, earning awards such as the CINE Golden Eagle and the Communicator Award of Excellence. Her writing has also appeared in Scientific American, The Washington Post, How It Works Magazine and CNN.